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Message-ID: <2674af740911030658m76b702cfxb67723984286c4bb@mail.gmail.com>
Date: Tue, 3 Nov 2009 22:58:54 +0800
From: Yong Zhang <yong.zhang0@...il.com>
To: Prarit Bhargava <prarit@...hat.com>
Cc: linux-kernel@...r.kernel.org, ebiederm@...ssion.com,
akpm@...ux-foundation.org, Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH]: use spin_lock_irqsave in try_one_irq()
> This happens because the &desc->lock is taken with spin_lock_irqsave and
> just a spin_lock. In the try_one_irq(), this lock really should be a
> spin_lock_irqsave().
>
Cc'ed Ingo and Thomas.
The reason is that try_one_irq() is called both from hardirq context and softirq
context. And by default the timer handler poll_all_shared_irqs() is
called with irq enabled.
Then the two usage will cause inconsistent.
So I think the following patch is also workable to you.
diff --git a/kernel/irq/spurious.c b/kernel/irq/spurious.c
index 114e704..11affbc 100644
--- a/kernel/irq/spurious.c
+++ b/kernel/irq/spurious.c
@@ -111,6 +111,7 @@ static void poll_all_shared_irqs(void)
for_each_irq_desc(i, desc) {
unsigned int status;
+ unsigned long flags;
if (!i)
continue;
@@ -121,7 +122,9 @@ static void poll_all_shared_irqs(void)
if (!(status & IRQ_SPURIOUS_DISABLED))
continue;
+ local_irq_save(flags);
try_one_irq(i, desc);
+ local_irq_restore(flags);
}
}
> I have not yet narrowed down the reason for the spurious interrupt (although
> I suspect it maybe to do with the radeon driver).
>
> Successfully tested by me.
>
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
>
> --- linux-2.6.31.x86_64.orig/kernel/irq/spurious.c 2009-09-09 18:13:59.000000000 -0400
> +++ linux-2.6.31.x86_64/kernel/irq/spurious.c 2009-10-26 10:55:56.709845786 -0400
> @@ -27,8 +27,9 @@ static int try_one_irq(int irq, struct i
> {
> struct irqaction *action;
> int ok = 0, work = 0;
> + unsigned long flags;
>
> - spin_lock(&desc->lock);
> + spin_lock_irqsave(&desc->lock, flags);
> /* Already running on another processor */
> if (desc->status & IRQ_INPROGRESS) {
> /*
> @@ -37,13 +38,13 @@ static int try_one_irq(int irq, struct i
> */
> if (desc->action && (desc->action->flags & IRQF_SHARED))
> desc->status |= IRQ_PENDING;
> - spin_unlock(&desc->lock);
> + spin_unlock_irqrestore(&desc->lock, flags);
> return ok;
> }
> /* Honour the normal IRQ locking */
> desc->status |= IRQ_INPROGRESS;
> action = desc->action;
> - spin_unlock(&desc->lock);
> + spin_unlock_irqrestore(&desc->lock, flags);
>
> while (action) {
> /* Only shared IRQ handlers are safe to call */
> @@ -56,7 +57,7 @@ static int try_one_irq(int irq, struct i
> }
> local_irq_disable();
> /* Now clean up the flags */
> - spin_lock(&desc->lock);
> + spin_lock_irqsave(&desc->lock, flags);
> action = desc->action;
>
> /*
> @@ -68,9 +69,9 @@ static int try_one_irq(int irq, struct i
> * Perform real IRQ processing for the IRQ we deferred
> */
> work = 1;
> - spin_unlock(&desc->lock);
> + spin_unlock_irqrestore(&desc->lock, flags);
> handle_IRQ_event(irq, action);
> - spin_lock(&desc->lock);
> + spin_lock_irqsave(&desc->lock, flags);
> desc->status &= ~IRQ_PENDING;
> }
> desc->status &= ~IRQ_INPROGRESS;
> @@ -80,7 +81,7 @@ static int try_one_irq(int irq, struct i
> */
> if (work && desc->chip && desc->chip->end)
> desc->chip->end(irq);
> - spin_unlock(&desc->lock);
> + spin_unlock_irqrestore(&desc->lock, flags);
>
> return ok;
> }
> --
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