From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:38656 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755807AbdLTRVj (ORCPT ); Wed, 20 Dec 2017 12:21:39 -0500 Subject: Patch "md: always set THREAD_WAKEUP and wake up wqueue if thread existed" has been added to the 4.14-stable tree To: gqjiang@suse.com, alexander.levin@verizon.com, gregkh@linuxfoundation.org, shli@fb.com Cc: , From: Date: Wed, 20 Dec 2017 18:20:26 +0100 Message-ID: <15137904262686@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled md: always set THREAD_WAKEUP and wake up wqueue if thread existed to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: md-always-set-thread_wakeup-and-wake-up-wqueue-if-thread-existed.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From foo@baz Wed Dec 20 18:17:52 CET 2017 From: Guoqing Jiang Date: Mon, 9 Oct 2017 10:32:48 +0800 Subject: md: always set THREAD_WAKEUP and wake up wqueue if thread existed From: Guoqing Jiang [ Upstream commit d1d90147c9680aaec4a5757932c2103c42c9c23b ] Since commit 4ad23a976413 ("MD: use per-cpu counter for writes_pending"), the wait_queue is only got invoked if THREAD_WAKEUP is not set previously. With above change, I can see process_metadata_update could always hang on the wait queue, because mddev->thread could stay on 'D' status and the THREAD_WAKEUP flag is not cleared since there are lots of place to wake up mddev->thread. Then deadlock happened as follows: linux175:~ # ps aux|grep md|grep D root 20117 0.0 0.0 0 0 ? D 03:45 0:00 [md0_raid1] root 20125 0.0 0.0 0 0 ? D 03:45 0:00 [md0_cluster_rec] linux175:~ # cat /proc/20117/stack [] dlm_lock_sync+0x94/0xd0 [md_cluster] [] lock_token+0x34/0xd0 [md_cluster] [] metadata_update_start+0x64/0x110 [md_cluster] [] md_update_sb.part.58+0x9b/0x860 [md_mod] [] md_update_sb+0x15/0x30 [md_mod] [] md_check_recovery+0x266/0x490 [md_mod] [] raid1d+0x42/0x810 [raid1] [] md_thread+0x122/0x150 [md_mod] [] kthread+0x101/0x140 linux175:~ # cat /proc/20125/stack [] recv_daemon+0x3f9/0x5c0 [md_cluster] [] md_thread+0x122/0x150 [md_mod] [] kthread+0x101/0x140 So let's revert the part of code in the commit to resovle the problem since we can't get lots of benefits of previous change. Fixes: 4ad23a976413 ("MD: use per-cpu counter for writes_pending") Signed-off-by: Guoqing Jiang Signed-off-by: Shaohua Li Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/md/md.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -7468,8 +7468,8 @@ void md_wakeup_thread(struct md_thread * { if (thread) { pr_debug("md: waking up MD thread %s.\n", thread->tsk->comm); - if (!test_and_set_bit(THREAD_WAKEUP, &thread->flags)) - wake_up(&thread->wqueue); + set_bit(THREAD_WAKEUP, &thread->flags); + wake_up(&thread->wqueue); } } EXPORT_SYMBOL(md_wakeup_thread); Patches currently in stable-queue which might be from gqjiang@suse.com are queue-4.14/md-always-set-thread_wakeup-and-wake-up-wqueue-if-thread-existed.patch