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    Subject[PATCH RT 14/39] futex: Split out the first waiter attachment from lookup_pi_state()
    3.14.34-rt32-rc1 stable review patch.
    If anyone has any objections, please let me know.

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

    From: Thomas Gleixner <tglx@linutronix.de>

    upstream commit: 04e1b2e52b17195c9a1daa5935c55a4c8716095c

    We want to be a bit more clever in futex_lock_pi_atomic() and separate
    the possible states. Split out the code which attaches the first
    waiter to the owner into a separate function. No functional change.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Darren Hart <darren@dvhart.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Davidlohr Bueso <davidlohr@hp.com>
    Cc: Kees Cook <kees@outflux.net>
    Cc: wad@chromium.org
    Link: http://lkml.kernel.org/r/20140611204237.271300614@linutronix.de
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    ---
    kernel/futex.c | 42 ++++++++++++++++++++++++++++--------------
    1 file changed, 28 insertions(+), 14 deletions(-)

    diff --git a/kernel/futex.c b/kernel/futex.c
    index 8377eec3f650..e0802beff9ad 100644
    --- a/kernel/futex.c
    +++ b/kernel/futex.c
    @@ -855,21 +855,16 @@ out_state:
    return 0;
    }

    -static int
    -lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
    - union futex_key *key, struct futex_pi_state **ps)
    +/*
    + * Lookup the task for the TID provided from user space and attach to
    + * it after doing proper sanity checks.
    + */
    +static int attach_to_pi_owner(u32 uval, union futex_key *key,
    + struct futex_pi_state **ps)
    {
    - struct futex_q *match = futex_top_waiter(hb, key);
    - struct futex_pi_state *pi_state = NULL;
    - struct task_struct *p;
    pid_t pid = uval & FUTEX_TID_MASK;
    -
    - /*
    - * If there is a waiter on that futex, validate it and
    - * attach to the pi_state when the validation succeeds.
    - */
    - if (match)
    - return attach_to_pi_state(uval, match->pi_state, ps);
    + struct futex_pi_state *pi_state;
    + struct task_struct *p;

    /*
    * We are the first waiter - try to look up the real owner and attach
    @@ -912,7 +907,7 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
    pi_state = alloc_pi_state();

    /*
    - * Initialize the pi_mutex in locked state and make 'p'
    + * Initialize the pi_mutex in locked state and make @p
    * the owner of it:
    */
    rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
    @@ -932,6 +927,25 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
    return 0;
    }

    +static int lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
    + union futex_key *key, struct futex_pi_state **ps)
    +{
    + struct futex_q *match = futex_top_waiter(hb, key);
    +
    + /*
    + * If there is a waiter on that futex, validate it and
    + * attach to the pi_state when the validation succeeds.
    + */
    + if (match)
    + return attach_to_pi_state(uval, match->pi_state, ps);
    +
    + /*
    + * We are the first waiter - try to look up the owner based on
    + * @uval and attach to it.
    + */
    + return attach_to_pi_owner(uval, key, ps);
    +}
    +
    /**
    * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex
    * @uaddr: the pi futex user address
    --
    2.1.4



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