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    SubjectRe: [PATCH RFC] rtmutex: Permit rt_mutex_unlock() to be invoked with irqs disabled
    On Sat, 23 Jul 2011, Paul E. McKenney wrote:

    > On Thu, Jul 21, 2011 at 01:32:48PM +0200, Peter Zijlstra wrote:
    > > 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?
    >
    > FWIW, it has been passing tests here.

    If it's only the unlock path, I'm fine with that change.

    Acked-by-me


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