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Subject[PATCH] Delete redundant IRQ_DISABLED check in irq_thread
Date
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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