From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: mingo@kernel.org, torvalds@linux-foundation.org,
tglx@linutronix.de, ilya.dryomov@inktank.com,
umgwanakikbuti@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 10/11] sched: Debug nested sleeps
Date: Wed, 1 Oct 2014 18:10:58 +0200 [thread overview]
Message-ID: <20141001161058.GE2843@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20140930214732.GA31384@redhat.com>
On Tue, Sep 30, 2014 at 11:47:32PM +0200, Oleg Nesterov wrote:
> > > This is minor, but this way CONFIG_DEBUG_ATOMIC_SLEEP will not imply
> > > a subtle behavioural change.
> >
> > You mean the __set_current_state() that's extra?
>
> Yes, and note that it only does __set_current_state(RUNNING) if
> CONFIG_DEBUG_ATOMIC_SLEEP. This means that disabling/enabling this
> option can, silently hide/uncover a bug.
>
> > I would actually argue
> > to keep that since it makes the 'problem' much worse.
>
> OK, I won't insist, but could you explain why the suggested change can
> make the problem (and which problem ;) worse?
Sure, so the trivial problem is not actually going to sleep in the outer
wait primitive because the inner wait primitive reset ->state to
TASK_RUNNING.
So by always setting the ->state to TASK_RUNNING it never goes to sleep
and it'll revert to spinning, causing spikes in CPU usage that should
hopefully be far easier to notice than the occasional funny.
next prev parent reply other threads:[~2014-10-01 16:11 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-24 8:18 [PATCH 00/11] nested sleeps, fixes and debug infrastructure Peter Zijlstra
2014-09-24 8:18 ` [PATCH 01/11] locking/mutex: Dont assume TASK_RUNNING Peter Zijlstra
2014-10-28 11:09 ` [tip:sched/core] locking/mutex: Don't " tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 02/11] wait: Provide infrastructure to deal with nested blocking Peter Zijlstra
2014-09-29 21:02 ` Oleg Nesterov
2014-10-02 7:37 ` Peter Zijlstra
2014-10-02 21:21 ` Oleg Nesterov
2014-10-28 11:09 ` [tip:sched/core] sched/wait: " tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 03/11] wait: Add might_sleep() Peter Zijlstra
2014-10-28 11:09 ` [tip:sched/core] sched/wait: Add might_sleep() checks tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 04/11] exit: Deal with nested sleeps Peter Zijlstra
2014-10-28 11:10 ` [tip:sched/core] sched, " tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 05/11] inotify: " Peter Zijlstra
2014-10-28 11:10 ` [tip:sched/core] sched, " tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 06/11] tty: " Peter Zijlstra
2014-10-28 11:10 ` [tip:sched/core] sched, " tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 07/11] smp: Correctly deal " Peter Zijlstra
2014-10-28 11:11 ` [tip:sched/core] sched, " tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 08/11] module: Fix nested sleep Peter Zijlstra
2014-09-29 22:18 ` Oleg Nesterov
2014-09-30 13:43 ` Peter Zijlstra
2014-10-28 11:11 ` [tip:sched/core] sched, modules: Fix nested sleep in add_unformed_module() tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 09/11] net: Clean up sk_wait_event() vs might_sleep() Peter Zijlstra
2014-09-24 8:36 ` Peter Zijlstra
2014-10-28 11:11 ` [tip:sched/core] sched, net: Clean up sk_wait_event() vs. might_sleep() tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 10/11] sched: Debug nested sleeps Peter Zijlstra
2014-09-29 22:13 ` Oleg Nesterov
2014-09-30 13:49 ` Peter Zijlstra
2014-09-30 21:47 ` Oleg Nesterov
2014-10-01 16:10 ` Peter Zijlstra [this message]
2014-10-01 18:35 ` Oleg Nesterov
2014-10-02 9:07 ` Peter Zijlstra
2014-10-02 21:34 ` Oleg Nesterov
2014-10-28 11:11 ` [tip:sched/core] " tip-bot for Peter Zijlstra
2014-09-24 8:18 ` [PATCH 11/11] sched: Exclude cond_resched() from nested sleep test Peter Zijlstra
2014-10-28 11:12 ` [tip:sched/core] " tip-bot for Peter Zijlstra
2014-09-25 8:30 ` [PATCH 00/11] nested sleeps, fixes and debug infrastructure Mike Galbraith
2014-09-25 9:06 ` Peter Zijlstra
2014-09-25 9:10 ` Mike Galbraith
2014-09-25 9:15 ` Peter Zijlstra
2014-09-25 9:56 ` Mike Galbraith
2014-09-25 13:59 ` BUG: sleeping function called from invalid context at drivers/cpufreq/cpufreq.c:370 Mike Galbraith
2014-09-26 6:24 ` Mike Galbraith
2014-09-26 7:54 ` Mike Galbraith
2014-09-26 14:10 ` Rafael J. Wysocki
2014-09-26 22:44 ` Rafael J. Wysocki
2014-09-27 6:14 ` Mike Galbraith
2014-09-27 19:57 ` Rafael J. Wysocki
2014-10-02 10:22 ` [PATCH 00/11] nested sleeps, fixes and debug infrastructure Peter Zijlstra
2014-10-02 12:15 ` Peter Zijlstra
2014-10-27 13:41 ` Peter Zijlstra
2014-10-28 0:07 ` Oleg Nesterov
2014-10-28 8:23 ` Peter Zijlstra
2014-10-29 0:00 ` Oleg Nesterov
2014-10-29 9:35 ` Peter Zijlstra
2014-10-29 11:31 ` Peter Zijlstra
2014-10-29 11:36 ` Peter Zijlstra
2014-10-29 14:26 ` Peter Zijlstra
2014-11-04 16:08 ` [tip:sched/core] audit, sched/wait: Fixup kauditd_thread() wait loop tip-bot for Peter Zijlstra
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