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sched/core: Avoid _cond_resched() for PREEMPT=y 

On fully preemptible kernels _cond_resched() is pointless, so avoid
emitting any code for it.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2016-09-19 12:57:53 +02:00 committed by Ingo Molnar
parent 9af6528ee9
commit 35a773a079
2 changed files with 6 additions and 0 deletions
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4
include/linux/sched.h
View File

@ -3209,7 +3209,11 @@ static inline int signal_pending_state(long state, struct task_struct *p)
* cond_resched_lock() will drop the spinlock before scheduling,
* cond_resched_softirq() will enable bhs before scheduling.
*/
#ifndef CONFIG_PREEMPT
extern int _cond_resched(void);
#else
static inline int _cond_resched(void) { return 0; }
#endif
#define cond_resched() ({ \
___might_sleep(__FILE__, __LINE__, 0); \

2
kernel/sched/core.c
View File

@ -4883,6 +4883,7 @@ SYSCALL_DEFINE0(sched_yield)
return 0;
}
#ifndef CONFIG_PREEMPT
int __sched _cond_resched(void)
{
if (should_resched(0)) {
@ -4892,6 +4893,7 @@ int __sched _cond_resched(void)
return 0;
}
EXPORT_SYMBOL(_cond_resched);
#endif
/*
* __cond_resched_lock() - if a reschedule is pending, drop the given lock,