linux-kernel - [PATCH] libcfs: Fix a sleep-in-atomic bug in cfs_wi_sched

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Date:   Wed, 31 May 2017 16:05:15 +0800
From:   Jia-Ju Bai <baijiaju1990@....com>
To:     oleg.drokin@...el.com, andreas.dilger@...el.com,
        jsimmons@...radead.org, gregkh@...uxfoundation.org,
        bobijam.xu@...el.com, dmitry.eremin@...el.com
Cc:     lustre-devel@...ts.lustre.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, Jia-Ju Bai <baijiaju1990@....com>
Subject: [PATCH] libcfs: Fix a sleep-in-atomic bug in cfs_wi_sched_destroy

The driver may sleep under a spin lock, and the function call path is:
cfs_wi_sched_destroy (acquire the lock by spin_lock)
  LASSERT
    lbug_with_loc
      libcfs_debug_dumplog
        schedule and kthread_run --> may sleep

To fix it, all "LASSERT" is placed out of the spin_lock and spin_unlock.

Signed-off-by: Jia-Ju Bai <baijiaju1990@....com>
---
 drivers/staging/lustre/lnet/libcfs/workitem.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/lustre/lnet/libcfs/workitem.c b/drivers/staging/lustre/lnet/libcfs/workitem.c
index dbc2a9b..e0424f6 100644
--- a/drivers/staging/lustre/lnet/libcfs/workitem.c
+++ b/drivers/staging/lustre/lnet/libcfs/workitem.c
@@ -302,11 +302,12 @@ static int cfs_wi_scheduler(void *arg)
 		return;
 	}
 
-	LASSERT(!list_empty(&sched->ws_list));
 	sched->ws_stopping = 1;
 
 	spin_unlock(&cfs_wi_data.wi_glock);
 
+	LASSERT(!list_empty(&sched->ws_list));
+
 	i = 2;
 	wake_up_all(&sched->ws_waitq);
 
-- 
1.7.9.5