[PATCH 1/2] sched: Drop the need_resched() loop from cond_resched()

Frederic Weisbecker
2009-07-10T14:50:10Z

The schedule() function is a loop that reschedules the current task
while the TIF_NEED_RESCHED flag is set:

void schedule(void)
{
need_resched:
/* schedule code */
if (need_resched())
goto need_resched;
}

And cond_resched() repeat this loop:

do {
add_preempt_count(PREEMPT_ACTIVE);
schedule();
sub_preempt_count(PREEMPT_ACTIVE);
} while(need_resched());

This loop is needless because schedule() already did the check and
nothing can set TIF_NEED_RESCHED between schedule() exit and the loop
check in need_resched().

Then remove this needless loop.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/sched.c | 8 +++-----
1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 4d1e387..87ecac1 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6613,11 +6613,9 @@ static void __cond_resched(void)
* PREEMPT_ACTIVE, which could trigger a second
* cond_resched() call.
*/
- do {
- add_preempt_count(PREEMPT_ACTIVE);
- schedule();
- sub_preempt_count(PREEMPT_ACTIVE);
- } while (need_resched());
+ add_preempt_count(PREEMPT_ACTIVE);
+ schedule();
+ sub_preempt_count(PREEMPT_ACTIVE);
}

int __sched _cond_resched(void)
--
1.6.2.3