[lkml]   [2011]   [Nov]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC PATCH] freezer: revert 27920651fe "PM / Freezer: Make fake_signal_wake_up() wake TASK_KILLABLE tasks too"

On Tue, Nov 01, 2011 at 07:13:29PM +0100, Oleg Nesterov wrote:
> On 11/01, Tejun Heo wrote:
> >
> > Yeah yeah, Trond already pointed it out. I forgot about the
> > sigpending special case in schedule(), which I think is rather odd,
> I disagree with "rather odd" ;)
> We have a lot of examples of
> current->state = TASK_INTERRUPTIBLE;
> ...
> if (signal_pending())
> break;
> schedule();
> Without that special case in schedule() the code above becomes racy.
> Just consider __wait_event_interruptible().

But __wait_event_interruptible() does proper set-TASK_*, check
sigpending and schedule() sequence. As long as the waker performs
seg-sigpending, wakeup sequence in the correct order, nothing is
broken (as w/ any other wakeup conditions). The special case deals
with callers which don't check sigpending between set-TASK_* and
schedule() and that's the part I think is a bit odd. Whether I feel
odd or not is irrelevant tho - it's already there.

> > Any better ideas?
> Well. As a simple (probably temporary) fix, I'd suggest
> #define wait_event_freezekillable(wq, condition)
> {
> freezer_do_not_count();
> __retval = wait_event_killable(condition);
> freezer_count();
> __retval;
> }
> Do you think it can work?

Yeah, probably. I was hoping to remove count/do_not_count tho.
Hmmm... maybe we can just flip PF_NOFREEZE instead with a bit of
modification, I think.



 \ /
  Last update: 2011-11-01 19:31    [W:0.055 / U:30.984 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site