tty: Only wakeup the line discipline idle queue when queue is active
Before waking up the tty line discipline idle queue first check if the queue is active (non empty). This prevents unnecessary entering the critical section in the wake_up() function and therefore avoid needless scheduling overhead on a PREEMPT_RT system caused by two processes being in the same critical section. Signed-off-by: Ivo Sieben <meltedpianoman@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -64,7 +64,9 @@ static void put_ldisc(struct tty_ldisc *ld)
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return;
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}
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raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
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wake_up(&ld->wq_idle);
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if (waitqueue_active(&ld->wq_idle))
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wake_up(&ld->wq_idle);
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}
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/**
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