> wait_event:
>
> prepare_to_wait(wq) // takes wq->lock
>
> if (!CONDITION)
> schedule();
>
> Now,
>
> CONDITION = 1;
> wake_up(wq);
>
> at least need the full mb() before lits_empty().
You're right, but it would probably only matter for inlining
wait_event:
prepare_to_wait(wq) // takes wq-lock
if (!CONDITION)
schedule();
Now,
CONDITION = 1;
wake_up(wq);
at least need the full mb() before lits_empty().
You're right, but it would probably only matter for inlining with LTO
(if the
On 10/09, Peter Zijlstra wrote:
>
> One thing you might need to consider is the memory ordering, will the
> list_empty -- either careful or not -- observe the right list pointer,
> or could it -- when racing with wait_event()/prepare_to_wait() --
> observe a stale value. Or.. is that all already
On Tue, 2012-10-09 at 06:37 -0700, Andi Kleen wrote:
> Ivo Sieben writes:
>
> > Check the waitqueue task list to be non empty before entering the critical
> > section. This prevents locking the spin lock needlessly in case the queue
> > was empty, and therefor also prevent scheduling overhead on
Ivo Sieben writes:
> Check the waitqueue task list to be non empty before entering the critical
> section. This prevents locking the spin lock needlessly in case the queue
> was empty, and therefor also prevent scheduling overhead on a PREEMPT_RT
> system.
>
> Signed-off-by: Ivo Sieben
> ---
>
Check the waitqueue task list to be non empty before entering the critical
section. This prevents locking the spin lock needlessly in case the queue
was empty, and therefor also prevent scheduling overhead on a PREEMPT_RT
system.
Signed-off-by: Ivo Sieben
---
REPOST:
Request for comments:
-
Check the waitqueue task list to be non empty before entering the critical
section. This prevents locking the spin lock needlessly in case the queue
was empty, and therefor also prevent scheduling overhead on a PREEMPT_RT
system.
Signed-off-by: Ivo Sieben meltedpiano...@gmail.com
---
REPOST:
Ivo Sieben meltedpiano...@gmail.com writes:
Check the waitqueue task list to be non empty before entering the critical
section. This prevents locking the spin lock needlessly in case the queue
was empty, and therefor also prevent scheduling overhead on a PREEMPT_RT
system.
Signed-off-by:
On Tue, 2012-10-09 at 06:37 -0700, Andi Kleen wrote:
Ivo Sieben meltedpiano...@gmail.com writes:
Check the waitqueue task list to be non empty before entering the critical
section. This prevents locking the spin lock needlessly in case the queue
was empty, and therefor also prevent
On 10/09, Peter Zijlstra wrote:
One thing you might need to consider is the memory ordering, will the
list_empty -- either careful or not -- observe the right list pointer,
or could it -- when racing with wait_event()/prepare_to_wait() --
observe a stale value. Or.. is that all already
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