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x86/preempt: Move preempt count to percpu hot section 

No functional change.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-4-brgerst@gmail.com
pull/1183/head
Brian Gerst 2025-03-03 11:52:38 -05:00 committed by Ingo Molnar
parent 972f9cdff9
commit 46e8fff6d4
4 changed files with 17 additions and 14 deletions
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1
arch/x86/include/asm/current.h
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@ -14,7 +14,6 @@ struct task_struct;
struct pcpu_hot {
struct task_struct *current_task;
int preempt_count;
int cpu_number;
#ifdef CONFIG_MITIGATION_CALL_DEPTH_TRACKING
u64 call_depth;

25
arch/x86/include/asm/preempt.h
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@ -4,10 +4,11 @@
#include <asm/rmwcc.h>
#include <asm/percpu.h>
#include <asm/current.h>
#include <linux/static_call_types.h>
DECLARE_PER_CPU_CACHE_HOT(int, __preempt_count);
/* We use the MSB mostly because its available */
#define PREEMPT_NEED_RESCHED 0x80000000
@ -23,18 +24,18 @@
*/
static __always_inline int preempt_count(void)
{
return raw_cpu_read_4(pcpu_hot.preempt_count) & ~PREEMPT_NEED_RESCHED;
return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
}
static __always_inline void preempt_count_set(int pc)
{
int old, new;
old = raw_cpu_read_4(pcpu_hot.preempt_count);
old = raw_cpu_read_4(__preempt_count);
do {
new = (old & PREEMPT_NEED_RESCHED) |
(pc & ~PREEMPT_NEED_RESCHED);
} while (!raw_cpu_try_cmpxchg_4(pcpu_hot.preempt_count, &old, new));
} while (!raw_cpu_try_cmpxchg_4(__preempt_count, &old, new));
}
/*
@ -43,7 +44,7 @@ static __always_inline void preempt_count_set(int pc)
#define init_task_preempt_count(p) do { } while (0)
#define init_idle_preempt_count(p, cpu) do { \
per_cpu(pcpu_hot.preempt_count, (cpu)) = PREEMPT_DISABLED; \
per_cpu(__preempt_count, (cpu)) = PREEMPT_DISABLED; \
} while (0)
/*
@ -57,17 +58,17 @@ static __always_inline void preempt_count_set(int pc)
static __always_inline void set_preempt_need_resched(void)
{
raw_cpu_and_4(pcpu_hot.preempt_count, ~PREEMPT_NEED_RESCHED);
raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
}
static __always_inline void clear_preempt_need_resched(void)
{
raw_cpu_or_4(pcpu_hot.preempt_count, PREEMPT_NEED_RESCHED);
raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
}
static __always_inline bool test_preempt_need_resched(void)
{
return !(raw_cpu_read_4(pcpu_hot.preempt_count) & PREEMPT_NEED_RESCHED);
return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
}
/*
@ -76,12 +77,12 @@ static __always_inline bool test_preempt_need_resched(void)
static __always_inline void __preempt_count_add(int val)
{
raw_cpu_add_4(pcpu_hot.preempt_count, val);
raw_cpu_add_4(__preempt_count, val);
}
static __always_inline void __preempt_count_sub(int val)
{
raw_cpu_add_4(pcpu_hot.preempt_count, -val);
raw_cpu_add_4(__preempt_count, -val);
}
/*
@ -91,7 +92,7 @@ static __always_inline void __preempt_count_sub(int val)
*/
static __always_inline bool __preempt_count_dec_and_test(void)
{
return GEN_UNARY_RMWcc("decl", __my_cpu_var(pcpu_hot.preempt_count), e,
return GEN_UNARY_RMWcc("decl", __my_cpu_var(__preempt_count), e,
__percpu_arg([var]));
}
@ -100,7 +101,7 @@ static __always_inline bool __preempt_count_dec_and_test(void)
*/
static __always_inline bool should_resched(int preempt_offset)
{
return unlikely(raw_cpu_read_4(pcpu_hot.preempt_count) == preempt_offset);
return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
}
#ifdef CONFIG_PREEMPTION

4
arch/x86/kernel/cpu/common.c
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@ -2066,12 +2066,14 @@ __setup("setcpuid=", setup_setcpuid);
DEFINE_PER_CPU_CACHE_HOT(struct pcpu_hot, pcpu_hot) = {
.current_task = &init_task,
.preempt_count = INIT_PREEMPT_COUNT,
.top_of_stack = TOP_OF_INIT_STACK,
};
EXPORT_PER_CPU_SYMBOL(pcpu_hot);
EXPORT_PER_CPU_SYMBOL(const_pcpu_hot);
DEFINE_PER_CPU_CACHE_HOT(int, __preempt_count) = INIT_PREEMPT_COUNT;
EXPORT_PER_CPU_SYMBOL(__preempt_count);
#ifdef CONFIG_X86_64
static void wrmsrl_cstar(unsigned long val)
{

1
include/linux/preempt.h
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@ -319,6 +319,7 @@ do { \
#ifdef CONFIG_PREEMPT_NOTIFIERS
struct preempt_notifier;
struct task_struct;
/**
* preempt_ops - notifiers called when a task is preempted and rescheduled