On Sat, 27 Jun 2009, Rafael J. Wysocki wrote: > > Speaking of races, have you noticed that the way power.work_done gets > > used is racy? > > Not really. :-) > > > You can't wait for the completion before releasing the > > lock, but then anything could happen. > > > > A safer approach would be to use a wait_queue. > > I'm not sure what you mean exactly. What's the race? Somebody calls pm_runtime_suspend when a suspend is already in progress. The routine sees that the status is RPM_SUSPENDING, so it prepares to wait until the suspend is finished. It drops the lock and calls wait_for_completion. But in between those last two steps, the suspend could finish and a resume could start up. Then the wait_for_completion wouldn't return until the device was fully resumed! Now I admit this isn't as bad as it sounds. The same sort of thing could happen even if there weren't two suspends going on at the same time; a resume could occur between when the routine drops the lock and when it returns. So okay, forget I mentioned it. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
