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sched: do not do cond_resched() when CONFIG_PREEMPT 

Why do we even have cond_resched when real preemption
is on? It seems to be a waste of space and time.

remove cond_resched with CONFIG_PREEMPT on.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Herbert Xu 2008-01-25 21:08:28 +01:00 committed by Ingo Molnar
parent 03319ec8b0
commit 02b67cc3ba
3 changed files with 18 additions and 5 deletions
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4
include/linux/kernel.h
View File

@ -105,8 +105,8 @@ struct user;
* supposed to.
*/
#ifdef CONFIG_PREEMPT_VOLUNTARY
extern int cond_resched(void);
# define might_resched() cond_resched()
extern int _cond_resched(void);
# define might_resched() _cond_resched()
#else
# define might_resched() do { } while (0)
#endif

13
include/linux/sched.h
View File

@ -1885,7 +1885,18 @@ static inline int need_resched(void)
* cond_resched_lock() will drop the spinlock before scheduling,
* cond_resched_softirq() will enable bhs before scheduling.
*/
extern int cond_resched(void);
#ifdef CONFIG_PREEMPT
static inline int cond_resched(void)
{
return 0;
}
#else
extern int _cond_resched(void);
static inline int cond_resched(void)
{
return _cond_resched();
}
#endif
extern int cond_resched_lock(spinlock_t * lock);
extern int cond_resched_softirq(void);

6
kernel/sched.c
View File

@ -4678,7 +4678,8 @@ static void __cond_resched(void)
} while (need_resched());
}
int __sched cond_resched(void)
#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PREEMPT_VOLUNTARY)
int __sched _cond_resched(void)
{
if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) &&
system_state == SYSTEM_RUNNING) {
@ -4687,7 +4688,8 @@ int __sched cond_resched(void)
}
return 0;
}
EXPORT_SYMBOL(cond_resched);
EXPORT_SYMBOL(_cond_resched);
#endif
/*
* cond_resched_lock() - if a reschedule is pending, drop the given lock,