linux-kernel - [PATCH v2] locking/rtmutex: Fix incorrect spinning condition

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Date:   Fri, 17 Dec 2021 15:42:07 +0800
From:   Zqiang <qiang1.zhang@...el.com>
To:     peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        longman@...hat.com
Cc:     linux-kernel@...r.kernel.org, qiang1.zhang@...el.com
Subject: [PATCH v2] locking/rtmutex: Fix incorrect spinning condition

When the lock owner is on CPU and not need resched, the current waiter
need to be checked, if it not longer top the waiter, stop spinning.

Fixes: c3123c431447 ("locking/rtmutex: Dont dereference waiter lockless")
Signed-off-by: Zqiang <qiang1.zhang@...el.com>
---
 v1->v2:
 Modify description information.

 kernel/locking/rtmutex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index 0c1f2e3f019a..8555c4efe97c 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1383,7 +1383,7 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
 		 *  - the VCPU on which owner runs is preempted
 		 */
 		if (!owner_on_cpu(owner) || need_resched() ||
-		    rt_mutex_waiter_is_top_waiter(lock, waiter)) {
+		    !rt_mutex_waiter_is_top_waiter(lock, waiter)) {
 			res = false;
 			break;
 		}
-- 
2.25.1