On 2018-03-07 09:45:29 [-0600], Corey Minyard wrote: > > I have no idea what is the wisest thing to do here. The obvious fix > > would be to use the irqsafe() variant here and not drop the lock between > > wake ups. That is essentially what swake_up_all_locked() does which I > > need for the completions (and based on some testing most users have one > > waiter except during PM and some crypto code). > > It is probably no comparison to wake_up_q() (which does multiple wake > > ups without a context switch) but then we did this before like that. > > > > Preferably we would have a proper list_splice() and some magic in the > > "early" dequeue part that works. > > > > Maybe just modify the block code to run the swake_up_all() call in a > workqueue > or tasklet? If you think that works, I'll create a patch, test it, and > submit it if > all goes well. It will work but I don't think pushing this into workqueue/tasklet is a good idea. You want to wakeup all waiters on waitqueue X (probably one waiter) and instead there is one one wakeup + ctx-switch which does the final wakeup. But now I had an idea: swake_up_all() could iterate over list and instead performing wakes it would just wake_q_add() the tasks. Drop the lock and then wake_up_q(). So in case there is wakeup pending and the task removed itself from the list then the task may observe a spurious wakeup. > Thanks, > > -corey Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
