[lkml]   [2007]   [Jul]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC][PATCH -mm] Freezer: Handle uninterruptible tasks
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


"Premature optimization is the root of all evil." - Donald Knuth
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2007-07-07 22:41    [W:0.048 / U:53.928 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site