From: Boqun Feng <boqun.feng@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sedat Dilek <sedat.dilek@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Theodore Ts'o" <tytso@mit.edu>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
Subject: Re: [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260
Date: Sun, 27 Mar 2016 21:32:08 +0800 [thread overview]
Message-ID: <20160327133208.GA14802@fixme-laptop.cn.ibm.com> (raw)
In-Reply-To: <CA+55aFw-YXACVasN4n0h03QWgWWwvBray2fcMScAnEn0Wy_Ohw@mail.gmail.com>
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On Sun, Mar 27, 2016 at 05:03:44AM -0700, Linus Torvalds wrote:
> On Sun, Mar 27, 2016 at 1:57 AM, Sedat Dilek <sedat.dilek@gmail.com> wrote:
> >
> > I pulled ext4.git#dev on top of Linux v4.6-rc1...
> >
> > ... and did not see the call-trace.
>
> Unless you're using overlayfs or per-file encryption, I'm not seeing
> that any of that should make any difference (but it's entirely
> possible I'm missing something).
>
> Was it entirely repeatable before? Maybe it just happened to happen
> without that update, and then happened to _not_ happen after you
> rebooted with that 'dev' branch pulled in?
>
> Anyway, I don't think that DEBUG_LOCKS_WARN_ON() in
>
> kernel/locking/lockdep.c:2017 __lock_acquire
>
The code here is in check_no_collision(), so IIUC, there was a warning
because a real chain_key collision happened.
And chain_key is a hashsum of the ->class_idx of held_lock, calculated
via iterate_chain_key(), and the ->class_idx of a held_lock may change
from run to run IIUC, depending on the time register_lock_class() is
called for the corresponding lock class.
So this might be why Sedat didn't see the call-trace again.
Of course, I may miss something subtle here, so add the author of
check_no_collision() in CCs ;-)
If I'm right, maybe we can provide more informative dmesg here rather
than calling DEBUG_LOCKS_WARN_ON() directly?
Regards,
Boqun
> would be an ext4 issue, it looks more like an internal lockdep issue.
>
> Adding in the lockdep people, who will set me right.
>
> Linus
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next prev parent reply other threads:[~2016-03-27 13:33 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-27 8:15 [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260 Sedat Dilek
2016-03-27 8:57 ` Sedat Dilek
2016-03-27 12:03 ` Linus Torvalds
2016-03-27 13:32 ` Boqun Feng [this message]
2016-03-27 18:23 ` Theodore Ts'o
2016-03-27 19:40 ` Sedat Dilek
[not found] ` <CA+55aFwoKRpgq8OCTxUaP+8gOg-mnN3nbruYgiK32a=C5U4TkQ@mail.gmail.com>
2016-03-27 20:24 ` Sedat Dilek
2016-03-27 20:48 ` Peter Zijlstra
2016-03-27 20:59 ` Sedat Dilek
2016-03-27 21:48 ` Sedat Dilek
2016-03-28 1:05 ` Boqun Feng
2016-03-28 6:33 ` Peter Zijlstra
2016-03-29 8:47 ` Ingo Molnar
2016-03-30 9:20 ` Sedat Dilek
2016-03-30 9:36 ` Sedat Dilek
2016-03-30 9:36 ` Peter Zijlstra
2016-03-30 9:49 ` Sedat Dilek
2016-03-30 10:33 ` Sedat Dilek
2016-03-30 12:43 ` Peter Zijlstra
2016-03-30 12:46 ` Sedat Dilek
2016-03-30 13:15 ` Peter Zijlstra
2016-03-30 9:50 ` Peter Zijlstra
2016-03-30 9:59 ` Boqun Feng
2016-03-30 10:36 ` Peter Zijlstra
2016-03-30 11:07 ` Sedat Dilek
2016-03-31 15:42 ` Peter Zijlstra
2016-03-31 15:52 ` Boqun Feng
2016-04-02 6:26 ` Sedat Dilek
2016-03-30 14:06 ` Peter Zijlstra
2016-03-30 15:21 ` Sedat Dilek
2016-03-30 17:03 ` [PATCH] lockdep: print chain_key collision information Alfredo Alvarez Fernandez
2016-03-30 17:19 ` Peter Zijlstra
2016-04-01 6:36 ` [tip:core/urgent] locking/lockdep: Print " tip-bot for Alfredo Alvarez Fernandez
2016-05-10 9:09 ` Peter Zijlstra
2016-04-04 15:31 ` [Linux-v4.6-rc1] ext4: WARNING: CPU: 2 PID: 2692 at kernel/locking/lockdep.c:2017 __lock_acquire+0x180e/0x2260 Sedat Dilek
2016-04-04 16:02 ` Peter Zijlstra
2016-05-09 11:37 ` Sedat Dilek
2016-06-03 15:15 ` Sedat Dilek
2016-04-23 12:54 ` [tip:locking/urgent] lockdep: Fix lock_chain::base size tip-bot for Peter Zijlstra
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