From: Zqiang Date: Fri, 17 Dec 2021 07:42:07 +0000 (+0800) Subject: locking/rtmutex: Fix incorrect condition in rtmutex_spin_on_owner() X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=5e14b8b2680a409165a1a94013961c998c5c61cb;p=linux.git locking/rtmutex: Fix incorrect condition in rtmutex_spin_on_owner() commit 8f556a326c93213927e683fc32bbf5be1b62540a 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: c3123c431447 ("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 Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 6bb116c559b4a..ea5a701ab2408 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -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;