From: Al Viro <viro@ZenIV.linux.org.uk>
To: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Mark Jackson <mpfj-list@mimc.co.uk>,
linux-next@vger.kernel.org, linux-mtd@lists.infradead.org,
David Woodhouse <dwmw2@infradead.org>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: linux-next: JFFS2 deadlock
Date: Wed, 27 Feb 2013 00:27:55 +0000 [thread overview]
Message-ID: <20130227002755.GL4503@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20130227101704.90466ae6df78ab9b3aa4ba22@canb.auug.org.au>
On Wed, Feb 27, 2013 at 10:17:04AM +1100, Stephen Rothwell wrote:
> Hi Mark,
>
> On Tue, 26 Feb 2013 11:54:56 +0000 Mark Jackson <mpfj-list@mimc.co.uk> wrote:
> >
> > Just tested the current next-20130226 on a custom AM335X board, and I received the JFFS2 deadlock shown below.
>
> Is this new today? is it reproducible? Does if ail for Linus' tree?
>
> Al, could this be something to do with the new stuff in the vfs tree?
Very unlikely. jffs2_readdir() does, indeed, grab ->sem on the inode in
question and then calls the callback (which might fault, grabbing ->mmap_sem).
Had been doing that all along. And if the userland area we are doing
getdents(2) into had been mmapped from jffs2 file, jffs2_readpage() would
be called, which would grab ->sem on the inode of file mmaped in there.
Again, that had been going on all along. Unlike the situation with ->i_mutex,
this one is probably a false positive - ->sem on directories nests outside of
->mmap_sem, ->sem on non-directories - inside. But that false positive
shouldn't be something new; hell, both paths are present in 2.6.12 with
the lock orders as in the current tree (except that ->sem used to be
a semaphore instead of a mutex).
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: linux-mtd@lists.infradead.org, linux-next@vger.kernel.org,
Mark Jackson <mpfj-list@mimc.co.uk>,
David Woodhouse <dwmw2@infradead.org>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: linux-next: JFFS2 deadlock
Date: Wed, 27 Feb 2013 00:27:55 +0000 [thread overview]
Message-ID: <20130227002755.GL4503@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20130227101704.90466ae6df78ab9b3aa4ba22@canb.auug.org.au>
On Wed, Feb 27, 2013 at 10:17:04AM +1100, Stephen Rothwell wrote:
> Hi Mark,
>
> On Tue, 26 Feb 2013 11:54:56 +0000 Mark Jackson <mpfj-list@mimc.co.uk> wrote:
> >
> > Just tested the current next-20130226 on a custom AM335X board, and I received the JFFS2 deadlock shown below.
>
> Is this new today? is it reproducible? Does if ail for Linus' tree?
>
> Al, could this be something to do with the new stuff in the vfs tree?
Very unlikely. jffs2_readdir() does, indeed, grab ->sem on the inode in
question and then calls the callback (which might fault, grabbing ->mmap_sem).
Had been doing that all along. And if the userland area we are doing
getdents(2) into had been mmapped from jffs2 file, jffs2_readpage() would
be called, which would grab ->sem on the inode of file mmaped in there.
Again, that had been going on all along. Unlike the situation with ->i_mutex,
this one is probably a false positive - ->sem on directories nests outside of
->mmap_sem, ->sem on non-directories - inside. But that false positive
shouldn't be something new; hell, both paths are present in 2.6.12 with
the lock orders as in the current tree (except that ->sem used to be
a semaphore instead of a mutex).
next prev parent reply other threads:[~2013-02-27 0:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-26 11:54 linux-next: JFFS2 deadlock Mark Jackson
2013-02-26 11:54 ` Mark Jackson
2013-02-26 23:17 ` Stephen Rothwell
2013-02-26 23:17 ` Stephen Rothwell
2013-02-27 0:27 ` Al Viro [this message]
2013-02-27 0:27 ` Al Viro
2013-02-27 15:19 ` Mark Jackson
2013-02-27 15:19 ` Mark Jackson
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