linux-kernel - Re: [PATCH 4/5] freezer: clear fake signal on exit from _

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Message-ID: <20130223194125.GB9405@redhat.com>
Date:	Sat, 23 Feb 2013 20:41:25 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Mandeep Singh Baines <msb@...omium.org>
Cc:	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Ingo Molnar <mingo@...hat.com>,
	adurbin@...omium.org
Subject: Re: [PATCH 4/5] freezer: clear fake signal on exit from
	__refrigerator

On 02/20, Mandeep Singh Baines wrote:
>
> I think we need something like this in order to be able to fix
> wait_event_freezable and friends. Here is one idea:
>
> #define __wait_event_freezable(wq, condition, ret)                  \
> do {                                                                    \
>         DEFINE_WAIT(__wait);                                            \
>                                                                         \
>         for (;;) {                                                      \
>                 prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE);      \
>                 if (condition)                                          \
>                         break;                                          \
>                 if (!signal_pending(current)) {                         \
>                         freezable_schedule();

...

> If you cleaned up the fake signal in __refrigerator()

Perhaps. Or we can add recalc_sigpending into wait_freezable().
But note that

	if (!signal_pending(current))
		freezable_schedule();

is not actually right, wait_event_freezable() should be interruptible,
but not by freezer.

And let me repeat, as for coredump this can only solve the problems in
wait_for_dump_handler(). As for other users, I simply do not see any
valid user today, so perhaps wait_event_freezable() should die... Or
I missed something.

I'll try to make the coredumping fixes tomorrow, then we discuss this
again.

Oleg.

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