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Add new 'cond_resched_bkl()' helper function 

It acts exactly like a regular 'cond_resched()', but will not get
optimized away when CONFIG_PREEMPT is set.

Normal kernel code is already preemptable in the presense of
CONFIG_PREEMPT, so cond_resched() is optimized away (see commit
02b67cc3ba "sched: do not do
cond_resched() when CONFIG_PREEMPT").

But when wanting to conditionally reschedule while holding a lock, you
need to use "cond_sched_lock(lock)", and the new function is the BKL
equivalent of that.

Also make fs/locks.c use it.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2008-05-11 16:04:48 -07:00
parent 9662369786
commit c3921ab715
3 changed files with 6 additions and 4 deletions
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2
fs/locks.c
View File

@ -773,7 +773,7 @@ static int flock_lock_file(struct file *filp, struct file_lock *request)
* give it the opportunity to lock the file. * give it the opportunity to lock the file.
*/ */
if (found) if (found)
cond_resched(); cond_resched_bkl();
find_conflict: find_conflict:
for_each_lock(inode, before) { for_each_lock(inode, before) {

6
include/linux/sched.h
View File

@ -2037,13 +2037,13 @@ static inline int need_resched(void)
* cond_resched_lock() will drop the spinlock before scheduling, * cond_resched_lock() will drop the spinlock before scheduling,
* cond_resched_softirq() will enable bhs before scheduling. * cond_resched_softirq() will enable bhs before scheduling.
*/ */
extern int _cond_resched(void);
#ifdef CONFIG_PREEMPT #ifdef CONFIG_PREEMPT
static inline int cond_resched(void) static inline int cond_resched(void)
{ {
return 0; return 0;
} }
#else #else
extern int _cond_resched(void);
static inline int cond_resched(void) static inline int cond_resched(void)
{ {
return _cond_resched(); return _cond_resched();
@ -2051,6 +2051,10 @@ static inline int cond_resched(void)
#endif #endif
extern int cond_resched_lock(spinlock_t * lock); extern int cond_resched_lock(spinlock_t * lock);
extern int cond_resched_softirq(void); extern int cond_resched_softirq(void);
static inline int cond_resched_bkl(void)
{
return _cond_resched();
}
/* /*
* Does a critical section need to be broken due to another * Does a critical section need to be broken due to another

2
kernel/sched.c
View File

@ -5525,7 +5525,6 @@ static void __cond_resched(void)
} while (need_resched()); } while (need_resched());
} }
#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PREEMPT_VOLUNTARY)
int __sched _cond_resched(void) int __sched _cond_resched(void)
{ {
if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) && if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) &&
@ -5536,7 +5535,6 @@ int __sched _cond_resched(void)
return 0; return 0;
} }
EXPORT_SYMBOL(_cond_resched); EXPORT_SYMBOL(_cond_resched);
#endif
/* /*
* cond_resched_lock() - if a reschedule is pending, drop the given lock, * cond_resched_lock() - if a reschedule is pending, drop the given lock,