Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [RFC][PATCH -mm] Freezer: Handle uninterruptible tasks | Date | Sat, 7 Jul 2007 22:44:45 +0200 |
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On Saturday, 7 July 2007 13:31, Pavel Machek wrote: > Hi! > > > > I don't think we can do that. I suspect rename looks like: > > > > > > write directory entry in source > > > A) (uninterruptible wait for write) > > > write directory entry in destination > > > (uninterruptible wait for write) > > > write something else > > > > > > If we freeze some task in place "A)", we'll write to the disk when the > > > directory write is finished :-(. > > > > Renaming is a single syscall, so won't the process get frozen when the syscall > > finishes? > > It would be frozen when syscall finishes. But if we freeze it at A) > point, we have a problem.
With this patch, we don't freeze it. :-)
We do something like "send a freeze request to this task, but don't care if it doesn't freeze".
Now, IMHO, the correctness here is the question of for how long a task can be in TASK_UNINTERRUPTIBLE it it's not stuck (eg. the resource needed is gone indefinitely, like in NFS) and I think that's not very long.
For example, if the tasks sleeps on a mutex, then it waits for another task to release the mutex (interrupt handlers don't use mutexes) and I don't know of any realistic scenario in which it can last in that state throughout freeze_processes().
Greetings, Rafael
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