Re: [RFC PATCH] freezer: revert 27920651fe "PM / Freezer: Makefake_signal_wake_up() wake TASK_KILLABLE tasks too"

[Tejun Heo]

Hey, again.

On Mon, Oct 31, 2011 at 04:30:59PM -0700, Tejun Heo wrote:
> I can't remember one off the top of my head but I'm pretty sure there
> at least are few which expect tight inter-locking between sleeps and
> wakeups.  I'll look for examples and post reply.  ISTR them being
> kernel threads so this might not apply directly but it's still a
> dangerous game to play.

Hmm... I couldn't find KILLABLE used like that but here are two
UNINTERRUPTIBLE sleep examples.

* kthread_start() depends on the fact that a kthread won't be woken up
  from UNINTERRUPTIBLE sleep spuriously.

* jfs_flush_journal() doesn't check whether the wakeup was spurious
  after waiting if !tblkGC_COMMITTED.

Maybe we can re-define KILLABLE as killable && freezable but IMHO that
requires pretty strong rationales.  If at all possible, let's not
diddle with that if it can be worked around some other way.

Thank you.

-- 
tejun
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