Messages in this thread | | | Date | Mon, 11 Jul 2022 11:34:57 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v3] locking/rtmutex: Limit # of lock stealing for non-RT waiters |
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On Wed, Jul 06, 2022 at 09:59:16AM -0400, Waiman Long wrote: > Commit 48eb3f4fcfd3 ("locking/rtmutex: Implement equal priority lock > stealing") allows unlimited number of lock stealing's for non-RT > tasks. That can lead to lock starvation of non-RT top waiter tasks if > there is a constant incoming stream of non-RT lockers. This can cause > rcu_preempt self-detected stall or even task lockup in PREEMPT_RT kernel. > For example, > > [77107.424943] rcu: INFO: rcu_preempt self-detected stall on CPU > [ 1249.921363] INFO: task systemd:2178 blocked for more than 622 seconds. > > Avoiding this problem and ensuring forward progress by limiting the > number of times that a lock can be stolen from each waiter. This patch > sets a threshold of 32. That number is arbitrary and can be changed > if needed. >
Why not do the same thing we do for regular mutexes?
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