Re: [PATCH 09/10] sigtimedwait: use freezable blocking call

From: Oleg Nesterov
Date: Tue Apr 30 2013 - 13:03:41 EST

On 04/30, Colin Cross wrote:
> On Tue, Apr 30, 2013 at 9:38 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> > On 04/29, Colin Cross wrote:
> >>
> >> Avoid waking up every thread sleeping in a sigtimedwait call during
> >> suspend and resume by calling a freezable blocking call.
> >
> > This doesn't explain why do want this change...
> >
> > OK, probably to avoid -EAGAIN from sigtimedwait() if the freezer wakes
> > up the caller.
> See for the full
> justification. I will include a fuller description of the reason for
> this patch in the next version.

Yes, thanks, I already realized what are you trying to do.

> > The task will be interrupted anyway and the syscall will return
> > -EAGAIN, this only changes the time when try_to_freeze() is called.
> >
> > For what? The task will call do_signal/try_to_freeze really "soon".
> See, which removes
> the wakeup sent to skipped tasks, so schedule_timeout_interruptible()
> will only return if the timeout finishes or another task

Or if freeze_task() was already called.

but I guess you do not care.


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