From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] blk: fix a wrong accounting of hd_struct->in_flight
Date: Thu, 14 Oct 2010 16:30:41 -0700 [thread overview]
Message-ID: <20101014233041.GJ2447@linux.vnet.ibm.com> (raw)
In-Reply-To: <4CB6FB30.1000502@kernel.dk>
On Thu, Oct 14, 2010 at 02:44:32PM +0200, Jens Axboe wrote:
> On 2010-10-14 08:07, KOSAKI Motohiro wrote:
> >> @@ -1268,7 +1270,17 @@ static int __make_request(struct request
> >> * not touch req->buffer either...
> >> */
> >> req->buffer = bio_data(bio);
> >> + src_part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
> >> req->__sector = bio->bi_sector;
> >> + dst_part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
> >
> > I think this is wrong. disk_map_sector_rcu() require
> > rcu read lock held (see function comment). all other call site take
> > part_stat_lock() before disk_map_sector_rcu() call.
>
> It's called under the queue lock with irqs disabled, which implies a
> rcu critical section.
Having irqs disabled does imply an rcu_read_lock_sched() or an
rcu_read_lock_bh(), but not an rcu_read_lock(), especially if
CONFIG_PREEMPT_RCU.
So an explicit rcu_read_lock() does seem to be needed here.
Thanx, Paul
next prev parent reply other threads:[~2010-10-14 23:30 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-12 6:38 [PATCH] blk: fix a wrong accounting of hd_struct->in_flight Yasuaki Ishimatsu
2010-10-12 8:19 ` Jens Axboe
2010-10-14 12:48 ` [PATCH v2] " Yasuaki Ishimatsu
2010-10-14 12:55 ` Jens Axboe
2010-10-15 8:39 ` [PATCH v3] " Yasuaki Ishimatsu
2010-10-15 10:04 ` Jens Axboe
2010-10-18 8:28 ` [PATCH v4] " Yasuaki Ishimatsu
2010-10-18 8:34 ` Jens Axboe
2010-10-18 12:19 ` [PATCH v5] " Yasuaki Ishimatsu
2010-10-18 12:21 ` Jens Axboe
2010-10-19 2:22 ` Yasuaki Ishimatsu
2010-10-19 10:02 ` Jens Axboe
2010-10-14 6:07 ` [PATCH] " KOSAKI Motohiro
2010-10-14 12:44 ` Jens Axboe
2010-10-14 23:30 ` Paul E. McKenney [this message]
2010-10-15 7:30 ` Jens Axboe
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