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Miquel Raynal b5efb4e6fb can: sja1000: Always restart the Tx queue after an overrun 
Upstream commit 717c6ec241 ("can: sja1000: Prevent overrun stalls with
a soft reset on Renesas SoCs") fixes an issue with Renesas own SJA1000
CAN controller reception: the Rx buffer is only 5 messages long, so when
the bus loaded (eg. a message every 50us), overrun may easily
happen. Upon an overrun situation, due to a possible internal crosstalk
situation, the controller enters a frozen state which only can be
unlocked with a soft reset (experimentally). The solution was to offload
a call to sja1000_start() in a threaded handler. This needs to happen in
process context as this operation requires to sleep. sja1000_start()
basically enters "reset mode", performs a proper software reset and
returns back into "normal mode".

Since this fix was introduced, we no longer observe any stalls in
reception. However it was sporadically observed that the transmit path
would now freeze. Further investigation blamed the fix mentioned above,
and especially the reset operation. Reproducing the reset in a loop
helped identifying what could possibly go wrong. The sja1000 is a single
Tx queue device, which leverages the netdev helpers to process one Tx
message at a time. The logic is: the queue is stopped, the message sent
to the transceiver, once properly transmitted the controller sets a
status bit which triggers an interrupt, in the interrupt handler the
transmission status is checked and the queue woken up. Unfortunately, if
an overrun happens, we might perform the soft reset precisely between
the transmission of the buffer to the transceiver and the advent of the
transmission status bit. We would then stop the transmission operation
without re-enabling the queue, leading to all further transmissions to
be ignored.

The reset interrupt can only happen while the device is "open", and
after a reset we anyway want to resume normal operations, no matter if a
packet to transmit got dropped in the process, so we shall wake up the
queue. Restarting the device and waking-up the queue is exactly what
sja1000_set_mode(CAN_MODE_START) does. In order to be consistent about
the queue state, we must acquire a lock both in the reset handler and in
the transmit path to ensure serialization of both operations. It turns
out, a lock is already held when entering the transmit path, so we can
just acquire/release it as well with the regular net helpers inside the
threaded interrupt handler and this way we should be safe. As the
reset handler might still be called after the transmission of a frame to
the transceiver but before it actually gets transmitted, we must ensure
we don't leak the skb, so we free it (the behavior is consistent, no
matter if there was an skb on the stack or not).

Fixes: 717c6ec241 ("can: sja1000: Prevent overrun stalls with a soft reset on Renesas SoCs")
Cc: stable@vger.kernel.org
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/all/20231002160206.190953-1-miquel.raynal@bootlin.com
[mkl: fixed call to can_free_echo_skb()]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
 		2023-10-06 12:54:33 +02:00
Documentation Networking fixes for 6.6-rc2, including fixes from netfilter and bpf 2023-09-21 11:28:16 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
arch bpf-for-netdev 2023-10-04 08:28:07 -07:00
block blk-mq: fix tags UAF when shrinking q->nr_hw_queues 2023-09-11 16:17:34 -06:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto This update includes the following changes: 2023-08-29 11:23:29 -07:00
drivers can: sja1000: Always restart the Tx queue after an overrun 2023-10-06 12:54:33 +02:00
fs v6.6-rc3.vfs.ctime.revert 2023-09-21 10:15:26 -07:00
include tcp: fix quick-ack counting to count actual ACKs of new data 2023-10-04 15:34:18 -07:00
init workqueue: Changes for v6.6 2023-09-01 16:06:32 -07:00
io_uring io_uring/net: fix iter retargeting for selected buf 2023-09-14 10:12:55 -06:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel bpf-for-netdev 2023-10-04 08:28:07 -07:00
lib linux-kselftest-kunit-6.6-rc2 2023-09-12 09:05:49 -07:00
mm Revert "tmpfs: add support for multigrain timestamps" 2023-09-20 18:05:30 +02:00
net can: isotp: isotp_sendmsg(): fix TX state detection and wait behavior 2023-10-06 12:54:33 +02:00
rust Documentation work keeps chugging along; stuff for 6.6 includes: 2023-08-30 20:05:42 -07:00
samples VFIO updates for v6.6-rc1 2023-08-30 20:36:01 -07:00
scripts Kbuild fixes for v6.6 2023-09-16 15:27:00 -07:00
security selinux: fix handling of empty opts in selinux_fs_context_submount() 2023-09-12 17:31:08 -04:00
sound ASoC: Fixes for v6.6 2023-09-20 15:02:16 +02:00
tools netfilter pull request 2023-10-04 2023-10-04 14:53:17 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
…
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap for-linus-2023083101 2023-09-01 12:31:44 -07:00
.rustfmt.toml rust: add `.rustfmt.toml` 2022-09-28 09:02:20 +02:00
COPYING
…
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
…
MAINTAINERS Quite a collection of fixes this time, really too many 2023-10-04 11:30:22 -07:00
Makefile Linux 6.6-rc2 2023-09-17 14:40:24 -07:00
README
…

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.