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%3Ba=su...

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 stable@vger.kernel.org know about it.

From foo@baz Wed Dec 20 18:17:52 CET 2017

From: Guoqing Jiang gqjiang@suse.com 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 gqjiang@suse.com

[ 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 [<ffffffffa0635604>] dlm_lock_sync+0x94/0xd0 [md_cluster] [<ffffffffa0635674>] lock_token+0x34/0xd0 [md_cluster] [<ffffffffa0635804>] metadata_update_start+0x64/0x110 [md_cluster] [<ffffffffa04d985b>] md_update_sb.part.58+0x9b/0x860 [md_mod] [<ffffffffa04da035>] md_update_sb+0x15/0x30 [md_mod] [<ffffffffa04dc066>] md_check_recovery+0x266/0x490 [md_mod] [<ffffffffa06450e2>] raid1d+0x42/0x810 [raid1] [<ffffffffa04d2252>] md_thread+0x122/0x150 [md_mod] [<ffffffff81091741>] kthread+0x101/0x140 linux175:~ # cat /proc/20125/stack [<ffffffffa0636679>] recv_daemon+0x3f9/0x5c0 [md_cluster] [<ffffffffa04d2252>] md_thread+0x122/0x150 [md_mod] [<ffffffff81091741>] 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 gqjiang@suse.com Signed-off-by: Shaohua Li shli@fb.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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