Merge tag 'locking-urgent-2020-11-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip (aaaaa7ec) · Commits · 戴 / test

Pull futex fix from Thomas Gleixner: "A single fix for the futex code where an intermediate state in the underlying RT mutex was not handled correctly and triggering a BUG() instead of treating it as another variant of retry condition" * tag 'locking-urgent-2020-11-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: futex: Handle transient "ownerless" rtmutex state correctly

kernel/futex.c

+14 −2

Original line number	Diff line number	Diff line
		@@ -2380,10 +2380,22 @@ retry:
		}

		/*
		* Since we just failed the trylock; there must be an owner.
		* The trylock just failed, so either there is an owner or
		* there is a higher priority waiter than this one.
		*/
		newowner = rt_mutex_owner(&pi_state->pi_mutex);
		BUG_ON(!newowner);
		/*
		* If the higher priority waiter has not yet taken over the
		* rtmutex then newowner is NULL. We can't return here with
		* that state because it's inconsistent vs. the user space
		* state. So drop the locks and try again. It's a valid
		* situation and not any different from the other retry
		* conditions.
		*/
		if (unlikely(!newowner)) {
		err = -EAGAIN;
		goto handle_err;
		}
		} else {
		WARN_ON_ONCE(argowner != current);
		if (oldowner == current) {

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