[PATCH 1/1] freezer: change ptrace_stop/do_signal_stop to use freezable_schedule()
tj at kernel.org
Thu Oct 25 17:36:32 UTC 2012
On Thu, Oct 25, 2012 at 07:34:33PM +0200, Oleg Nesterov wrote:
> > I think it would be great if the description is more detailed. This
> > code path always makes my head spin and I think we can definitely use
> > some more guiding in understanding this dang thing. :)
> Do you mean describe the race in more details? OK, will do and resend
Yeah and maybe explain briefly how schedule_freezable() gets us out of
> > > @@ -2092,7 +2085,7 @@ static bool do_signal_stop(int signr)
> > > }
> > >
> > > /* Now we don't run again until woken by SIGCONT or SIGKILL */
> > > - schedule();
> > > + freezable_schedule();
> > This makes me wonder whether we still need try_to_freeze() in
> > get_signal_to_deliver() right after the relock: label. Freezer no
> > longer treats STOPPED/TRACED special and both sleeping sites in signal
> > deliver path are marked freezable_schedule(). We shouldn't need the
> > explicit try_to_freeze(), right?
> I'd say this doesn't really matter but yes we can move it up,
> get_signal_to_deliver() will be called again.
Right, we can't remove it. That's our main freezing point for
> But! the comment above try_to_freeze() becomes misleading with
> this patch, so this really needs v2.
But, yeah, I think we should move it above relock: and update the
comment to explain that that's the usual freezing site.
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