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Peter Zijlstra
e548057270
Dan reported that rt_mutex_adjust_prio_chain() can be called with .orig_waiter == NULL however commita055fcc132("locking/rtmutex: Return success on deadlock for ww_mutex waiters") unconditionally dereferences it. Since both call-sites that have .orig_waiter == NULL don't care for the return value, simply disable the deadlock squash by adding the NULL check. Notably, both callers use the deadlock condition as a termination condition for the iteration; once detected, it is sure that (de)boosting is done. Arguably step [3] would be a more natural termination point, but it's dubious whether adding a third deadlock detection state would improve the code. Fixes:a055fcc132("locking/rtmutex: Return success on deadlock for ww_mutex waiters") Reported-by: Dan Carpenter <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Acked-by: Sebastian Andrzej Siewior <[email protected]> Link: https://lore.kernel.org/r/[email protected]