Commit 8f556a32 authored by Zqiang's avatar Zqiang Committed by Thomas Gleixner

locking/rtmutex: Fix incorrect condition in rtmutex_spin_on_owner()

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: c3123c43 ("locking/rtmutex: Dont dereference waiter lockless")
Signed-off-by: default avatarZqiang <qiang1.zhang@intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211217074207.77425-1-qiang1.zhang@intel.com
parent 2585cf9d
...@@ -1380,7 +1380,7 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock, ...@@ -1380,7 +1380,7 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
* - the VCPU on which owner runs is preempted * - the VCPU on which owner runs is preempted
*/ */
if (!owner->on_cpu || need_resched() || 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))) { vcpu_is_preempted(task_cpu(owner))) {
res = false; res = false;
break; break;
......
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