Messages in this thread Patch in this message | | | From | Barry Song <> | Subject | [PATCH] Delete redundant IRQ_DISABLED check in irq_thread | Date | Fri, 17 Jul 2009 16:43:49 +0800 |
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Signed-off-by: Barry Song <21cnbao@gmail.com> I think it is completely redundant to check IRQ_DISABLED to decide whether thread_fn will be called.
At first, the irq_thread is waken up by HARDIRQ handler, if IRQ_DISABLED is true, HARDIRQ will have no chance to run, then irq_thread will not run. So there is only a situation that both HARDIRQ can run and IRQ_DISABLED is set. The case is that the flag is set in the interval of HARDIRQ enter and irq_thread is scheduled to run. I think there is nobody which is interested to disable irq in the interval except HARDIRQ handler itself. Then that causes the second problem I will explain.
Secondly, checking the flag causes some problems in fact. We often call disable_irq_nosync to diable irq in HARDIRQ to avoid flooding irq to follow. But the disable_irq_nosync will set IRQ_DISABLED flag, then that will prevent the execution of thread_fn. That's not the original idea to call disable_irq_nosync in HARDIRQ.
So I guess deleting the check is maybe better and more compact.
-Barry --- kernel/irq/manage.c | 17 +---------------- 1 files changed, 1 insertions(+), 16 deletions(-)
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index 50da676..ff4e05d 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -460,22 +460,7 @@ static int irq_thread(void *data) atomic_inc(&desc->threads_active); - spin_lock_irq(&desc->lock); - if (unlikely(desc->status & IRQ_DISABLED)) { - /* - * CHECKME: We might need a dedicated - * IRQ_THREAD_PENDING flag here, which - * retriggers the thread in check_irq_resend() - * but AFAICT IRQ_PENDING should be fine as it - * retriggers the interrupt itself --- tglx - */ - desc->status |= IRQ_PENDING; - spin_unlock_irq(&desc->lock); - } else { - spin_unlock_irq(&desc->lock); - - action->thread_fn(action->irq, action->dev_id); - } + action->thread_fn(action->irq, action->dev_id); wake = atomic_dec_and_test(&desc->threads_active); -- 1.5.6.3
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