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From: Peter Zijlstra <peterz@infradead.org>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
	syzbot <syzbot+7b2866454055e43c21e5@syzkaller.appspotmail.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk
Subject: Re: INFO: task hung in __sb_start_write
Date: Mon, 11 Jun 2018 09:30:38 +0200	[thread overview]
Message-ID: <20180611073038.GK12217@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <ee29ad1e-8bd0-3eef-f49e-793bfadcbea7@I-love.SAKURA.ne.jp>

On Sun, Jun 10, 2018 at 11:47:56PM +0900, Tetsuo Handa wrote:

> This looks quite strange that nobody is holding percpu_rw_semaphore for
> write but everybody is stuck trying to hold it for read. (Since there
> is no "X locks held by ..." line without followup "#0:" line, there is
> no possibility that somebody is in TASK_RUNNING state while holding
> percpu_rw_semaphore for write.)
> 
> I feel that either API has a bug or API usage is wrong.
> Any idea for debugging this?

Look at percpu_rwsem_release() and usage. The whole fs freezer thing is
magic.

  reply	other threads:[~2018-06-11  7:30 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-03 10:17 INFO: task hung in __sb_start_write syzbot
2018-06-10 14:47 ` Tetsuo Handa
2018-06-11  7:30   ` Peter Zijlstra [this message]
2018-06-11  7:39     ` Dmitry Vyukov
2018-06-14 10:33       ` Tetsuo Handa
2018-06-14 10:33         ` Tetsuo Handa
2018-06-15  9:19         ` Dmitry Vyukov
2018-06-15 19:40           ` Tetsuo Handa
2018-06-19 11:10             ` Tetsuo Handa
2018-06-19 11:47               ` Dmitry Vyukov
2018-06-19 13:00                 ` Tetsuo Handa
2018-07-11 11:13               ` Tetsuo Handa
2018-07-13 10:38                 ` Tetsuo Handa

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