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

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Message-Id: <1496217186-16701-1-git-send-email-baijiaju1990@163.com>
Date:   Wed, 31 May 2017 15:53:06 +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_schedule

The driver may sleep under a spin lock, and the function call path is:
cfs_wi_schedule (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 |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/lustre/lnet/libcfs/workitem.c b/drivers/staging/lustre/lnet/libcfs/workitem.c
index dbc2a9b..30d28cd 100644
--- a/drivers/staging/lustre/lnet/libcfs/workitem.c
+++ b/drivers/staging/lustre/lnet/libcfs/workitem.c
@@ -179,12 +179,12 @@ struct cfs_wi_sched {
 {
 	LASSERT(!in_interrupt()); /* because we use plain spinlock */
 	LASSERT(!sched->ws_stopping);
+	if (!wi->wi_scheduled)
+		LASSERT(list_empty(&wi->wi_list));
 
 	spin_lock(&sched->ws_lock);
 
 	if (!wi->wi_scheduled) {
-		LASSERT(list_empty(&wi->wi_list));
-
 		wi->wi_scheduled = 1;
 		sched->ws_nscheduled++;
 		if (!wi->wi_running) {
@@ -195,8 +195,8 @@ struct cfs_wi_sched {
 		}
 	}
 
-	LASSERT(!list_empty(&wi->wi_list));
 	spin_unlock(&sched->ws_lock);
+	LASSERT(!list_empty(&wi->wi_list));
 }
 EXPORT_SYMBOL(cfs_wi_schedule);
 
-- 
1.7.9.5