Hello,

On Thu, Oct 25, 2012 at 07:34:33PM +0200, Oleg Nesterov wrote:

quoted

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
tomorrow.

Yeah and maybe explain briefly how schedule_freezable() gets us out of
the trouble.

quoted

quoted

@@ -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?

OOPS.

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
userland tasks.

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.

Thanks.

-- 
tejun