Commit 5e14b8b2 authored by Zqiang's avatar Zqiang Committed by Greg Kroah-Hartman
Browse files

locking/rtmutex: Fix incorrect condition in rtmutex_spin_on_owner() 



commit 8f556a32 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: 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


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c63433a0

kernel/locking/rtmutex.c

+1 −1
Original line number Diff line number Diff line
@@ -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;