Messages in this thread | | | Subject | Re: [PATCH RFC] rtmutex: Permit rt_mutex_unlock() to be invoked with irqs disabled | From | Peter Zijlstra <> | Date | Thu, 21 Jul 2011 13:32:48 +0200 |
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On Tue, 2011-07-19 at 13:14 -0700, Paul E. McKenney wrote: > Because rcu_read_unlock() can be invoked with interrupts disabled, it can > in turn invoke rt_mutex_unlock() with interrupts disabled. This situation > results in lockdep splats (https://lkml.org/lkml/2011/7/7/362) because the > rt_mutex structure's ->lock_wait is acquired elsewhere without disabling > interrupts, which can result in deadlocks. > > This commit therefore changes the rt_mutex structure's ->lock_wait > acquisitions to disable interrupts. > > An alternative fix is to prohibit invoking rcu_read_unlock() with > interrupts disabled unless the entire preceding RCU read-side critical > section has run with interrupts disabled. However, there is already > at least one case in mainline where this potential rule is violated, > and there might well be many more. These would likely be found one at > a time using the lockdep-water-torture method, hence the alternative > fix in the form of this commit.
Thomas, I'm inclined to merge this, any objections?
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