[lkml]   [2009]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH] Delete redundant IRQ_DISABLED check in irq_thread
Signed-off-by: Barry Song <>
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.

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)


- 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);


 \ /
  Last update: 2009-07-17 10:45    [W:0.052 / U:51.124 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site