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sched/core, sched/x86: Kill thread_info::saved_preempt_count

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With the introduction of the context switch preempt_count invariant,
and the demise of PREEMPT_ACTIVE, its pointless to save/restore the
per-cpu preemption count, it must always be 2.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-09-28 18:11:18 +02:00 committed by Ingo Molnar
parent da7142e2ed
commit d87b7a3379
4 changed files with 1 additions and 22 deletions
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5
arch/x86/include/asm/preempt.h
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@ -30,12 +30,9 @@ static __always_inline void preempt_count_set(int pc)
/*
* must be macros to avoid header recursion hell
*/
#define init_task_preempt_count(p) do { \
task_thread_info(p)->saved_preempt_count = FORK_PREEMPT_COUNT; \
} while (0)
#define init_task_preempt_count(p) do { } while (0)
#define init_idle_preempt_count(p, cpu) do { \
task_thread_info(p)->saved_preempt_count = PREEMPT_ENABLED; \
per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
} while (0)

2
arch/x86/include/asm/thread_info.h
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@ -57,7 +57,6 @@ struct thread_info {
__u32 flags; /* low level flags */
__u32 status; /* thread synchronous flags */
__u32 cpu; /* current CPU */
int saved_preempt_count;
mm_segment_t addr_limit;
void __user *sysenter_return;
unsigned int sig_on_uaccess_error:1;
@ -69,7 +68,6 @@ struct thread_info {
.task = &tsk, \
.flags = 0, \
.cpu = 0, \
.saved_preempt_count = INIT_PREEMPT_COUNT, \
.addr_limit = KERNEL_DS, \
}

8
arch/x86/kernel/process_32.c
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@ -279,14 +279,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
set_iopl_mask(next->iopl);
/*
* If it were not for PREEMPT_ACTIVE we could guarantee that the
* preempt_count of all tasks was equal here and this would not be
* needed.
*/
task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);
this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);
/*
* Now maybe handle debug registers and/or IO bitmaps
*/

8
arch/x86/kernel/process_64.c
View File

@ -401,14 +401,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
*/
this_cpu_write(current_task, next_p);
/*
* If it were not for PREEMPT_ACTIVE we could guarantee that the
* preempt_count of all tasks was equal here and this would not be
* needed.
*/
task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);
this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);
/* Reload esp0 and ss1. This changes current_thread_info(). */
load_sp0(tss, next);