From patchwork Mon Dec 10 14:20:07 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Herton Ronaldo Krzesinski X-Patchwork-Id: 204920 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from chlorine.canonical.com (chlorine.canonical.com [91.189.94.204]) by ozlabs.org (Postfix) with ESMTP id 502162C0168 for ; Tue, 11 Dec 2012 01:20:24 +1100 (EST) Received: from localhost ([127.0.0.1] helo=chlorine.canonical.com) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1Ti4DQ-00047G-TU; Mon, 10 Dec 2012 14:20:17 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by chlorine.canonical.com with esmtp (Exim 4.71) (envelope-from ) id 1Ti4DL-00043A-DQ for kernel-team@lists.ubuntu.com; Mon, 10 Dec 2012 14:20:11 +0000 Received: from [186.212.211.197] (helo=canonical.com) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1Ti4DK-0006qW-4X; Mon, 10 Dec 2012 14:20:10 +0000 From: Herton Ronaldo Krzesinski To: Jens Axboe Subject: [ 3.5.y.z extended stable ] Patch "dm: fix deadlock with request based dm and queue request_fn" has been added to staging queue Date: Mon, 10 Dec 2012 12:20:07 -0200 Message-Id: <1355149207-9485-1-git-send-email-herton.krzesinski@canonical.com> X-Mailer: git-send-email 1.7.9.5 X-Extended-Stable: 3.5 Cc: kernel-team@lists.ubuntu.com, Alasdair G Kergon X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.13 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: kernel-team-bounces@lists.ubuntu.com Errors-To: kernel-team-bounces@lists.ubuntu.com This is a note to let you know that I have just added a patch titled dm: fix deadlock with request based dm and queue request_fn to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.5.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Herton ------ From fdcb10668dc4539e4c38afbcb4714d542e3c5401 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 6 Nov 2012 12:24:26 +0100 Subject: [PATCH] dm: fix deadlock with request based dm and queue request_fn recursion commit a8c32a5c98943d370ea606a2e7dc04717eb92206 upstream. Request based dm attempts to re-run the request queue off the request completion path. If used with a driver that potentially does end_io from its request_fn, we could deadlock trying to recurse back into request dispatch. Fix this by punting the request queue run to kblockd. Tested to fix a quickly reproducible deadlock in such a scenario. Acked-by: Alasdair G Kergon Signed-off-by: Jens Axboe Signed-off-by: Herton Ronaldo Krzesinski --- drivers/md/dm.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) -- 1.7.9.5 diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 9ff3019..32370ea 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -754,8 +754,14 @@ static void rq_completed(struct mapped_device *md, int rw, int run_queue) if (!md_in_flight(md)) wake_up(&md->wait); + /* + * Run this off this callpath, as drivers could invoke end_io while + * inside their request_fn (and holding the queue lock). Calling + * back into ->request_fn() could deadlock attempting to grab the + * queue lock again. + */ if (run_queue) - blk_run_queue(md->queue); + blk_run_queue_async(md->queue); /* * dm_put() must be at the end of this function. See the comment above