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From: Peter Zijlstra <peterz@infradead.org>
To: Qian Cai <cai@lca.pw>
Cc: Ingo Molnar <mingo@redhat.com>,
	linux kernel <linux-kernel@vger.kernel.org>,
	Oleg Nesterov <oleg@redhat.com>,
	gkohli@codeaurora.org
Subject: Re: kernel BUG at kernel/sched/core.c:3490!
Date: Mon, 7 Jan 2019 14:52:15 +0100	[thread overview]
Message-ID: <20190107135215.GG14122@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <ba9c5ad8-d78c-904d-0430-a67d8e3ea729@lca.pw>

On Tue, Jan 01, 2019 at 12:44:35AM -0500, Qian Cai wrote:
> Running some mmap() workloads to put the system on low memory situation with
> swapping and OOM, and then it trigger this BUG(),
> 
> void __noreturn do_task_dead(void)
> {
>         /* Causes final put_task_struct in finish_task_switch(): */
>         set_special_state(TASK_DEAD);
> 
>         /* Tell freezer to ignore us: */
>         current->flags |= PF_NOFREEZE;
> 
>         __schedule(false);
>         BUG();
> 
>         /* Avoid "noreturn function does return" - but don't continue if BUG()
> is a NOP: */
>         for (;;)
>                 cpu_relax();
> }

This would mean that we somehow loose the TASK_DEAD state before hitting
schedule(), but that is something that should be avoided by
set_special_state(), which is supposed to serialize against concurrent
wake-ups.

Also see commit: b5bf9a90bbeb ("sched/core: Introduce set_special_state()")

How readily does this reproduce?

  reply	other threads:[~2019-01-07 13:52 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-01  5:44 kernel BUG at kernel/sched/core.c:3490! Qian Cai
2019-01-07 13:52 ` Peter Zijlstra [this message]
2019-01-07 14:36   ` Qian Cai
2019-01-07 17:56     ` Oleg Nesterov
2019-01-11 10:37       ` Kohli, Gaurav
2019-01-11 16:17         ` Qian Cai
2019-01-12  8:54           ` Kohli, Gaurav
2019-01-16 17:32             ` Oleg Nesterov

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