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locking/rtmutex: Fix incorrect condition in rtmutex_spin_on_owner()

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commit 8f556a326c upstream.

Optimistic spinning needs to be terminated when the spinning waiter is not
longer the top waiter on the lock, but the condition is negated. It
terminates if the waiter is the top waiter, which is defeating the whole
purpose.

Fixes: c3123c4314 ("locking/rtmutex: Dont dereference waiter lockless")
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211217074207.77425-1-qiang1.zhang@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Zqiang 2021-12-17 15:42:07 +08:00 • committed by Justin Hammond
parent fd6672eb03
commit 65da1c2d35
1 changed files with 1 additions and 1 deletions
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2
kernel/locking/rtmutex.c
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@ -1373,7 +1373,7 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
* - the VCPU on which owner runs is preempted
*/
if (!owner->on_cpu || need_resched() ||
rt_mutex_waiter_is_top_waiter(lock, waiter) ||
!rt_mutex_waiter_is_top_waiter(lock, waiter) ||
vcpu_is_preempted(task_cpu(owner))) {
res = false;
break;