From: Bart Van Assche <bvanassche@acm.org>
To: Jens Axboe <axboe@kernel.dk>,
Damien Le Moal <Damien.LeMoal@wdc.com>,
"fio@vger.kernel.org" <fio@vger.kernel.org>
Subject: Re: [PATCH] zbd: Restore check_swd()
Date: Fri, 28 Sep 2018 13:25:04 -0700 [thread overview]
Message-ID: <1538166304.53591.6.camel@acm.org> (raw)
In-Reply-To: <b3169357-303b-30e2-9018-d889e53c6a97@kernel.dk>
On Fri, 2018-09-28 at 08:54 -0600, Jens Axboe wrote:
> + for (z = zb; z < ze; z++) {
> + pthread_mutex_lock(&z->mutex);
> + swd += z->wp - z->start;
> + }
> + pthread_mutex_lock(&f->zbd_info->mutex);
>
> Can 'z' ever end up being f->zbd_info? That would surely explain the
> deadlock.
Hi Jens,
f->zbd_info and z have a different type so unless something very weird is going
on &z->mutex can't be identical to &f->zbd_info->mutex.
What I think is going on is traditional lock inversion: check_swd() triggers
lock inversion if it is called while any of the z->mutex objects are held. One
such mutex is held where Damien tried to restore the calls of this function. I
will submit a patch that inserts these calls elsewhere.
Bart.
next prev parent reply other threads:[~2018-09-28 20:25 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-27 2:16 [PATCH] zbd: Restore check_swd() Damien Le Moal
2018-09-28 3:41 ` Bart Van Assche
2018-09-28 3:53 ` Jens Axboe
2018-09-28 4:04 ` Damien Le Moal
2018-09-28 5:48 ` Damien Le Moal
2018-09-28 14:54 ` Jens Axboe
2018-09-28 20:25 ` Bart Van Assche [this message]
2018-09-28 20:31 ` Jens Axboe
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