[patch 30/38] genirq: do not leave interupts enabled on free_irq

[Greg KH <gregkh@suse.de>]

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2.6.24-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Thomas Gleixner <tglx@linutronix.de>

commit 89d694b9dbe769ca1004e01db0ca43964806a611

The default_disable() function was changed in commit:

 76d2160147f43f982dfe881404cfde9fd0a9da21
 genirq: do not mask interrupts by default

It removed the mask function in favour of the default delayed
interrupt disabling. Unfortunately this also broke the shutdown in
free_irq() when the last handler is removed from the interrupt for
those architectures which rely on the default implementations. Now we
can end up with a enabled interrupt line after the last handler was
removed, which can result in spurious interrupts.

Fix this by adding a default_shutdown function, which is only
installed, when the irqchip implementation does provide neither a
shutdown nor a disable function.


Pointed-out-by: Michael Hennerich <Michael.Hennerich@analog.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Tested-by: Michael Hennerich <Michael.Hennerich@analog.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>


---
 kernel/irq/chip.c |   20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -246,6 +246,17 @@ static unsigned int default_startup(unsi
 }
 
 /*
+ * default shutdown function
+ */
+static void default_shutdown(unsigned int irq)
+{
+	struct irq_desc *desc = irq_desc + irq;
+
+	desc->chip->mask(irq);
+	desc->status |= IRQ_MASKED;
+}
+
+/*
  * Fixup enable/disable function pointers
  */
 void irq_chip_set_defaults(struct irq_chip *chip)
@@ -256,8 +267,15 @@ void irq_chip_set_defaults(struct irq_ch
 		chip->disable = default_disable;
 	if (!chip->startup)
 		chip->startup = default_startup;
+	/*
+	 * We use chip->disable, when the user provided its own. When
+	 * we have default_disable set for chip->disable, then we need
+	 * to use default_shutdown, otherwise the irq line is not
+	 * disabled on free_irq():
+	 */
 	if (!chip->shutdown)
-		chip->shutdown = chip->disable;
+		chip->shutdown = chip->disable != default_disable ?
+			chip->disable : default_shutdown;
 	if (!chip->name)
 		chip->name = chip->typename;
 	if (!chip->end)

--