Hi. On Thu, 2005-04-07 at 07:35, Rafael J. Wysocki wrote: > On Wednesday, 6 of April 2005 23:17, Pavel Machek wrote: > > > > > I don't think Rafael is suggesting ignoring them. He's suggesting what > > > > > I'm already doing: > > > > > - Signal so they enter the freezer if they leave the state; > > > > > - Don't count them when deciding whether freezing failed; > > > > > - Handle the case where they don't leave the state until post resume (I > > > > > let them enter the refrigerator, but have code in there to check whether > > > > > the freezer is still on). > > > > > > > > > > In this way, I handle kseriod and anything else uninterruptible without > > > > > any problems. > > > > > > > > What happens if a process owns a lock needed to suspend a device and it is > > > > waiting in TASK_UNINTERRUPTIBLE? > > > > > > Well, we're in trouble. :-) > > > > > > However, if any process that we have frozen owns such a lock, we're in trouble > > > too. > > > > No, we are not. Processes can't own any locks when they are in > > refrigerator... It is not ok to call refrigerator from any context > > where you own a lock. > > I didn't mean a lock in general, but a lock that is needed to suspend a device. > If a process holding that lock is frozen, the _suspend() routine for the device > won't complete, because it won't be able to get the lock. IOW it will go to > sleep and we are single-threaded at that time ... Or am I missing anything? Whenever this topic comes up, the discussion is always abstract. If someone could think of a lock that might actually deadlock suspending, we look seriously at the issue. In the meantime, all I can say, from roughly three years of developing and testing, is that it never seems to happen. And yes, I know that doesn't necessarily mean it can't. Perhaps it helps to remember that we're using bdev_io routines. All of the filesystem locking is completely out of the picture. Furthermore, we flush (well Suspend2 does) all pending I/O before freezing kernel threads. Regards, Nigel -- Nigel Cunningham Software Engineer, Canberra, Australia http://www.cyclades.com Bus: +61 (2) 6291 9554; Hme: +61 (2) 6292 8028; Mob: +61 (417) 100 574 Maintainer of Suspend2 Kernel Patches http://suspend2.net
