From 7de67db39a68e3f7ab7b471f6f0661097fb4241e Mon Sep 17 00:00:00 2001 From: Zqiang Date: Fri, 17 Dec 2021 15:42:07 +0800 Subject: [PATCH] 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: da048d94ddee ("locking/rtmutex: Dont dereference waiter lockless") Signed-off-by: Zqiang Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20211217074207.77425-1-qiang1.zhang@intel.com --- 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 0c6a48dfcecb3..1f25a4d7de273 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1380,7 +1380,7 @@ 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; -- 2.39.5