The following commit has been merged into the locking/core branch of tip:

Commit-ID: 8f556a326c93213927e683fc32bbf5be1b62540a Gitweb: https://git.kernel.org/tip/8f556a326c93213927e683fc32bbf5be1b62540a Author: Zqiang qiang1.zhang@intel.com AuthorDate: Fri, 17 Dec 2021 15:42:07 +08:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Sat, 18 Dec 2021 10:55:51 +01:00

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: c3123c431447 ("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 --- 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 0c6a48d..1f25a4d 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;