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    Subject[tip: irq/core] tasklets: Replace barrier() with cpu_relax() in tasklet_unlock_wait()
    The following commit has been merged into the irq/core branch of tip:

    Commit-ID: d2da74d1278a1b51ef18beafa9da770f0db1c617
    Gitweb: https://git.kernel.org/tip/d2da74d1278a1b51ef18beafa9da770f0db1c617
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Tue, 09 Mar 2021 09:42:04 +01:00
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitterDate: Wed, 17 Mar 2021 16:33:51 +01:00

    tasklets: Replace barrier() with cpu_relax() in tasklet_unlock_wait()

    A barrier() in a tight loop which waits for something to happen on a remote
    CPU is a pointless exercise. Replace it with cpu_relax() which allows HT
    siblings to make progress.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Link: https://lore.kernel.org/r/20210309084241.249343366@linutronix.de

    ---
    include/linux/interrupt.h | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
    index 2b98156..d689fd7 100644
    --- a/include/linux/interrupt.h
    +++ b/include/linux/interrupt.h
    @@ -672,7 +672,8 @@ static inline void tasklet_unlock(struct tasklet_struct *t)

    static inline void tasklet_unlock_wait(struct tasklet_struct *t)
    {
    - while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { barrier(); }
    + while (test_bit(TASKLET_STATE_RUN, &t->state))
    + cpu_relax();
    }
    #else
    #define tasklet_trylock(t) 1
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