The current implementation has a couple of shortcomings:
- It fails to handle hybrid systems correctly.
- The APIC registration code which handles CPU number assignents is in
the middle of the APIC code and detached from the topology evaluation.
- The various mechanisms which enumerate APICs, ACPI, MPPARSE and guest
specific ones, tweak global variables as they see fit or in case of
XENPV just hack around the generic mechanisms completely.
- The CPUID topology evaluation code is sprinkled all over the vendor
code and reevaluates global variables on every hotplug operation.
- There is no way to analyze topology on the boot CPU before bringing up
the APs. This causes problems for infrastructure like PERF which needs
to size certain aspects upfront or could be simplified if that would be
possible.
- The APIC admission and CPU number association logic is incomprehensible
and overly complex and needs to be kept around after boot instead of
completing this right after the APIC enumeration.
This update addresses these shortcomings with the following changes:
- Rework the CPUID evaluation code so it is common for all vendors and
provides information about the APIC ID segments in a uniform way
independent of the number of segments (Thread, Core, Module, ..., Die,
Package) so that this information can be computed instead of rewriting
global variables of dubious value over and over.
- A few cleanups and simplifcations of the APIC, IO/APIC and related
interfaces to prepare for the topology evaluation changes.
- Seperation of the parser stages so the early evaluation which tries to
find the APIC address can be seperately overridden from the late
evaluation which enumerates and registers the local APIC as further
preparation for sanitizing the topology evaluation.
- A new registration and admission logic which
- encapsulates the inner workings so that parsers and guest logic
cannot longer fiddle in it
- uses the APIC ID segments to build topology bitmaps at registration
time
- provides a sane admission logic
- allows to detect the crash kernel case, where CPU0 does not run on
the real BSP, automatically. This is required to prevent sending
INIT/SIPI sequences to the real BSP which would reset the whole
machine. This was so far handled by a tedious command line
parameter, which does not even work in nested crash scenarios.
- Associates CPU number after the enumeration completed and prevents
the late registration of APICs, which was somehow tolerated before.
- Converting all parsers and guest enumeration mechanisms over to the
new interfaces.
This allows to get rid of all global variable tweaking from the parsers
and enumeration mechanisms and sanitizes the XEN[PV] handling so it can
use CPUID evaluation for the first time.
- Mopping up existing sins by taking the information from the APIC ID
segment bitmaps.
This evaluates hybrid systems correctly on the boot CPU and allows for
cleanups and fixes in the related drivers, e.g. PERF.
The series has been extensively tested and the minimal late fallout due to
a broken ACPI/MADT table has been addressed by tightening the admission
logic further.
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Merge tag 'x86-apic-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 APIC updates from Thomas Gleixner:
"Rework of APIC enumeration and topology evaluation.
The current implementation has a couple of shortcomings:
- It fails to handle hybrid systems correctly.
- The APIC registration code which handles CPU number assignents is
in the middle of the APIC code and detached from the topology
evaluation.
- The various mechanisms which enumerate APICs, ACPI, MPPARSE and
guest specific ones, tweak global variables as they see fit or in
case of XENPV just hack around the generic mechanisms completely.
- The CPUID topology evaluation code is sprinkled all over the vendor
code and reevaluates global variables on every hotplug operation.
- There is no way to analyze topology on the boot CPU before bringing
up the APs. This causes problems for infrastructure like PERF which
needs to size certain aspects upfront or could be simplified if
that would be possible.
- The APIC admission and CPU number association logic is
incomprehensible and overly complex and needs to be kept around
after boot instead of completing this right after the APIC
enumeration.
This update addresses these shortcomings with the following changes:
- Rework the CPUID evaluation code so it is common for all vendors
and provides information about the APIC ID segments in a uniform
way independent of the number of segments (Thread, Core, Module,
..., Die, Package) so that this information can be computed instead
of rewriting global variables of dubious value over and over.
- A few cleanups and simplifcations of the APIC, IO/APIC and related
interfaces to prepare for the topology evaluation changes.
- Seperation of the parser stages so the early evaluation which tries
to find the APIC address can be seperately overridden from the late
evaluation which enumerates and registers the local APIC as further
preparation for sanitizing the topology evaluation.
- A new registration and admission logic which
- encapsulates the inner workings so that parsers and guest logic
cannot longer fiddle in it
- uses the APIC ID segments to build topology bitmaps at
registration time
- provides a sane admission logic
- allows to detect the crash kernel case, where CPU0 does not run
on the real BSP, automatically. This is required to prevent
sending INIT/SIPI sequences to the real BSP which would reset
the whole machine. This was so far handled by a tedious command
line parameter, which does not even work in nested crash
scenarios.
- Associates CPU number after the enumeration completed and
prevents the late registration of APICs, which was somehow
tolerated before.
- Converting all parsers and guest enumeration mechanisms over to the
new interfaces.
This allows to get rid of all global variable tweaking from the
parsers and enumeration mechanisms and sanitizes the XEN[PV]
handling so it can use CPUID evaluation for the first time.
- Mopping up existing sins by taking the information from the APIC ID
segment bitmaps.
This evaluates hybrid systems correctly on the boot CPU and allows
for cleanups and fixes in the related drivers, e.g. PERF.
The series has been extensively tested and the minimal late fallout
due to a broken ACPI/MADT table has been addressed by tightening the
admission logic further"
* tag 'x86-apic-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (76 commits)
x86/topology: Ignore non-present APIC IDs in a present package
x86/apic: Build the x86 topology enumeration functions on UP APIC builds too
smp: Provide 'setup_max_cpus' definition on UP too
smp: Avoid 'setup_max_cpus' namespace collision/shadowing
x86/bugs: Use fixed addressing for VERW operand
x86/cpu/topology: Get rid of cpuinfo::x86_max_cores
x86/cpu/topology: Provide __num_[cores|threads]_per_package
x86/cpu/topology: Rename topology_max_die_per_package()
x86/cpu/topology: Rename smp_num_siblings
x86/cpu/topology: Retrieve cores per package from topology bitmaps
x86/cpu/topology: Use topology logical mapping mechanism
x86/cpu/topology: Provide logical pkg/die mapping
x86/cpu/topology: Simplify cpu_mark_primary_thread()
x86/cpu/topology: Mop up primary thread mask handling
x86/cpu/topology: Use topology bitmaps for sizing
x86/cpu/topology: Let XEN/PV use topology from CPUID/MADT
x86/xen/smp_pv: Count number of vCPUs early
x86/cpu/topology: Assign hotpluggable CPUIDs during init
x86/cpu/topology: Reject unknown APIC IDs on ACPI hotplug
x86/topology: Add a mechanism to track topology via APIC IDs
...
- The hierarchical timer pull model
When timer wheel timers are armed they are placed into the timer wheel
of a CPU which is likely to be busy at the time of expiry. This is done
to avoid wakeups on potentially idle CPUs.
This is wrong in several aspects:
1) The heuristics to select the target CPU are wrong by
definition as the chance to get the prediction right is close
to zero.
2) Due to #1 it is possible that timers are accumulated on a
single target CPU
3) The required computation in the enqueue path is just overhead for
dubious value especially under the consideration that the vast
majority of timer wheel timers are either canceled or rearmed
before they expire.
The timer pull model avoids the above by removing the target
computation on enqueue and queueing timers always on the CPU on which
they get armed.
This is achieved by having separate wheels for CPU pinned timers and
global timers which do not care about where they expire.
As long as a CPU is busy it handles both the pinned and the global
timers which are queued on the CPU local timer wheels.
When a CPU goes idle it evaluates its own timer wheels:
- If the first expiring timer is a pinned timer, then the global
timers can be ignored as the CPU will wake up before they expire.
- If the first expiring timer is a global timer, then the expiry time
is propagated into the timer pull hierarchy and the CPU makes sure
to wake up for the first pinned timer.
The timer pull hierarchy organizes CPUs in groups of eight at the
lowest level and at the next levels groups of eight groups up to the
point where no further aggregation of groups is required, i.e. the
number of levels is log8(NR_CPUS). The magic number of eight has been
established by experimention, but can be adjusted if needed.
In each group one busy CPU acts as the migrator. It's only one CPU to
avoid lock contention on remote timer wheels.
The migrator CPU checks in its own timer wheel handling whether there
are other CPUs in the group which have gone idle and have global timers
to expire. If there are global timers to expire, the migrator locks the
remote CPU timer wheel and handles the expiry.
Depending on the group level in the hierarchy this handling can require
to walk the hierarchy downwards to the CPU level.
Special care is taken when the last CPU goes idle. At this point the
CPU is the systemwide migrator at the top of the hierarchy and it
therefore cannot delegate to the hierarchy. It needs to arm its own
timer device to expire either at the first expiring timer in the
hierarchy or at the first CPU local timer, which ever expires first.
This completely removes the overhead from the enqueue path, which is
e.g. for networking a true hotpath and trades it for a slightly more
complex idle path.
This has been in development for a couple of years and the final series
has been extensively tested by various teams from silicon vendors and
ran through extensive CI.
There have been slight performance improvements observed on network
centric workloads and an Intel team confirmed that this allows them to
power down a die completely on a mult-die socket for the first time in
a mostly idle scenario.
There is only one outstanding ~1.5% regression on a specific overloaded
netperf test which is currently investigated, but the rest is either
positive or neutral performance wise and positive on the power
management side.
- Fixes for the timekeeping interpolation code for cross-timestamps:
cross-timestamps are used for PTP to get snapshots from hardware timers
and interpolated them back to clock MONOTONIC. The changes address a
few corner cases in the interpolation code which got the math and logic
wrong.
- Simplifcation of the clocksource watchdog retry logic to automatically
adjust to handle larger systems correctly instead of having more
incomprehensible command line parameters.
- Treewide consolidation of the VDSO data structures.
- The usual small improvements and cleanups all over the place.
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Merge tag 'timers-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"A large set of updates and features for timers and timekeeping:
- The hierarchical timer pull model
When timer wheel timers are armed they are placed into the timer
wheel of a CPU which is likely to be busy at the time of expiry.
This is done to avoid wakeups on potentially idle CPUs.
This is wrong in several aspects:
1) The heuristics to select the target CPU are wrong by
definition as the chance to get the prediction right is
close to zero.
2) Due to #1 it is possible that timers are accumulated on
a single target CPU
3) The required computation in the enqueue path is just overhead
for dubious value especially under the consideration that the
vast majority of timer wheel timers are either canceled or
rearmed before they expire.
The timer pull model avoids the above by removing the target
computation on enqueue and queueing timers always on the CPU on
which they get armed.
This is achieved by having separate wheels for CPU pinned timers
and global timers which do not care about where they expire.
As long as a CPU is busy it handles both the pinned and the global
timers which are queued on the CPU local timer wheels.
When a CPU goes idle it evaluates its own timer wheels:
- If the first expiring timer is a pinned timer, then the global
timers can be ignored as the CPU will wake up before they
expire.
- If the first expiring timer is a global timer, then the expiry
time is propagated into the timer pull hierarchy and the CPU
makes sure to wake up for the first pinned timer.
The timer pull hierarchy organizes CPUs in groups of eight at the
lowest level and at the next levels groups of eight groups up to
the point where no further aggregation of groups is required, i.e.
the number of levels is log8(NR_CPUS). The magic number of eight
has been established by experimention, but can be adjusted if
needed.
In each group one busy CPU acts as the migrator. It's only one CPU
to avoid lock contention on remote timer wheels.
The migrator CPU checks in its own timer wheel handling whether
there are other CPUs in the group which have gone idle and have
global timers to expire. If there are global timers to expire, the
migrator locks the remote CPU timer wheel and handles the expiry.
Depending on the group level in the hierarchy this handling can
require to walk the hierarchy downwards to the CPU level.
Special care is taken when the last CPU goes idle. At this point
the CPU is the systemwide migrator at the top of the hierarchy and
it therefore cannot delegate to the hierarchy. It needs to arm its
own timer device to expire either at the first expiring timer in
the hierarchy or at the first CPU local timer, which ever expires
first.
This completely removes the overhead from the enqueue path, which
is e.g. for networking a true hotpath and trades it for a slightly
more complex idle path.
This has been in development for a couple of years and the final
series has been extensively tested by various teams from silicon
vendors and ran through extensive CI.
There have been slight performance improvements observed on network
centric workloads and an Intel team confirmed that this allows them
to power down a die completely on a mult-die socket for the first
time in a mostly idle scenario.
There is only one outstanding ~1.5% regression on a specific
overloaded netperf test which is currently investigated, but the
rest is either positive or neutral performance wise and positive on
the power management side.
- Fixes for the timekeeping interpolation code for cross-timestamps:
cross-timestamps are used for PTP to get snapshots from hardware
timers and interpolated them back to clock MONOTONIC. The changes
address a few corner cases in the interpolation code which got the
math and logic wrong.
- Simplifcation of the clocksource watchdog retry logic to
automatically adjust to handle larger systems correctly instead of
having more incomprehensible command line parameters.
- Treewide consolidation of the VDSO data structures.
- The usual small improvements and cleanups all over the place"
* tag 'timers-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (62 commits)
timer/migration: Fix quick check reporting late expiry
tick/sched: Fix build failure for CONFIG_NO_HZ_COMMON=n
vdso/datapage: Quick fix - use asm/page-def.h for ARM64
timers: Assert no next dyntick timer look-up while CPU is offline
tick: Assume timekeeping is correctly handed over upon last offline idle call
tick: Shut down low-res tick from dying CPU
tick: Split nohz and highres features from nohz_mode
tick: Move individual bit features to debuggable mask accesses
tick: Move got_idle_tick away from common flags
tick: Assume the tick can't be stopped in NOHZ_MODE_INACTIVE mode
tick: Move broadcast cancellation up to CPUHP_AP_TICK_DYING
tick: Move tick cancellation up to CPUHP_AP_TICK_DYING
tick: Start centralizing tick related CPU hotplug operations
tick/sched: Don't clear ts::next_tick again in can_stop_idle_tick()
tick/sched: Rename tick_nohz_stop_sched_tick() to tick_nohz_full_stop_tick()
tick: Use IS_ENABLED() whenever possible
tick/sched: Remove useless oneshot ifdeffery
tick/nohz: Remove duplicate between lowres and highres handlers
tick/nohz: Remove duplicate between tick_nohz_switch_to_nohz() and tick_setup_sched_timer()
hrtimer: Select housekeeping CPU during migration
...
The cross-timestamp mechanism which allows to correlate hardware
clocks uses clocksource pointers for describing the correlation.
That's suboptimal as drivers need to obtain the pointer, which requires
needless exports and exposing internals.
This can be completely avoided by assigning clocksource IDs and using
them for describing the correlated clock source.
This update adds clocksource IDs to all clocksources in the tree which
can be exposed to this mechanism and removes the pointer and now needless
exports.
This is separate from the timer core changes as it was provided to the
PTP folks to build further changes on top.
A related improvement for the core and the correlation handling has not
made it this time, but is expected to get ready for the next round.
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Merge tag 'timers-ptp-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull clocksource updates from Thomas Gleixner:
"Updates for timekeeping and PTP core.
The cross-timestamp mechanism which allows to correlate hardware
clocks uses clocksource pointers for describing the correlation.
That's suboptimal as drivers need to obtain the pointer, which
requires needless exports and exposing internals. This can all be
completely avoided by assigning clocksource IDs and using them for
describing the correlated clock source.
So this adds clocksource IDs to all clocksources in the tree which can
be exposed to this mechanism and removes the pointer and now needless
exports.
A related improvement for the core and the correlation handling has
not made it this time, but is expected to get ready for the next
round"
* tag 'timers-ptp-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
kvmclock: Unexport kvmclock clocksource
treewide: Remove system_counterval_t.cs, which is never read
timekeeping: Evaluate system_counterval_t.cs_id instead of .cs
ptp/kvm, arm_arch_timer: Set system_counterval_t.cs_id to constant
x86/kvm, ptp/kvm: Add clocksource ID, set system_counterval_t.cs_id
x86/tsc: Add clocksource ID, set system_counterval_t.cs_id
timekeeping: Add clocksource ID to struct system_counterval_t
x86/tsc: Correct kernel-doc notation
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Merge tag 'smp-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull cpu core updates from Thomas Gleixner:
"A small boring set of cleanups for the SMP and CPU hotplug code"
* tag 'smp-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
cpu: Remove stray semicolon
smp: Make __smp_processor_id() 0-argument macro
cpu: Mark cpu_possible_mask as __ro_after_init
kernel/cpu: Convert snprintf() to sysfs_emit()
cpu/hotplug: Delete an extraneous kernel-doc description
- Core and platform-MSI
The core changes have been adopted from previous work which converted
ARM[64] to the new per device MSI domain model, which was merged to
support multiple MSI domain per device. The ARM[64] changes are being
worked on too, but have not been ready yet. The core and platform-MSI
changes have been split out to not hold up RISC-V and to avoid that
RISC-V builds on the scheduled for removal interfaces.
The core support provides new interfaces to handle wire to MSI bridges
in a straight forward way and introduces new platform-MSI interfaces
which are built on top of the per device MSI domain model.
Once ARM[64] is converted over the old platform-MSI interfaces and the
related ugliness in the MSI core code will be removed.
- Drivers:
- Add a new driver for the Andes hart-level interrupt controller
- Rework the SiFive PLIC driver to prepare for MSI suport
- Expand the RISC-V INTC driver to support the new RISC-V AIA
controller which provides the basis for MSI on RISC-V
- A few fixup for the fallout of the core changes.
The actual MSI parts for RISC-V were finalized late and have been
post-poned for the next merge window.
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Merge tag 'irq-msi-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull MSI updates from Thomas Gleixner:
"Updates for the MSI interrupt subsystem and initial RISC-V MSI
support.
The core changes have been adopted from previous work which converted
ARM[64] to the new per device MSI domain model, which was merged to
support multiple MSI domain per device. The ARM[64] changes are being
worked on too, but have not been ready yet. The core and platform-MSI
changes have been split out to not hold up RISC-V and to avoid that
RISC-V builds on the scheduled for removal interfaces.
The core support provides new interfaces to handle wire to MSI bridges
in a straight forward way and introduces new platform-MSI interfaces
which are built on top of the per device MSI domain model.
Once ARM[64] is converted over the old platform-MSI interfaces and the
related ugliness in the MSI core code will be removed.
The actual MSI parts for RISC-V were finalized late and have been
post-poned for the next merge window.
Drivers:
- Add a new driver for the Andes hart-level interrupt controller
- Rework the SiFive PLIC driver to prepare for MSI suport
- Expand the RISC-V INTC driver to support the new RISC-V AIA
controller which provides the basis for MSI on RISC-V
- A few fixup for the fallout of the core changes"
* tag 'irq-msi-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (29 commits)
irqchip/riscv-intc: Fix low-level interrupt handler setup for AIA
x86/apic/msi: Use DOMAIN_BUS_GENERIC_MSI for HPET/IO-APIC domain search
genirq/matrix: Dynamic bitmap allocation
irqchip/riscv-intc: Add support for RISC-V AIA
irqchip/sifive-plic: Improve locking safety by using irqsave/irqrestore
irqchip/sifive-plic: Parse number of interrupts and contexts early in plic_probe()
irqchip/sifive-plic: Cleanup PLIC contexts upon irqdomain creation failure
irqchip/sifive-plic: Use riscv_get_intc_hwnode() to get parent fwnode
irqchip/sifive-plic: Use devm_xyz() for managed allocation
irqchip/sifive-plic: Use dev_xyz() in-place of pr_xyz()
irqchip/sifive-plic: Convert PLIC driver into a platform driver
irqchip/riscv-intc: Introduce Andes hart-level interrupt controller
irqchip/riscv-intc: Allow large non-standard interrupt number
genirq/irqdomain: Don't call ops->select for DOMAIN_BUS_ANY tokens
irqchip/imx-intmux: Handle pure domain searches correctly
genirq/msi: Provide MSI_FLAG_PARENT_PM_DEV
genirq/irqdomain: Reroute device MSI create_mapping
genirq/msi: Provide allocation/free functions for "wired" MSI interrupts
genirq/msi: Optionally use dev->fwnode for device domain
genirq/msi: Provide DOMAIN_BUS_WIRED_TO_MSI
...
- Core:
- Make affinity changes immediately effective for interrupt
threads. This reduces the impact on isolated CPUs as it pulls over the
thread right away instead of doing it after the next hardware
interrupt arrived.
- Cleanup and improvements for the interrupt chip simulator
- Deduplication of the interrupt descriptor initialization code so the
sparse and non-sparse mode share more code.
- Drivers:
- A set of conversions to platform_drivers::remove_new() which gets rid
of the pointless return value.
- A new driver for the Starfive JH8100 SoC
- Support for Amlogic-T7 SoCs
- Improvement for the interrupt handling and EOI management for the
loongson interrupt controller.
- The usual fixes and improvements all over the place.
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Merge tag 'irq-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull irq updates from Thomas Gleixner:
"Core:
- Make affinity changes take effect immediately for interrupt
threads. This reduces the impact on isolated CPUs as it pulls over
the thread right away instead of doing it after the next hardware
interrupt arrived.
- Cleanup and improvements for the interrupt chip simulator
- Deduplication of the interrupt descriptor initialization code so
the sparse and non-sparse mode share more code.
Drivers:
- A set of conversions to platform_drivers::remove_new() which gets
rid of the pointless return value.
- A new driver for the Starfive JH8100 SoC
- Support for Amlogic-T7 SoCs
- Improvement for the interrupt handling and EOI management for the
loongson interrupt controller.
- The usual fixes and improvements all over the place"
* tag 'irq-core-2024-03-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits)
irqchip/ts4800: Convert to platform_driver::remove_new() callback
irqchip/stm32-exti: Convert to platform_driver::remove_new() callback
irqchip/renesas-rza1: Convert to platform_driver::remove_new() callback
irqchip/renesas-irqc: Convert to platform_driver::remove_new() callback
irqchip/renesas-intc-irqpin: Convert to platform_driver::remove_new() callback
irqchip/pruss-intc: Convert to platform_driver::remove_new() callback
irqchip/mvebu-pic: Convert to platform_driver::remove_new() callback
irqchip/madera: Convert to platform_driver::remove_new() callback
irqchip/ls-scfg-msi: Convert to platform_driver::remove_new() callback
irqchip/keystone: Convert to platform_driver::remove_new() callback
irqchip/imx-irqsteer: Convert to platform_driver::remove_new() callback
irqchip/imx-intmux: Convert to platform_driver::remove_new() callback
irqchip/imgpdc: Convert to platform_driver::remove_new() callback
irqchip: Add StarFive external interrupt controller
dt-bindings: interrupt-controller: Add starfive,jh8100-intc
arm64: dts: Add gpio_intc node for Amlogic-T7 SoCs
irqchip/meson-gpio: Add support for Amlogic-T7 SoCs
dt-bindings: interrupt-controller: Add support for Amlogic-T7 SoCs
irqchip/vic: Fix a kernel-doc warning
genirq: Wake interrupt threads immediately when changing affinity
...
A quiet cycle. One trivial doc update patch. Two patches to drop now defunct
memory_spread_slab feature from cgroup1 cpuset.
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Merge tag 'cgroup-for-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
"A quiet cycle. One trivial doc update patch. Two patches to drop the
now defunct memory_spread_slab feature from cgroup1 cpuset"
* tag 'cgroup-for-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup/cpuset: Mark memory_spread_slab as obsolete
cgroup/cpuset: Remove cpuset_do_slab_mem_spread()
docs: cgroup-v1: add missing code-block tags
This pull request contains two patches that convert tasklet users to BH
workqueue - backtractest and usb hcd. DM conversions are being routed
through the respective subsystem tree. Hopefully, the next cycle will see a
lot more conversions.
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Merge tag 'wq-for-6.9-bh-conversions' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
Pull workqueue BH conversions from Tejun Heo:
"This contains two patches that convert tasklet users to BH workqueues:
backtracetest and usb hcd.
DM conversions are being routed through the respective subsystem tree.
Hopefully, the next cycle will see a lot more conversions"
* tag 'wq-for-6.9-bh-conversions' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
usb: core: hcd: Convert from tasklet to BH workqueue
backtracetest: Convert from tasklet to BH workqueue
This cycle, a lot of workqueue changes including some that are significant
and invasive.
- During v6.6 cycle, unbound workqueues were updated so that they are more
topology aware and flexible, which among other things improved workqueue
behavior on modern multi-L3 CPUs. In the process, 636b927eba
("workqueue: Make unbound workqueues to use per-cpu pool_workqueues")
switched unbound workqueues to use per-CPU frontend pool_workqueues as a
part of increasing front-back mapping flexibility.
An unwelcome side effect of this change was that this made max concurrency
enforcement per-CPU blowing up the maximum number of allowed concurrent
executions. I incorrectly assumed that this wouldn't cause practical
problems as most unbound workqueue users are self-regulate max
concurrency; however, there definitely are which don't (e.g. on IO paths)
and the drastic increase in the allowed max concurrency led to noticeable
perf regressions in some use cases.
This is now addressed by separating out max concurrency enforcement to a
separate struct - wq_node_nr_active - which makes @max_active consistently
mean system-wide max concurrency regardless of the number of CPUs or
(finally) NUMA nodes. This is a rather invasive and, in places, a bit
clunky; however, the clunkiness rises from the the inherent requirement to
handle the disagreement between the execution locality domain and max
concurrency enforcement domain on some modern machines. See 5797b1c189
("workqueue: Implement system-wide nr_active enforcement for unbound
workqueues") for more details.
- BH workqueue support is added. They are similar to per-CPU workqueues but
execute work items in the softirq context. This is expected to replace
tasklet. However, currently, it's missing the ability to disable and
enable work items which is needed to convert many tasklet users. To avoid
crowding this merge window too much, this will be included in the next
merge window. A separate pull request will be sent for the couple
conversion patches that are currently pending.
- Waiman plugged a long-standing hole in workqueue CPU isolation where
ordered workqueues didn't follow wq_unbound_cpumask updates. Ordered
workqueues now follow the same rules as other unbound workqueues.
- More CPU isolation improvements: Juri fixed another deficit in workqueue
isolation where unbound rescuers don't respect wq_unbound_cpumask.
Leonardo fixed delayed_work timers firing on isolated CPUs.
- Other misc changes.
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Merge tag 'wq-for-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
Pull workqueue updates from Tejun Heo:
"This cycle, a lot of workqueue changes including some that are
significant and invasive.
- During v6.6 cycle, unbound workqueues were updated so that they are
more topology aware and flexible, which among other things improved
workqueue behavior on modern multi-L3 CPUs. In the process, commit
636b927eba ("workqueue: Make unbound workqueues to use per-cpu
pool_workqueues") switched unbound workqueues to use per-CPU
frontend pool_workqueues as a part of increasing front-back mapping
flexibility.
An unwelcome side effect of this change was that this made max
concurrency enforcement per-CPU blowing up the maximum number of
allowed concurrent executions. I incorrectly assumed that this
wouldn't cause practical problems as most unbound workqueue users
are self-regulate max concurrency; however, there definitely are
which don't (e.g. on IO paths) and the drastic increase in the
allowed max concurrency led to noticeable perf regressions in some
use cases.
This is now addressed by separating out max concurrency enforcement
to a separate struct - wq_node_nr_active - which makes @max_active
consistently mean system-wide max concurrency regardless of the
number of CPUs or (finally) NUMA nodes. This is a rather invasive
and, in places, a bit clunky; however, the clunkiness rises from
the the inherent requirement to handle the disagreement between the
execution locality domain and max concurrency enforcement domain on
some modern machines.
See commit 5797b1c189 ("workqueue: Implement system-wide
nr_active enforcement for unbound workqueues") for more details.
- BH workqueue support is added.
They are similar to per-CPU workqueues but execute work items in
the softirq context. This is expected to replace tasklet. However,
currently, it's missing the ability to disable and enable work
items which is needed to convert many tasklet users. To avoid
crowding this merge window too much, this will be included in the
next merge window. A separate pull request will be sent for the
couple conversion patches that are currently pending.
- Waiman plugged a long-standing hole in workqueue CPU isolation
where ordered workqueues didn't follow wq_unbound_cpumask updates.
Ordered workqueues now follow the same rules as other unbound
workqueues.
- More CPU isolation improvements: Juri fixed another deficit in
workqueue isolation where unbound rescuers don't respect
wq_unbound_cpumask. Leonardo fixed delayed_work timers firing on
isolated CPUs.
- Other misc changes"
* tag 'wq-for-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: (54 commits)
workqueue: Drain BH work items on hot-unplugged CPUs
workqueue: Introduce from_work() helper for cleaner callback declarations
workqueue: Control intensive warning threshold through cmdline
workqueue: Make @flags handling consistent across set_work_data() and friends
workqueue: Remove clear_work_data()
workqueue: Factor out work_grab_pending() from __cancel_work_sync()
workqueue: Clean up enum work_bits and related constants
workqueue: Introduce work_cancel_flags
workqueue: Use variable name irq_flags for saving local irq flags
workqueue: Reorganize flush and cancel[_sync] functions
workqueue: Rename __cancel_work_timer() to __cancel_timer_sync()
workqueue: Use rcu_read_lock_any_held() instead of rcu_read_lock_held()
workqueue: Cosmetic changes
workqueue, irq_work: Build fix for !CONFIG_IRQ_WORK
workqueue: Fix queue_work_on() with BH workqueues
async: Use a dedicated unbound workqueue with raised min_active
workqueue: Implement workqueue_set_min_active()
workqueue: Fix kernel-doc comment of unplug_oldest_pwq()
workqueue: Bind unbound workqueue rescuer to wq_unbound_cpumask
kernel/workqueue: Let rescuers follow unbound wq cpumask changes
...
This pull request contains the following branches:
rcu-doc.2024.02.14a: Documentation updates.
rcu-nocb.2024.02.14a: RCU NOCB updates, code cleanups, unnecessary
barrier removals and minor bug fixes.
rcu-exp.2024.02.14a: RCU exp, fixing a circular dependency between
workqueue and RCU expedited callback handling.
rcu-tasks.2024.02.26a: RCU tasks, avoiding deadlocks in do_exit() when
calling synchronize_rcu_task() with a mutex hold, maintaining
real-time response in rcu_tasks_postscan() and a minor
fix for tasks trace quiescence check.
rcu-misc.2024.02.14a: Misc updates, comments and readibility
improvement, boot time parameter for lazy RCU and rcutorture
improvement.
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Merge tag 'rcu.next.v6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux
Pull RCU updates from Boqun Feng:
- Eliminate deadlocks involving do_exit() and RCU tasks, by Paul:
Instead of SRCU read side critical sections, now a percpu list is
used in do_exit() for scaning yet-to-exit tasks
- Fix a deadlock due to the dependency between workqueue and RCU
expedited grace period, reported by Anna-Maria Behnsen and Thomas
Gleixner and fixed by Frederic: Now RCU expedited always uses its own
kthread worker instead of a workqueue
- RCU NOCB updates, code cleanups, unnecessary barrier removals and
minor bug fixes
- Maintain real-time response in rcu_tasks_postscan() and a minor fix
for tasks trace quiescence check
- Misc updates, comments and readibility improvement, boot time
parameter for lazy RCU and rcutorture improvement
- Documentation updates
* tag 'rcu.next.v6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux: (34 commits)
rcu-tasks: Maintain real-time response in rcu_tasks_postscan()
rcu-tasks: Eliminate deadlocks involving do_exit() and RCU tasks
rcu-tasks: Maintain lists to eliminate RCU-tasks/do_exit() deadlocks
rcu-tasks: Initialize data to eliminate RCU-tasks/do_exit() deadlocks
rcu-tasks: Initialize callback lists at rcu_init() time
rcu-tasks: Add data to eliminate RCU-tasks/do_exit() deadlocks
rcu-tasks: Repair RCU Tasks Trace quiescence check
rcu/sync: remove un-used rcu_sync_enter_start function
rcutorture: Suppress rtort_pipe_count warnings until after stalls
srcu: Improve comments about acceleration leak
rcu: Provide a boot time parameter to control lazy RCU
rcu: Rename jiffies_till_flush to jiffies_lazy_flush
doc: Update checklist.rst discussion of callback execution
doc: Clarify use of slab constructors and SLAB_TYPESAFE_BY_RCU
context_tracking: Fix kerneldoc headers for __ct_user_{enter,exit}()
doc: Add EARLY flag to early-parsed kernel boot parameters
doc: Add CONFIG_RCU_STRICT_GRACE_PERIOD to checklist.rst
doc: Make checklist.rst note that spinlocks are implied RCU readers
doc: Make whatisRCU.rst note that spinlocks are RCU readers
doc: Spinlocks are implied RCU readers
...
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Merge tag 'vfs-6.9.super' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull block handle updates from Christian Brauner:
"Last cycle we changed opening of block devices, and opening a block
device would return a bdev_handle. This allowed us to implement
support for restricting and forbidding writes to mounted block
devices. It was accompanied by converting and adding helpers to
operate on bdev_handles instead of plain block devices.
That was already a good step forward but ultimately it isn't necessary
to have special purpose helpers for opening block devices internally
that return a bdev_handle.
Fundamentally, opening a block device internally should just be
equivalent to opening files. So now all internal opens of block
devices return files just as a userspace open would. Instead of
introducing a separate indirection into bdev_open_by_*() via struct
bdev_handle bdev_file_open_by_*() is made to just return a struct
file. Opening and closing a block device just becomes equivalent to
opening and closing a file.
This all works well because internally we already have a pseudo fs for
block devices and so opening block devices is simple. There's a few
places where we needed to be careful such as during boot when the
kernel is supposed to mount the rootfs directly without init doing it.
Here we need to take care to ensure that we flush out any asynchronous
file close. That's what we already do for opening, unpacking, and
closing the initramfs. So nothing new here.
The equivalence of opening and closing block devices to regular files
is a win in and of itself. But it also has various other advantages.
We can remove struct bdev_handle completely. Various low-level helpers
are now private to the block layer. Other helpers were simply
removable completely.
A follow-up series that is already reviewed build on this and makes it
possible to remove bdev->bd_inode and allows various clean ups of the
buffer head code as well. All places where we stashed a bdev_handle
now just stash a file and use simple accessors to get to the actual
block device which was already the case for bdev_handle"
* tag 'vfs-6.9.super' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (35 commits)
block: remove bdev_handle completely
block: don't rely on BLK_OPEN_RESTRICT_WRITES when yielding write access
bdev: remove bdev pointer from struct bdev_handle
bdev: make struct bdev_handle private to the block layer
bdev: make bdev_{release, open_by_dev}() private to block layer
bdev: remove bdev_open_by_path()
reiserfs: port block device access to file
ocfs2: port block device access to file
nfs: port block device access to files
jfs: port block device access to file
f2fs: port block device access to files
ext4: port block device access to file
erofs: port device access to file
btrfs: port device access to file
bcachefs: port block device access to file
target: port block device access to file
s390: port block device access to file
nvme: port block device access to file
block2mtd: port device access to files
bcache: port block device access to files
...
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Merge tag 'vfs-6.9.pidfd' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull pdfd updates from Christian Brauner:
- Until now pidfds could only be created for thread-group leaders but
not for threads. There was no technical reason for this. We simply
had no users that needed support for this. Now we do have users that
need support for this.
This introduces a new PIDFD_THREAD flag for pidfd_open(). If that
flag is set pidfd_open() creates a pidfd that refers to a specific
thread.
In addition, we now allow clone() and clone3() to be called with
CLONE_PIDFD | CLONE_THREAD which wasn't possible before.
A pidfd that refers to an individual thread differs from a pidfd that
refers to a thread-group leader:
(1) Pidfds are pollable. A task may poll a pidfd and get notified
when the task has exited.
For thread-group leader pidfds the polling task is woken if the
thread-group is empty. In other words, if the thread-group
leader task exits when there are still threads alive in its
thread-group the polling task will not be woken when the
thread-group leader exits but rather when the last thread in the
thread-group exits.
For thread-specific pidfds the polling task is woken if the
thread exits.
(2) Passing a thread-group leader pidfd to pidfd_send_signal() will
generate thread-group directed signals like kill(2) does.
Passing a thread-specific pidfd to pidfd_send_signal() will
generate thread-specific signals like tgkill(2) does.
The default scope of the signal is thus determined by the type
of the pidfd.
Since use-cases exist where the default scope of the provided
pidfd needs to be overriden the following flags are added to
pidfd_send_signal():
- PIDFD_SIGNAL_THREAD
Send a thread-specific signal.
- PIDFD_SIGNAL_THREAD_GROUP
Send a thread-group directed signal.
- PIDFD_SIGNAL_PROCESS_GROUP
Send a process-group directed signal.
The scope change will only work if the struct pid is actually
used for this scope.
For example, in order to send a thread-group directed signal the
provided pidfd must be used as a thread-group leader and
similarly for PIDFD_SIGNAL_PROCESS_GROUP the struct pid must be
used as a process group leader.
- Move pidfds from the anonymous inode infrastructure to a tiny pseudo
filesystem. This will unblock further work that we weren't able to do
simply because of the very justified limitations of anonymous inodes.
Moving pidfds to a tiny pseudo filesystem allows for statx on pidfds
to become useful for the first time. They can now be compared by
inode number which are unique for the system lifetime.
Instead of stashing struct pid in file->private_data we can now stash
it in inode->i_private. This makes it possible to introduce concepts
that operate on a process once all file descriptors have been closed.
A concrete example is kill-on-last-close. Another side-effect is that
file->private_data is now freed up for per-file options for pidfds.
Now, each struct pid will refer to a different inode but the same
struct pid will refer to the same inode if it's opened multiple
times. In contrast to now where each struct pid refers to the same
inode.
The tiny pseudo filesystem is not visible anywhere in userspace
exactly like e.g., pipefs and sockfs. There's no lookup, there's no
complex inode operations, nothing. Dentries and inodes are always
deleted when the last pidfd is closed.
We allocate a new inode and dentry for each struct pid and we reuse
that inode and dentry for all pidfds that refer to the same struct
pid. The code is entirely optional and fairly small. If it's not
selected we fallback to anonymous inodes. Heavily inspired by nsfs.
The dentry and inode allocation mechanism is moved into generic
infrastructure that is now shared between nsfs and pidfs. The
path_from_stashed() helper must be provided with a stashing location,
an inode number, a mount, and the private data that is supposed to be
used and it will provide a path that can be passed to dentry_open().
The helper will try retrieve an existing dentry from the provided
stashing location. If a valid dentry is found it is reused. If not a
new one is allocated and we try to stash it in the provided location.
If this fails we retry until we either find an existing dentry or the
newly allocated dentry could be stashed. Subsequent openers of the
same namespace or task are then able to reuse it.
- Currently it is only possible to get notified when a task has exited,
i.e., become a zombie and userspace gets notified with EPOLLIN. We
now also support waiting until the task has been reaped, notifying
userspace with EPOLLHUP.
- Ensure that ESRCH is reported for getfd if a task is exiting instead
of the confusing EBADF.
- Various smaller cleanups to pidfd functions.
* tag 'vfs-6.9.pidfd' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (23 commits)
libfs: improve path_from_stashed()
libfs: add stashed_dentry_prune()
libfs: improve path_from_stashed() helper
pidfs: convert to path_from_stashed() helper
nsfs: convert to path_from_stashed() helper
libfs: add path_from_stashed()
pidfd: add pidfs
pidfd: move struct pidfd_fops
pidfd: allow to override signal scope in pidfd_send_signal()
pidfd: change pidfd_send_signal() to respect PIDFD_THREAD
signal: fill in si_code in prepare_kill_siginfo()
selftests: add ESRCH tests for pidfd_getfd()
pidfd: getfd should always report ESRCH if a task is exiting
pidfd: clone: allow CLONE_THREAD | CLONE_PIDFD together
pidfd: exit: kill the no longer used thread_group_exited()
pidfd: change do_notify_pidfd() to use __wake_up(poll_to_key(EPOLLIN))
pid: kill the obsolete PIDTYPE_PID code in transfer_pid()
pidfd: kill the no longer needed do_notify_pidfd() in de_thread()
pidfd_poll: report POLLHUP when pid_task() == NULL
pidfd: implement PIDFD_THREAD flag for pidfd_open()
...
This KUnit next update for Linux 6.9-rc1 consists of:
-- fix to make kunit_bus_type const
-- kunit tool change to Print UML command
-- DRM device creation helpers are now using the new kunit device
creation helpers. This change resulted in DRM helpers switching
from using a platform_device, to a dedicated bus and device type
used by kunit. kunit devices don't set DMA mask and this caused
regression on some drm tests as they can't allocate DMA buffers.
Fix this problem by setting DMA masks on the kunit device during
initialization.
-- KUnit has several macros which accept a log message, which can
contain printf format specifiers. Some of these (the explicit
log macros) already use the __printf() gcc attribute to ensure
the format specifiers are valid, but those which could fail the
test, and hence used __kunit_do_failed_assertion() behind the scenes,
did not.
These include: KUNIT_EXPECT_*_MSG(), KUNIT_ASSERT_*_MSG(), and
KUNIT_FAIL()
A 9 patch series adds the __printf() attribute, and fixes all of
the issues uncovered.
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Merge tag 'linux_kselftest-kunit-6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest
Pull KUnit updates from Shuah Khan:
- fix to make kunit_bus_type const
- kunit tool change to Print UML command
- DRM device creation helpers are now using the new kunit device
creation helpers. This change resulted in DRM helpers switching from
using a platform_device, to a dedicated bus and device type used by
kunit. kunit devices don't set DMA mask and this caused regression on
some drm tests as they can't allocate DMA buffers. Fix this problem
by setting DMA masks on the kunit device during initialization.
- KUnit has several macros which accept a log message, which can
contain printf format specifiers. Some of these (the explicit log
macros) already use the __printf() gcc attribute to ensure the format
specifiers are valid, but those which could fail the test, and hence
used __kunit_do_failed_assertion() behind the scenes, did not.
These include: KUNIT_EXPECT_*_MSG(), KUNIT_ASSERT_*_MSG(), and
KUNIT_FAIL()
A nine-patch series adds the __printf() attribute, and fixes all of
the issues uncovered.
* tag 'linux_kselftest-kunit-6.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
kunit: Annotate _MSG assertion variants with gnu printf specifiers
drm: tests: Fix invalid printf format specifiers in KUnit tests
drm/xe/tests: Fix printf format specifiers in xe_migrate test
net: test: Fix printf format specifier in skb_segment kunit test
rtc: test: Fix invalid format specifier.
time: test: Fix incorrect format specifier
lib: memcpy_kunit: Fix an invalid format specifier in an assertion msg
lib/cmdline: Fix an invalid format specifier in an assertion msg
kunit: test: Log the correct filter string in executor_test
kunit: Setup DMA masks on the kunit device
kunit: make kunit_bus_type const
kunit: Mark filter* params as rw
kunit: tool: Print UML command
- Do not allow large strings (> 4096) as single write to trace_marker
The size of a string written into trace_marker was determined by
the size of the sub-buffer in the ring buffer. That size is
dependent on the PAGE_SIZE of the architecture as it can be mapped
into user space. But on PowerPC, where PAGE_SIZE is 64K, that made
the limit of the string of writing into trace_marker 64K.
One of the selftests looks at the size of the ring buffer sub-buffers
and writes that plus more into the trace_marker. The write will take
what it can and report back what it consumed so that the user space
application (like echo) will write the rest of the string. The string
is stored in the ring buffer and can be read via the "trace" or
"trace_pipe" files.
The reading of the ring buffer uses vsnprintf(), which uses a precision
"%.*s" to make sure it only reads what is stored in the buffer, as
a bug could cause the string to be non terminated.
With the combination of the precision change and the PAGE_SIZE of 64K
allowing huge strings to be added into the ring buffer, plus the test
that would actually stress that limit, a bug was reported that
the precision used was too big for "%.*s" as the string was close to
64K in size and the max precision of vsnprintf is 32K.
Linus suggested not to have that precision as it could hide a bug
if the string was again stored without a nul byte.
Another issue that was brought up is that the trace_seq buffer is
also based on PAGE_SIZE even though it is not tied to the architecture
limit like the ring buffer sub-buffer is. Having it be 64K * 2 is
simply just too big and wasting memory on systems with 64K page sizes.
It is now hardcoded to 8K which is what all other architectures with
4K PAGE_SIZE has.
Finally, the write to trace_marker is now limited to 4K as there is no
reason to write larger strings into trace_marker.
- ring_buffer_wait() should not loop.
The ring_buffer_wait() does not have the full context (yet) on if it
should loop or not. Just exit the loop as soon as its woken up and
let the callers decide to loop or not (they already do, so it's a bit
redundant).
- Fix shortest_full field to be the smallest amount in the ring buffer that
a waiter is waiting for. The "shortest_full" field is updated when a new
waiter comes in and wants to wait for a smaller amount of data in the
ring buffer than other waiters. But after all waiters are woken up, it's
not reset, so if another waiter comes in wanting to wait for more data,
it will be woken up when the ring buffer has a smaller amount from what
the previous waiters were waiting for.
- The wake up all waiters on close is incorrectly called frome .release()
and not from .flush() so it will never wake up any waiters as the
.release() will not get called until all .read() calls are finished. And the
wakeup is for the waiters in those .read() calls.
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Merge tag 'trace-ring-buffer-v6.8-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing fixes from Steven Rostedt:
- Do not allow large strings (> 4096) as single write to trace_marker
The size of a string written into trace_marker was determined by the
size of the sub-buffer in the ring buffer. That size is dependent on
the PAGE_SIZE of the architecture as it can be mapped into user
space. But on PowerPC, where PAGE_SIZE is 64K, that made the limit of
the string of writing into trace_marker 64K.
One of the selftests looks at the size of the ring buffer sub-buffers
and writes that plus more into the trace_marker. The write will take
what it can and report back what it consumed so that the user space
application (like echo) will write the rest of the string. The string
is stored in the ring buffer and can be read via the "trace" or
"trace_pipe" files.
The reading of the ring buffer uses vsnprintf(), which uses a
precision "%.*s" to make sure it only reads what is stored in the
buffer, as a bug could cause the string to be non terminated.
With the combination of the precision change and the PAGE_SIZE of 64K
allowing huge strings to be added into the ring buffer, plus the test
that would actually stress that limit, a bug was reported that the
precision used was too big for "%.*s" as the string was close to 64K
in size and the max precision of vsnprintf is 32K.
Linus suggested not to have that precision as it could hide a bug if
the string was again stored without a nul byte.
Another issue that was brought up is that the trace_seq buffer is
also based on PAGE_SIZE even though it is not tied to the
architecture limit like the ring buffer sub-buffer is. Having it be
64K * 2 is simply just too big and wasting memory on systems with 64K
page sizes. It is now hardcoded to 8K which is what all other
architectures with 4K PAGE_SIZE has.
Finally, the write to trace_marker is now limited to 4K as there is
no reason to write larger strings into trace_marker.
- ring_buffer_wait() should not loop.
The ring_buffer_wait() does not have the full context (yet) on if it
should loop or not. Just exit the loop as soon as its woken up and
let the callers decide to loop or not (they already do, so it's a bit
redundant).
- Fix shortest_full field to be the smallest amount in the ring buffer
that a waiter is waiting for. The "shortest_full" field is updated
when a new waiter comes in and wants to wait for a smaller amount of
data in the ring buffer than other waiters. But after all waiters are
woken up, it's not reset, so if another waiter comes in wanting to
wait for more data, it will be woken up when the ring buffer has a
smaller amount from what the previous waiters were waiting for.
- The wake up all waiters on close is incorrectly called frome
.release() and not from .flush() so it will never wake up any waiters
as the .release() will not get called until all .read() calls are
finished. And the wakeup is for the waiters in those .read() calls.
* tag 'trace-ring-buffer-v6.8-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing: Use .flush() call to wake up readers
ring-buffer: Fix resetting of shortest_full
ring-buffer: Fix waking up ring buffer readers
tracing: Limit trace_marker writes to just 4K
tracing: Limit trace_seq size to just 8K and not depend on architecture PAGE_SIZE
tracing: Remove precision vsnprintf() check from print event
The .release() function does not get called until all readers of a file
descriptor are finished.
If a thread is blocked on reading a file descriptor in ring_buffer_wait(),
and another thread closes the file descriptor, it will not wake up the
other thread as ring_buffer_wake_waiters() is called by .release(), and
that will not get called until the .read() is finished.
The issue originally showed up in trace-cmd, but the readers are actually
other processes with their own file descriptors. So calling close() would wake
up the other tasks because they are blocked on another descriptor then the
one that was closed(). But there's other wake ups that solve that issue.
When a thread is blocked on a read, it can still hang even when another
thread closed its descriptor.
This is what the .flush() callback is for. Have the .flush() wake up the
readers.
Link: https://lore.kernel.org/linux-trace-kernel/20240308202432.107909457@goodmis.org
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linke li <lilinke99@qq.com>
Cc: Rabin Vincent <rabin@rab.in>
Fixes: f3ddb74ad0 ("tracing: Wake up ring buffer waiters on closing of the file")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The "shortest_full" variable is used to keep track of the waiter that is
waiting for the smallest amount on the ring buffer before being woken up.
When a tasks waits on the ring buffer, it passes in a "full" value that is
a percentage. 0 means wake up on any data. 1-100 means wake up from 1% to
100% full buffer.
As all waiters are on the same wait queue, the wake up happens for the
waiter with the smallest percentage.
The problem is that the smallest_full on the cpu_buffer that stores the
smallest amount doesn't get reset when all the waiters are woken up. It
does get reset when the ring buffer is reset (echo > /sys/kernel/tracing/trace).
This means that tasks may be woken up more often then when they want to
be. Instead, have the shortest_full field get reset just before waking up
all the tasks. If the tasks wait again, they will update the shortest_full
before sleeping.
Also add locking around setting of shortest_full in the poll logic, and
change "work" to "rbwork" to match the variable name for rb_irq_work
structures that are used in other places.
Link: https://lore.kernel.org/linux-trace-kernel/20240308202431.948914369@goodmis.org
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linke li <lilinke99@qq.com>
Cc: Rabin Vincent <rabin@rab.in>
Fixes: 2c2b0a78b3 ("ring-buffer: Add percentage of ring buffer full to wake up reader")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
A task can wait on a ring buffer for when it fills up to a specific
watermark. The writer will check the minimum watermark that waiters are
waiting for and if the ring buffer is past that, it will wake up all the
waiters.
The waiters are in a wait loop, and will first check if a signal is
pending and then check if the ring buffer is at the desired level where it
should break out of the loop.
If a file that uses a ring buffer closes, and there's threads waiting on
the ring buffer, it needs to wake up those threads. To do this, a
"wait_index" was used.
Before entering the wait loop, the waiter will read the wait_index. On
wakeup, it will check if the wait_index is different than when it entered
the loop, and will exit the loop if it is. The waker will only need to
update the wait_index before waking up the waiters.
This had a couple of bugs. One trivial one and one broken by design.
The trivial bug was that the waiter checked the wait_index after the
schedule() call. It had to be checked between the prepare_to_wait() and
the schedule() which it was not.
The main bug is that the first check to set the default wait_index will
always be outside the prepare_to_wait() and the schedule(). That's because
the ring_buffer_wait() doesn't have enough context to know if it should
break out of the loop.
The loop itself is not needed, because all the callers to the
ring_buffer_wait() also has their own loop, as the callers have a better
sense of what the context is to decide whether to break out of the loop
or not.
Just have the ring_buffer_wait() block once, and if it gets woken up, exit
the function and let the callers decide what to do next.
Link: https://lore.kernel.org/all/CAHk-=whs5MdtNjzFkTyaUy=vHi=qwWgPi0JgTe6OYUYMNSRZfg@mail.gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20240308202431.792933613@goodmis.org
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linke li <lilinke99@qq.com>
Cc: Rabin Vincent <rabin@rab.in>
Fixes: e30f53aad2 ("tracing: Do not busy wait in buffer splice")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
No solution yet for the stmmac issue mentioned in the last PR,
but it proved to be a lockdep false positive, not a blocker.
Current release - regressions:
- dpll: move all dpll<>netdev helpers to dpll code, fix build
regression with old compilers
Current release - new code bugs:
- page_pool: fix netlink dump stop/resume
Previous releases - regressions:
- bpf: fix verifier to check bpf_func_state->callback_depth when pruning
states as otherwise unsafe programs could get accepted
- ipv6: avoid possible UAF in ip6_route_mpath_notify()
- ice: reconfig host after changing MSI-X on VF
- mlx5:
- e-switch, change flow rule destination checking
- add a memory barrier to prevent a possible null-ptr-deref
- switch to using _bh variant of of spinlock where needed
Previous releases - always broken:
- netfilter: nf_conntrack_h323: add protection for bmp length out of range
- bpf: fix to zero-initialise xdp_rxq_info struct before running XDP
program in CPU map which led to random xdp_md fields
- xfrm: fix UDP encapsulation in TX packet offload
- netrom: fix data-races around sysctls
- ice:
- fix potential NULL pointer dereference in ice_bridge_setlink()
- fix uninitialized dplls mutex usage
- igc: avoid returning frame twice in XDP_REDIRECT
- i40e: disable NAPI right after disabling irqs when handling xsk_pool
- geneve: make sure to pull inner header in geneve_rx()
- sparx5: fix use after free inside sparx5_del_mact_entry
- dsa: microchip: fix register write order in ksz8_ind_write8()
Misc:
- selftests: mptcp: fixes for diag.sh
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Merge tag 'net-6.8-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Pull networking fixes from Paolo Abeni:
"Including fixes from bpf, ipsec and netfilter.
No solution yet for the stmmac issue mentioned in the last PR, but it
proved to be a lockdep false positive, not a blocker.
Current release - regressions:
- dpll: move all dpll<>netdev helpers to dpll code, fix build
regression with old compilers
Current release - new code bugs:
- page_pool: fix netlink dump stop/resume
Previous releases - regressions:
- bpf: fix verifier to check bpf_func_state->callback_depth when
pruning states as otherwise unsafe programs could get accepted
- ipv6: avoid possible UAF in ip6_route_mpath_notify()
- ice: reconfig host after changing MSI-X on VF
- mlx5:
- e-switch, change flow rule destination checking
- add a memory barrier to prevent a possible null-ptr-deref
- switch to using _bh variant of of spinlock where needed
Previous releases - always broken:
- netfilter: nf_conntrack_h323: add protection for bmp length out of
range
- bpf: fix to zero-initialise xdp_rxq_info struct before running XDP
program in CPU map which led to random xdp_md fields
- xfrm: fix UDP encapsulation in TX packet offload
- netrom: fix data-races around sysctls
- ice:
- fix potential NULL pointer dereference in ice_bridge_setlink()
- fix uninitialized dplls mutex usage
- igc: avoid returning frame twice in XDP_REDIRECT
- i40e: disable NAPI right after disabling irqs when handling
xsk_pool
- geneve: make sure to pull inner header in geneve_rx()
- sparx5: fix use after free inside sparx5_del_mact_entry
- dsa: microchip: fix register write order in ksz8_ind_write8()
Misc:
- selftests: mptcp: fixes for diag.sh"
* tag 'net-6.8-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (63 commits)
net: pds_core: Fix possible double free in error handling path
netrom: Fix data-races around sysctl_net_busy_read
netrom: Fix a data-race around sysctl_netrom_link_fails_count
netrom: Fix a data-race around sysctl_netrom_routing_control
netrom: Fix a data-race around sysctl_netrom_transport_no_activity_timeout
netrom: Fix a data-race around sysctl_netrom_transport_requested_window_size
netrom: Fix a data-race around sysctl_netrom_transport_busy_delay
netrom: Fix a data-race around sysctl_netrom_transport_acknowledge_delay
netrom: Fix a data-race around sysctl_netrom_transport_maximum_tries
netrom: Fix a data-race around sysctl_netrom_transport_timeout
netrom: Fix data-races around sysctl_netrom_network_ttl_initialiser
netrom: Fix a data-race around sysctl_netrom_obsolescence_count_initialiser
netrom: Fix a data-race around sysctl_netrom_default_path_quality
netfilter: nf_conntrack_h323: Add protection for bmp length out of range
netfilter: nf_tables: mark set as dead when unbinding anonymous set with timeout
netfilter: nft_ct: fix l3num expectations with inet pseudo family
netfilter: nf_tables: reject constant set with timeout
netfilter: nf_tables: disallow anonymous set with timeout flag
net/rds: fix WARNING in rds_conn_connect_if_down
net: dsa: microchip: fix register write order in ksz8_ind_write8()
...
Limit the max print event of trace_marker to just 4K string size. This must
also be less than the amount that can be held by a trace_seq along with
the text that is before the output (like the task name, PID, CPU, state,
etc). As trace_seq is made to handle large events (some greater than 4K).
Make the max size of a trace_marker write event be 4K which is guaranteed
to fit in the trace_seq buffer.
Link: https://lore.kernel.org/linux-trace-kernel/20240304223433.4ba47dff@gandalf.local.home
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
When a CPU is the last active in the hierarchy and it tries to enter
into idle, the quick check looking up the next event towards cpuidle
heuristics may report a too late expiry, such as in the following
scenario:
[GRP1:0]
migrator = NONE
active = NONE
nextevt = T0:0, T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = NONE migrator = NONE
active = NONE active = NONE
nextevt = T0, T1 nextevt = T2
/ \ / \
0 1 2 3
idle idle idle idle
0) The whole system is idle, and CPU 0 was the last migrator. CPU 0 has
a timer (T0), CPU 1 has a timer (T1) and CPU 2 has a timer (T2). The
expire order is T0 < T1 < T2.
[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = T0:0(i), T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = CPU0 migrator = NONE
active = CPU0 active = NONE
nextevt = T0(i), T1 nextevt = T2
/ \ / \
0 1 2 3
active idle idle idle
1) CPU 0 becomes active. The (i) means a now ignored timer.
[GRP1:0]
migrator = GRP0:0
active = GRP0:0
nextevt = T0:1
/ \
[GRP0:0] [GRP0:1]
migrator = CPU0 migrator = NONE
active = CPU0 active = NONE
nextevt = T1 nextevt = T2
/ \ / \
0 1 2 3
active idle idle idle
2) CPU 0 handles remote. No timer actually expired but ignored timers
have been cleaned out and their sibling's timers haven't been
propagated. As a result the top level's next event is T2 and not T1.
3) CPU 0 tries to enter idle without any global timer enqueued and calls
tmigr_quick_check(). The expiry of T2 is returned instead of the
expiry of T1.
When the quick check returns an expiry that is too late, the cpuidle
governor may pick up a C-state that is too deep. This may be result into
undesired CPU wake up latency if the next timer is actually close enough.
Fix this with assuming that expiries aren't sorted top-down while
performing the quick check. Pick up instead the earliest encountered one
while walking up the hierarchy.
7ee9887703 ("timers: Implement the hierarchical pull model")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240305002822.18130-1-frederic@kernel.org
When running an XDP program that is attached to a cpumap entry, we don't
initialise the xdp_rxq_info data structure being used in the xdp_buff
that backs the XDP program invocation. Tobias noticed that this leads to
random values being returned as the xdp_md->rx_queue_index value for XDP
programs running in a cpumap.
This means we're basically returning the contents of the uninitialised
memory, which is bad. Fix this by zero-initialising the rxq data
structure before running the XDP program.
Fixes: 9216477449 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap")
Reported-by: Tobias Böhm <tobias@aibor.de>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20240305213132.11955-1-toke@redhat.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
When comparing current and cached states verifier should consider
bpf_func_state->callback_depth. Current state cannot be pruned against
cached state, when current states has more iterations left compared to
cached state. Current state has more iterations left when it's
callback_depth is smaller.
Below is an example illustrating this bug, minimized from mailing list
discussion [0] (assume that BPF_F_TEST_STATE_FREQ is set).
The example is not a safe program: if loop_cb point (1) is followed by
loop_cb point (2), then division by zero is possible at point (4).
struct ctx {
__u64 a;
__u64 b;
__u64 c;
};
static void loop_cb(int i, struct ctx *ctx)
{
/* assume that generated code is "fallthrough-first":
* if ... == 1 goto
* if ... == 2 goto
* <default>
*/
switch (bpf_get_prandom_u32()) {
case 1: /* 1 */ ctx->a = 42; return 0; break;
case 2: /* 2 */ ctx->b = 42; return 0; break;
default: /* 3 */ ctx->c = 42; return 0; break;
}
}
SEC("tc")
__failure
__flag(BPF_F_TEST_STATE_FREQ)
int test(struct __sk_buff *skb)
{
struct ctx ctx = { 7, 7, 7 };
bpf_loop(2, loop_cb, &ctx, 0); /* 0 */
/* assume generated checks are in-order: .a first */
if (ctx.a == 42 && ctx.b == 42 && ctx.c == 7)
asm volatile("r0 /= 0;":::"r0"); /* 4 */
return 0;
}
Prior to this commit verifier built the following checkpoint tree for
this example:
.------------------------------------- Checkpoint / State name
| .-------------------------------- Code point number
| | .---------------------------- Stack state {ctx.a,ctx.b,ctx.c}
| | | .------------------- Callback depth in frame #0
v v v v
- (0) {7P,7P,7},depth=0
- (3) {7P,7P,7},depth=1
- (0) {7P,7P,42},depth=1
- (3) {7P,7,42},depth=2
- (0) {7P,7,42},depth=2 loop terminates because of depth limit
- (4) {7P,7,42},depth=0 predicted false, ctx.a marked precise
- (6) exit
(a) - (2) {7P,7,42},depth=2
- (0) {7P,42,42},depth=2 loop terminates because of depth limit
- (4) {7P,42,42},depth=0 predicted false, ctx.a marked precise
- (6) exit
(b) - (1) {7P,7P,42},depth=2
- (0) {42P,7P,42},depth=2 loop terminates because of depth limit
- (4) {42P,7P,42},depth=0 predicted false, ctx.{a,b} marked precise
- (6) exit
- (2) {7P,7,7},depth=1 considered safe, pruned using checkpoint (a)
(c) - (1) {7P,7P,7},depth=1 considered safe, pruned using checkpoint (b)
Here checkpoint (b) has callback_depth of 2, meaning that it would
never reach state {42,42,7}.
While checkpoint (c) has callback_depth of 1, and thus
could yet explore the state {42,42,7} if not pruned prematurely.
This commit makes forbids such premature pruning,
allowing verifier to explore states sub-tree starting at (c):
(c) - (1) {7,7,7P},depth=1
- (0) {42P,7,7P},depth=1
...
- (2) {42,7,7},depth=2
- (0) {42,42,7},depth=2 loop terminates because of depth limit
- (4) {42,42,7},depth=0 predicted true, ctx.{a,b,c} marked precise
- (5) division by zero
[0] https://lore.kernel.org/bpf/9b251840-7cb8-4d17-bd23-1fc8071d8eef@linux.dev/
Fixes: bb124da69c ("bpf: keep track of max number of bpf_loop callback iterations")
Suggested-by: Yonghong Song <yonghong.song@linux.dev>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240222154121.6991-2-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Two cpuset fixes. Both are for bugs in error handling paths and low risk.
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Merge tag 'cgroup-for-6.8-rc7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup fixes from Tejun Heo:
"Two cpuset fixes. Both are for bugs in error handling paths and low
risk"
* tag 'cgroup-for-6.8-rc7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup/cpuset: Fix retval in update_cpumask()
cgroup/cpuset: Fix a memory leak in update_exclusive_cpumask()
- fprobe: Fix to allocate entry_data_size buffer for each rethook
instance. This fixes a buffer overrun bug (which leads a kernel
crash) when fprobe user uses its entry_data in the entry_handler.
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Merge tag 'probes-fixes-v6.8-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull fprobe fix from Masami Hiramatsu:
- allocate entry_data_size buffer for each rethook instance.
This fixes a buffer overrun bug (which leads a kernel crash)
when fprobe user uses its entry_data in the entry_handler.
* tag 'probes-fixes-v6.8-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
fprobe: Fix to allocate entry_data_size buffer with rethook instances
Moving pidfds from the anonymous inode infrastructure to a separate tiny
in-kernel filesystem similar to sockfs, pipefs, and anon_inodefs causes
selinux denials and thus various userspace components that make heavy
use of pidfds to fail as pidfds used anon_inode_getfile() which aren't
subject to any LSM hooks. But dentry_open() is and that would cause
regressions.
The failures that are seen are selinux denials. But the core failure is
dbus-broker. That cascades into other services failing that depend on
dbus-broker. For example, when dbus-broker fails to start polkit and all
the others won't be able to work because they depend on dbus-broker.
The reason for dbus-broker failing is because it doesn't handle failures
for SO_PEERPIDFD correctly. Last kernel release we introduced
SO_PEERPIDFD (and SCM_PIDFD). SO_PEERPIDFD allows dbus-broker and polkit
and others to receive a pidfd for the peer of an AF_UNIX socket. This is
the first time in the history of Linux that we can safely authenticate
clients in a race-free manner.
dbus-broker immediately made use of this but messed up the error
checking. It only allowed EINVAL as a valid failure for SO_PEERPIDFD.
That's obviously problematic not just because of LSM denials but because
of seccomp denials that would prevent SO_PEERPIDFD from working; or any
other new error code from there.
So this is catching a flawed implementation in dbus-broker as well. It
has to fallback to the old pid-based authentication when SO_PEERPIDFD
doesn't work no matter the reasons otherwise it'll always risk such
failures. So overall that LSM denial should not have caused dbus-broker
to fail. It can never assume that a feature released one kernel ago like
SO_PEERPIDFD can be assumed to be available.
So, the next fix separate from the selinux policy update is to try and
fix dbus-broker at [3]. That should make it into Fedora as well. In
addition the selinux reference policy should also be updated. See [4]
for that. If Selinux is in enforcing mode in userspace and it encounters
anything that it doesn't know about it will deny it by default. And the
policy is entirely in userspace including declaring new types for stuff
like nsfs or pidfs to allow it.
For now we continue to raise S_PRIVATE on the inode if it's a pidfs
inode which means things behave exactly like before.
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2265630
Link: https://github.com/fedora-selinux/selinux-policy/pull/2050
Link: https://github.com/bus1/dbus-broker/pull/343 [3]
Link: https://github.com/SELinuxProject/refpolicy/pull/762 [4]
Reported-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240222190334.GA412503@dev-arch.thelio-3990X
Link: https://lore.kernel.org/r/20240218-neufahrzeuge-brauhaus-fb0eb6459771@brauner
Signed-off-by: Christian Brauner <brauner@kernel.org>
This moves pidfds from the anonymous inode infrastructure to a tiny
pseudo filesystem. This has been on my todo for quite a while as it will
unblock further work that we weren't able to do simply because of the
very justified limitations of anonymous inodes. Moving pidfds to a tiny
pseudo filesystem allows:
* statx() on pidfds becomes useful for the first time.
* pidfds can be compared simply via statx() and then comparing inode
numbers.
* pidfds have unique inode numbers for the system lifetime.
* struct pid is now stashed in inode->i_private instead of
file->private_data. This means it is now possible to introduce
concepts that operate on a process once all file descriptors have been
closed. A concrete example is kill-on-last-close.
* file->private_data is freed up for per-file options for pidfds.
* Each struct pid will refer to a different inode but the same struct
pid will refer to the same inode if it's opened multiple times. In
contrast to now where each struct pid refers to the same inode. Even
if we were to move to anon_inode_create_getfile() which creates new
inodes we'd still be associating the same struct pid with multiple
different inodes.
The tiny pseudo filesystem is not visible anywhere in userspace exactly
like e.g., pipefs and sockfs. There's no lookup, there's no complex
inode operations, nothing. Dentries and inodes are always deleted when
the last pidfd is closed.
We allocate a new inode for each struct pid and we reuse that inode for
all pidfds. We use iget_locked() to find that inode again based on the
inode number which isn't recycled. We allocate a new dentry for each
pidfd that uses the same inode. That is similar to anonymous inodes
which reuse the same inode for thousands of dentries. For pidfds we're
talking way less than that. There usually won't be a lot of concurrent
openers of the same struct pid. They can probably often be counted on
two hands. I know that systemd does use separate pidfd for the same
struct pid for various complex process tracking issues. So I think with
that things actually become way simpler. Especially because we don't
have to care about lookup. Dentries and inodes continue to be always
deleted.
The code is entirely optional and fairly small. If it's not selected we
fallback to anonymous inodes. Heavily inspired by nsfs which uses a
similar stashing mechanism just for namespaces.
Link: https://lore.kernel.org/r/20240213-vfs-pidfd_fs-v1-2-f863f58cfce1@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Boqun pointed out that workqueues aren't handling BH work items on offlined
CPUs. Unlike tasklet which transfers out the pending tasks from
CPUHP_SOFTIRQ_DEAD, BH workqueue would just leave them pending which is
problematic. Note that this behavior is specific to BH workqueues as the
non-BH per-CPU workers just become unbound when the CPU goes offline.
This patch fixes the issue by draining the pending BH work items from an
offlined CPU from CPUHP_SOFTIRQ_DEAD. Because work items carry more context,
it's not as easy to transfer the pending work items from one pool to
another. Instead, run BH work items which execute the offlined pools on an
online CPU.
Note that this assumes that no further BH work items will be queued on the
offlined CPUs. This assumption is shared with tasklet and should be fine for
conversions. However, this issue also exists for per-CPU workqueues which
will just keep executing work items queued after CPU offline on unbound
workers and workqueue should reject per-CPU and BH work items queued on
offline CPUs. This will be addressed separately later.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-and-reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Link: http://lkml.kernel.org/r/Zdvw0HdSXcU3JZ4g@boqun-archlinux
The update_cpumask(), checks for newly requested cpumask by calling
validate_change(), which returns an error on passing an invalid set
of cpu(s). Independent of the error returned, update_cpumask() always
returns zero, suppressing the error and returning success to the user
on writing an invalid cpu range for a cpuset. Fix it by returning
retval instead, which is returned by validate_change().
Fixes: 99fe36ba6f ("cgroup/cpuset: Improve temporary cpumasks handling")
Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Cc: stable@vger.kernel.org # v6.6+
Signed-off-by: Tejun Heo <tj@kernel.org>
We've removed the SLAB allocator, cpuset_do_slab_mem_spread() and
SLAB_MEM_SPREAD, memory_spread_slab is a no-op now. We can mark
memory_spread_slab as obsolete in case someone still wants to use it after
cpuset_do_slab_mem_spread() removed. For more details, please check [1].
[1] https://lore.kernel.org/lkml/32bc1403-49da-445a-8c00-9686a3b0d6a3@redhat.com/T/#m8e292e21b00f95a4bb8086371fa7387fa4ea8f60
tj: Description and cosmetic updates.
Signed-off-by: Xiongwei Song <xiongwei.song@windriver.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In configurations with CONFIG_TICK_ONESHOT but no CONFIG_NO_HZ or
CONFIG_HIGH_RES_TIMERS, tick_sched_timer_dying() is stubbed out,
but still defined as a global function as well:
kernel/time/tick-sched.c:1599:6: error: redefinition of 'tick_sched_timer_dying'
1599 | void tick_sched_timer_dying(int cpu)
| ^
kernel/time/tick-sched.h:111:20: note: previous definition is here
111 | static inline void tick_sched_timer_dying(int cpu) { }
| ^
This configuration only appears with ARM CONFIG_ARCH_BCM_MOBILE,
which should not actually select CONFIG_TICK_ONESHOT.
Adjust the #ifdef for the stub to match the condition for building the
tick-sched.c file for consistency with the definition and to avoid
the build regression.
Fixes: 3aedb7fcd8 ("tick/sched: Remove useless oneshot ifdeffery")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240228123850.3499024-1-arnd@kernel.org
Fix a possible memory leak in update_exclusive_cpumask() by moving the
alloc_cpumasks() down after the validate_change() check which can fail
and still before the temporary cpumasks are needed.
Fixes: e2ffe502ba ("cgroup/cpuset: Add cpuset.cpus.exclusive for v2")
Reported-and-tested-by: Mirsad Todorovac <mirsad.todorovac@alu.hr>
Closes: https://lore.kernel.org/lkml/14915689-27a3-4cd8-80d2-9c30d0c768b6@alu.unizg.hr
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # v6.7+
Move the pidfd file operations over to their own file in preparation of
implementing pidfs and to isolate them from other mostly unrelated
functionality in other files.
Link: https://lore.kernel.org/r/20240213-vfs-pidfd_fs-v1-1-f863f58cfce1@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
'days' is a s64 (from div_s64), and so should use a %lld specifier.
This was found by extending KUnit's assertion macros to use gcc's
__printf attribute.
Fixes: 2760105516 ("time: Improve performance of time64_to_tm()")
Signed-off-by: David Gow <davidgow@google.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
bringup_nonboot_cpus() gets passed the 'setup_max_cpus'
variable in init/main.c - which is also the name of the parameter,
shadowing the name.
To reduce confusion and to allow the 'setup_max_cpus' value
to be #defined in the <linux/smp.h> header, use the 'max_cpus'
name for the function parameter name.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
The next timer (re-)evaluation, with the purpose of entering/updating
the dyntick mode, can happen from 3 sites and none of them are relevant
while the CPU is offline:
1) The idle loop:
a) From the quick check helping the cpuidle governor to heuristically
predict the best C-state.
b) While stopping the tick.
But if the CPU is offline, the tick has been cancelled and there is
consequently no need to further stop the tick.
2) Remote expiry: when a CPU remotely expires global timers on behalf of
another CPU, the latter target's next timer is re-evaluated
afterwards. However remote expîry doesn't happen on offline CPUs.
3) IRQ exit: on nohz_full mode, the tick is (re-)evaluated on IRQ exit.
But full dynticks is disabled on offline CPUs.
Therefore it is safe to assume that no next dyntick timer lookup can
be performed on offline CPUs.
Assert this expectation to report any surprise.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-17-frederic@kernel.org
The timekeeping duty is handed over from the outgoing CPU on stop
machine, then the oneshot tick is stopped right after. Therefore it's
guaranteed that the current CPU isn't the timekeeper upon its last call
to idle.
Besides, calling tick_nohz_idle_stop_tick() while the dying CPU goes
into idle suggests that the tick is going to be stopped while it is
actually stopped already from the appropriate CPU hotplug state.
Remove the confusing call and the obsolete case handling and convert it
to a sanity check that verifies the above assumption.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-16-frederic@kernel.org
The timekeeping duty is handed over from the outgoing CPU within stop
machine. This works well if CONFIG_NO_HZ_COMMON=n or the tick is in
high-res mode. However in low-res dynticks mode, the tick isn't
cancelled until the clockevent is shut down, which can happen later. The
tick may therefore fire again once IRQs are re-enabled on stop machine
and until IRQs are disabled for good upon the last call to idle.
That's so many opportunities for a timekeeper to go idle and the
outgoing CPU to take over that duty. This is why
tick_nohz_idle_stop_tick() is called one last time on idle if the CPU
is seen offline: so that the timekeeping duty is handed over again in
case the CPU has re-taken the duty.
This means there are two timekeeping handovers on CPU down hotplug with
different undocumented constraints and purposes:
1) A handover on stop machine for !dynticks || highres. All online CPUs
are guaranteed to be non-idle and the timekeeping duty can be safely
handed-over. The hrtimer tick is cancelled so it is guaranteed that in
dynticks mode the outgoing CPU won't take again the duty.
2) A handover on last idle call for dynticks && lowres. Setting the
duty to TICK_DO_TIMER_NONE makes sure that a CPU will take over the
timekeeping.
Prepare for consolidating the handover to a single place (the first one)
with shutting down the low-res tick as well from
tick_cancel_sched_timer() as well. This will simplify the handover and
unify the tick cancellation between high-res and low-res.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-15-frederic@kernel.org
The nohz mode field tells about low resolution nohz mode or high
resolution nohz mode but it doesn't tell about high resolution non-nohz
mode.
In order to retrieve the latter state, tick_cancel_sched_timer() must
fiddle with struct hrtimer's internals to guess if the tick has been
initialized in high resolution.
Move instead the nohz mode field information into the tick flags and
provide two new bits: one to know if the tick is in nohz mode and
another one to know if the tick is in high resolution. The combination
of those two flags provides all the needed informations to determine
which of the three tick modes is running.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-14-frederic@kernel.org
The individual bitfields of struct tick_sched must be modified from
IRQs disabled places, otherwise local modifications can race due to them
sharing the same memory storage.
The recent move of the "got_idle_tick" bitfield to its own storage shows
that the use of these bitfields, as pretty as they look, can be as much
error prone.
In order to avoid future issues of the like and make sure that those
bitfields are safely accessed, move those flags to an explicit mask
along with a mutator function performing the basic IRQs disabled sanity
check.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-13-frederic@kernel.org
tick_nohz_idle_got_tick() is called by cpuidle_reflect() within the idle
loop with interrupts enabled. This function modifies the struct
tick_sched's bitfield "got_idle_tick". However this bitfield is stored
within the same mask as other bitfields that can be modified from
interrupts.
Fortunately so far it looks like the only race that can happen is while
writing ->got_idle_tick to 0, an interrupt fires and writes the
->idle_active field to 0. It's then possible that the interrupted write
to ->got_idle_tick writes back the old value of ->idle_active back to 1.
However if that happens, the worst possible outcome is that the time
spent between that interrupt and the upcoming call to
tick_nohz_idle_exit() is accounted as idle, which is negligible quantity.
Still all the bitfield writes within this struct tick_sched's shadow
mask should be IRQ-safe. Therefore move this bitfield out to its own
storage to avoid further suprises.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-12-frederic@kernel.org
The full-nohz update function checks if the nohz mode is active before
proceeding. It considers one exception though: if the tick is already
stopped even though the nohz mode is inactive, it still moves on in
order to update/restart the tick if needed.
However in order for the tick to be stopped, the nohz_mode has to be
either NOHZ_MODE_LOWRES or NOHZ_MODE_HIGHRES. Therefore it doesn't make
sense to test if the tick is stopped before verifying NOHZ_MODE_INACTIVE
mode.
Remove the needless related condition.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-11-frederic@kernel.org
The broadcast shutdown code is executed through a random explicit call
within stop machine from the outgoing CPU.
However the tick broadcast is a midware between the tick callback and
the clocksource, therefore it makes more sense to shut it down after the
tick callback and before the clocksource drivers.
Move it instead to the common tick shutdown CPU hotplug state where
related operations can be ordered from highest to lowest level.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-10-frederic@kernel.org
The tick hrtimer is cancelled right before hrtimers are migrated. This
is done from the hrtimer subsystem even though it shouldn't know about
its actual users.
Move instead the tick hrtimer cancellation to the relevant CPU hotplug
state that aims at centralizing high level tick shutdown operations so
that the related flow is easy to follow.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-9-frederic@kernel.org
During the CPU offlining process, the various timer tick features are
shut down from scattered places, sometimes from teardown callbacks on
stop machine, sometimes through explicit calls, sometimes from the
control CPU after the CPU died. The reason why these shutdown operations
are spread around is not always clear and it makes the tick lifecycle
hard to follow.
The tick should be shut down in order from highest to lowest level:
On stop machine from the dying CPU (high-level):
1) Hand-over the timekeeping duty (tick_handover_do_timer())
2) Cancel the tick implementation called by the clockevent callback
(tick_cancel_sched_timer())
3) Shutdown broadcasting (tick_offline_cpu() / tick_broadcast_offline())
On stop machine from the dying CPU (low-level):
4) Shutdown clockevents drivers (CPUHP_AP_*_TIMER_STARTING states)
From the control CPU after the CPU died (low-level):
5) Shutdown/unregister/cleanup clockevents for the dead CPU
(tick_cleanup_dead_cpu())
Instead the current order is 2, 4 (both from CPU hotplug states), then
1 and 3 through direct calls. This layout and order don't make much
sense. The operations 1, 2, 3 should be gathered together and in order.
Sort this situation with creating a new TICK shut-down CPU hotplug state
and start with introducing the timekeeping duty hand-over there. The
state must precede hrtimers migration because the tick hrtimer will be
stopped from it in a further patch.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-8-frederic@kernel.org
The tick sched structure is already cleared from tick_cancel_sched_timer(),
so there is no need to clear that field again.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240225225508.11587-7-frederic@kernel.org
Linus Torvalds