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    SubjectRe: [PATCH]: use spin_lock_irqsave in try_one_irq()
    From
    > 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@redhat.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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