From: Shaohua Li <shli@fb.com>
Date: Thu, 25 Feb 2016 01:41:01 +0000 (-0800)
Subject: MD: warn for potential deadlock
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=70d9798b95562abac005d4ba71d28820f9a201eb;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

MD: warn for potential deadlock

The personality thread shouldn't call mddev_suspend(). Because
mddev_suspend() will for all IO finish, but IO is handled in personality
thread, so this could cause deadlock. To trigger this early, add a
warning if mddev_suspend() is called from personality thread.

Suggested-by: NeilBrown <neilb@suse.com>
Cc: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>
---

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 464627b7e820..c068f171b4eb 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -305,6 +305,7 @@ static blk_qc_t md_make_request(struct request_queue *q, struct bio *bio)
  */
 void mddev_suspend(struct mddev *mddev)
 {
+	WARN_ON_ONCE(current == mddev->thread->tsk);
 	if (mddev->suspended++)
 		return;
 	synchronize_rcu();