On Fri, May 15, 2015 at 9:04 AM, Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > > To fix it I added this along a comment: Ok, this looks good as a explanation/fix for the races (and also as an example of my worry about waitqueue_active() use in general). However, it now makes me suspect that the optimistic "let's check if they are even active" may not be worth it any more. You're adding a "smp_mb()" in order to avoid taking the real lock. Although I guess there are two locks there (one for each wait-queue) so maybe it's worth it. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html