From: Jens Axboe <axboe@kernel.dk>
To: Ted Ts'o <tytso@mit.edu>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>
Subject: Re: What am I doing wrong? submit_bio() suddenly stops working...
Date: Fri, 22 Oct 2010 09:19:37 +0200 [thread overview]
Message-ID: <4CC13B09.6030104@kernel.dk> (raw)
In-Reply-To: <20101022033424.GO3127@thunk.org>
On 2010-10-22 05:34, Ted Ts'o wrote:
> On Thu, Oct 21, 2010 at 07:46:15PM +0200, Jens Axboe wrote:
>> By the sound of things, if I were you I'd turn on the mem and slab
>> debugging to catch use-before-init and use-after-free. Mysterious hangs
>> in the IO sub system are usually caused by such bugs. And the regular
>> debugging aids, just to see if that produces anything of interest.
>
> It looks like it was a use-after-free bug in my code. I'm running a
> full set of set of tests now, but so far, it's gotten a lot further
> than it went before, so I think I've figured it out.
>
> I'm not sure why it caused the weird behaviour that it did (I got as
> far as figuring out that somehow we lost the unplug timer, so after
> the queue got plugged it never got unplugged), but I'm not going to
> ask too many questions. :-)
>
> Maybe later on I'll try to figure out if there's any way to add some
> kind of sanity checking so that screw ups in in the bio code's caller
> cause a clearer failure (such as a BUG_ON), but that'll have to wait
> for when I have some free time.
In my experience, use-after-free bugs are best caught using the
allocator poisoning along with lock checking. I guess that didn't
trigger for you?
Out of curiousity, what was the exact bug?
--
Jens Axboe
next prev parent reply other threads:[~2010-10-22 7:19 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-21 2:00 What am I doing wrong? submit_bio() suddenly stops working Theodore Ts'o
2010-10-21 6:59 ` Jens Axboe
2010-10-21 16:55 ` Ted Ts'o
2010-10-21 17:41 ` Boaz Harrosh
2010-10-21 18:07 ` Jens Axboe
2010-10-22 13:04 ` Peter Zijlstra
2010-10-22 14:08 ` Jens Axboe
2010-10-21 18:14 ` Ted Ts'o
2010-10-21 18:21 ` Jens Axboe
2010-10-21 17:46 ` Jens Axboe
2010-10-21 21:29 ` Ted Ts'o
2010-10-22 3:34 ` Ted Ts'o
2010-10-22 7:19 ` Jens Axboe [this message]
2010-10-23 14:48 ` Ted Ts'o
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