On Sun, 24 Feb 2008, Pavel Machek wrote: > > > What locking protects this variable? What happens when suspending_task > > > exits? (Hmm, that would probably be bug, anyway?) > > > > It's protected by whatever existing locking scheme allows only one > > task to start a system sleep at a time. For example, the suspending > > task has to get a write lock on pm_sleep_rwsem. > > And readers of suspending_task are protected by? I added a comment about that too. > At the very least, you'd need rmb() before reading it and wmb() after > writing to it, but I'm not sure if that's enough on every obscure > architecture out there. No, neither one is needed because of the way suspending_task is used. It's not necessary for a reader R to see the variable's actual value; all R needs to know is whether or not suspending_task is equal to R. Since the only process which can set suspending_task to R is R itself, and since R will set suspending_task back to NULL before releasing the write lock on pm_sleep_rwsem, there's never any ambiguity. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
