Commit 02b67cc3 authored by Herbert Xu's avatar Herbert Xu Committed by Ingo Molnar
Browse files

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: default avatarIngo Molnar <mingo@elte.hu>
parent 03319ec8

include/linux/kernel.h

+2 −2
Original line number Diff line number Diff line
@@ -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

include/linux/sched.h

+12 −1
Original line number Diff line number Diff line
@@ -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);

kernel/sched.c

+4 −2
Original line number Diff line number Diff line
@@ -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,