linux-kernel - [PATCH 0/3] state/exit_state cleanups (Was: Remove unused variable ret from sync_thread

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Message-ID: <20131113143552.GA10517@redhat.com>
Date:	Wed, 13 Nov 2013 15:35:52 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	David Laight <David.Laight@...LAB.COM>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Ingo Molnar <mingo@...nel.org>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 0/3] state/exit_state cleanups (Was: Remove unused variable
	ret from sync_thread_master())

On 11/12, Oleg Nesterov wrote:
>
> On 11/12, Peter Zijlstra wrote:
> >
> > We have to put in something...
> >
> > 	BUILD_BUG_ON(1 + ilog2(TASK_STATE_MAX) != ARRAY_SIZE(task_state_array));
> >
> > However, since we always set it together with TASK_UNINTERUPTIBLE
> > userspace shouldn't actually ever see the I thing.
>
> OOPS. I didn't know that get_task_state() does &= TASK_REPORT. So it
> can never report anything > EXIT_DEAD.
>
> Perhaps we should change BUILD_BUG_ON() and shrink task_state_array?

Seriously, imho this looks confusing enough and deserves a cleanup.


As for "nobody should use exit_state". I'll try to recheck, but iirc
we already discussed this... do you remember any reason why
schedule_debug() can't check prev->state == TASK_DEAD instead of
->exit_state?

Note that ->exit_state is not exactly right, it is set by exit_notify()
but in_atomic_preempt_off() should be only ignored when the task does
the last schedule() in TASK_DEAD.

Oleg.

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