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    Subject[PATCH 5/6] futex: unlock before returning -EFAULT
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    futex_lock_pi can potentially return -EFAULT with the rt_mutex held.  This
    seems like the wrong thing to do as userspace should assume -EFAULT means the
    lock was not taken. Even if it could figure this out, we'd be leaving the
    pi_state->owner in an inconsistent state. This patch unlocks the rt_mutex
    prior to returning -EFAULT to userspace.

    Build and boot tested on a 4 way Intel x86_64 workstation. Passes basic
    pthread_mutex and PI tests out of ltp/testcases/realtime.

    Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Rusty Russell <rusty@rustcorp.com.au>
    ---

    kernel/futex.c | 7 +++++++
    1 files changed, 7 insertions(+), 0 deletions(-)

    diff --git a/kernel/futex.c b/kernel/futex.c
    index 6579912..c980a55 100644
    --- a/kernel/futex.c
    +++ b/kernel/futex.c
    @@ -1567,6 +1567,13 @@ retry_locked:
    }
    }

    + /*
    + * If fixup_pi_state_owner() faulted and was unable to handle the
    + * fault, unlock it and return the fault to userspace.
    + */
    + if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current))
    + rt_mutex_unlock(&q.pi_state->pi_mutex);
    +
    /* Unqueue and drop the lock */
    unqueue_me_pi(&q);



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