[PATCH 001/139] genirq: Avoid deadlock in spurious handling

From: Luis Henriques
Date: Thu Feb 28 2013 - 09:45:38 EST -stable review patch. If anyone has any objections, please let me know.


From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

commit e716efde75267eab919cdb2bef5b2cb77f305326 upstream.

commit 52553ddf(genirq: fix regression in irqfixup, irqpoll)
introduced a potential deadlock by calling the action handler with the
irq descriptor lock held.

Remove the call and let the handling code run even for an interrupt
where only a single action is registered. That matches the goal of
the above commit and avoids the deadlock.

Document the confusing action = desc->action reload in the handling
loop while at it.

Reported-and-tested-by: "Wang, Warner" <warner.wang@xxxxxx>
Tested-by: Edward Donovan <edward.donovan@xxxxxxxxxx>
Cc: "Wang, Song-Bo (Stoney)" <song-bo.wang@xxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
kernel/irq/spurious.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/irq/spurious.c b/kernel/irq/spurious.c
index 611cd60..7b5f012 100644
--- a/kernel/irq/spurious.c
+++ b/kernel/irq/spurious.c
@@ -80,13 +80,11 @@ static int try_one_irq(int irq, struct irq_desc *desc, bool force)

* All handlers must agree on IRQF_SHARED, so we test just the
- * first. Check for action->next as well.
+ * first.
action = desc->action;
if (!action || !(action->flags & IRQF_SHARED) ||
- (action->flags & __IRQF_TIMER) ||
- (action->handler(irq, action->dev_id) == IRQ_HANDLED) ||
- !action->next)
+ (action->flags & __IRQF_TIMER))
goto out;

/* Already running on another processor */
@@ -104,6 +102,7 @@ static int try_one_irq(int irq, struct irq_desc *desc, bool force)
do {
if (handle_irq_event(desc) == IRQ_HANDLED)
+ /* Make sure that there is still a valid action */
action = desc->action;
} while ((desc->istate & IRQS_PENDING) && action);
desc->istate &= ~IRQS_POLL_INPROGRESS;

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