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    Subject[PATCH RT 17/39] rtmutex.c: Fix incorrect waiter check
    3.14.34-rt32-rc1 stable review patch.
    If anyone has any objections, please let me know.

    ------------------

    From: Brad Mouring <bmouring@ni.com>

    In task_blocks_on_lock, there's a null check on pi_blocked_on
    of the task_struct. This pointer can encode the fact that the
    task that contains the pointer is waking (preventing requeuing)
    and therefore is non-null. Use the inline function to avoid
    dereferencing an invalid "pointer"

    Signed-off-by: Brad Mouring <brad.mouring@ni.com>
    Reported-by: Ben Shelton <ben.shelton@ni.com>
    Reviewed-by: T Makphaibulchoke <tmac@hp.com>
    Tested-by: T Makphaibulchoke <tmac@hp.com>
    Cc: stable-rt@vger.kernel.org
    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    ---
    kernel/locking/rtmutex.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
    index ec72272ab73a..74a824523d3a 100644
    --- a/kernel/locking/rtmutex.c
    +++ b/kernel/locking/rtmutex.c
    @@ -361,7 +361,8 @@ int max_lock_depth = 1024;

    static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p)
    {
    - return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL;
    + return rt_mutex_real_waiter(p->pi_blocked_on) ?
    + p->pi_blocked_on->lock : NULL;
    }

    /*
    --
    2.1.4



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