[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20081215184440.GI32491@kernel.dk>
Date: Mon, 15 Dec 2008 19:44:41 +0100
From: Jens Axboe <jens.axboe@...cle.com>
To: Alexander Beregalov <a.beregalov@...il.com>
Cc: "linux-next@...r.kernel.org" <linux-next@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: next-20081215: kernel BUG at block/cfq-iosched.c:1243
On Mon, Dec 15 2008, Alexander Beregalov wrote:
> 2008/12/15 Jens Axboe <jens.axboe@...cle.com>:
> >> [ 23.080733] kernel BUG at block/cfq-iosched.c:1243!
> >> [ 23.080733] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
>
> > Odd, is it reproducible? What is your .config?
> Yes, it is
>
> Config is in attach
It's weird, because the only change for CFQ in that area is the one
below. Does the oops go away if you back this out?
>From 030a3f02bb42fad91ae84c99924fe3ee162a634d Mon Sep 17 00:00:00 2001
From: Jens Axboe <jens.axboe@...cle.com>
Date: Fri, 12 Dec 2008 15:56:31 +0100
Subject: [PATCH] cfq-iosched: fix race between exiting queue and exiting task
Original patch from Nikanth Karthikesan <knikanth@...e.de>
When a queue exits the queue lock is taken and cfq_exit_queue() would free all
the cic's associated with the queue.
But when a task exits, cfq_exit_io_context() gets cic one by one and then
locks the associated queue to call __cfq_exit_single_io_context. It looks like
between getting a cic from the ioc and locking the queue, the queue might have
exited on another cpu.
Fix this by rechecking the cfq_io_context queue key inside the queue lock
again, and not calling into __cfq_exit_single_io_context() if somebody
beat us to it.
Signed-off-by: Jens Axboe <jens.axboe@...cle.com>
---
block/cfq-iosched.c | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index ee8a90c..8a2485d 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1314,7 +1314,16 @@ static void cfq_exit_single_io_context(struct io_context *ioc,
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
+
+ /*
+ * Ensure we get a fresh copy of the ->key to prevent
+ * race between exiting task and queue
+ */
+ smp_read_barrier_depends();
+ if (cic->key)
+ __cfq_exit_single_io_context(cfqd, cic);
__cfq_exit_single_io_context(cfqd, cic);
+
spin_unlock_irqrestore(q->queue_lock, flags);
}
}
--
1.6.0.4.755.g6e139
--
Jens Axboe
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists