From: Al Viro <viro@ZenIV.linux.org.uk>
To: Jeff Harris <jefftharris@gmail.com>
Cc: linux-mtd@lists.infradead.org,
David Woodhouse <dwmw2@infradead.org>,
linux-kernel@vger.kernel.org, Jeff Harris <jharris@westell.com>
Subject: Re: [PATCH] jffs2: Re-enable write-buffering after filesystem sync
Date: Fri, 1 Aug 2014 17:56:07 +0100 [thread overview]
Message-ID: <20140801165607.GM18016@ZenIV.linux.org.uk> (raw)
In-Reply-To: <1406909172-7219-1-git-send-email-jharris@westell.com>
On Fri, Aug 01, 2014 at 12:06:12PM -0400, Jeff Harris wrote:
> + spin_lock(&c->wbuf_dwork_lock);
> cancel_delayed_work_sync(&c->wbuf_dwork);
Umm... Usually ..._sync in function name is a sign of potential sleeper,
and calling those under a spinlock is a bad idea.
And looking at the definition of cancel_delayed_work_sync() turns up the
following call chain: cancel_delayed_work_sync() -> __cancel_work_timer() ->
flush_work() -> wait_for_completion(), which definitely isn't something
you should ever do under a spinlock.
While we are at it, you follow that with
> + c->wbuf_queued = 0;
> + spin_lock(&c->wbuf_dwork_lock);
which would be broken even if cancel_delayed_work_sync() hadn't blocked.
That's easily fixed, of course, (s/lock/unlock/). cancel_delayed_work_sync()
under a spinlock is more serious...
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Jeff Harris <jefftharris@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>,
linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
Jeff Harris <jharris@westell.com>
Subject: Re: [PATCH] jffs2: Re-enable write-buffering after filesystem sync
Date: Fri, 1 Aug 2014 17:56:07 +0100 [thread overview]
Message-ID: <20140801165607.GM18016@ZenIV.linux.org.uk> (raw)
In-Reply-To: <1406909172-7219-1-git-send-email-jharris@westell.com>
On Fri, Aug 01, 2014 at 12:06:12PM -0400, Jeff Harris wrote:
> + spin_lock(&c->wbuf_dwork_lock);
> cancel_delayed_work_sync(&c->wbuf_dwork);
Umm... Usually ..._sync in function name is a sign of potential sleeper,
and calling those under a spinlock is a bad idea.
And looking at the definition of cancel_delayed_work_sync() turns up the
following call chain: cancel_delayed_work_sync() -> __cancel_work_timer() ->
flush_work() -> wait_for_completion(), which definitely isn't something
you should ever do under a spinlock.
While we are at it, you follow that with
> + c->wbuf_queued = 0;
> + spin_lock(&c->wbuf_dwork_lock);
which would be broken even if cancel_delayed_work_sync() hadn't blocked.
That's easily fixed, of course, (s/lock/unlock/). cancel_delayed_work_sync()
under a spinlock is more serious...
next prev parent reply other threads:[~2014-08-01 16:57 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-01 16:06 [PATCH] jffs2: Re-enable write-buffering after filesystem sync Jeff Harris
2014-08-01 16:56 ` Al Viro [this message]
2014-08-01 16:56 ` Al Viro
2014-08-01 17:15 ` Jeff Harris
2014-08-01 17:15 ` Jeff Harris
2014-08-01 19:13 ` Al Viro
2014-08-01 19:13 ` Al Viro
2014-08-04 18:02 ` Jeff Harris
2014-08-04 18:02 ` Jeff Harris
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