Disable preemption from the last caller of __schedule() that needed to
carry this duty. This way we can remove this responsability from
__scheduler() so to optimize the preempt_count() operations to
a single place on preempt_schedule*() functions.
Suggested-by: Linus Torvalds <torva...@linux-foundation.org>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
---
kernel/sched/core.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 182127a..b23def2 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2723,9 +2723,7 @@ again:
* - return from syscall or exception to user-space
* - return from interrupt-handler to user-space
*
- * WARNING: all callers must re-check need_resched() afterward and reschedule
- * accordingly in case an event triggered the need for rescheduling (such as
- * an interrupt waking up a task) while preemption was disabled in
__schedule().
+ * WARNING: must be called with preemption disabled!
*/
static void __sched __schedule(void)
{
@@ -2734,7 +2732,6 @@ static void __sched __schedule(void)
struct rq *rq;
int cpu;
- preempt_disable();
cpu = smp_processor_id();
rq = cpu_rq(cpu);
rcu_note_context_switch();
@@ -2798,8 +2795,6 @@ static void __sched __schedule(void)
raw_spin_unlock_irq(&rq->lock);
post_schedule(rq);
-
- sched_preempt_enable_no_resched();
}
static inline void sched_submit_work(struct task_struct *tsk)
@@ -2820,7 +2815,9 @@ asmlinkage __visible void __sched schedule(void)
sched_submit_work(tsk);
do {
+ preempt_disable();
__schedule();
+ sched_preempt_enable_no_resched();
} while (need_resched());
}
EXPORT_SYMBOL(schedule);
--
2.1.4
--
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