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 covered in on the use
> site.
I agree.
Without spin_lock(q->lock) (or some other barriers) wait_event-like
code can miss an event.
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().
Oleg.
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