genirq: Make irq_shutdown() symmetric vs. irq_startup again

If an irq_chip provides .irq_shutdown(), but neither of .irq_disable() or
.irq_mask(), free_irq() crashes when jumping to NULL.
Fix this by only trying .irq_disable() and .irq_mask() if there's no
.irq_shutdown() provided.

This revives the symmetry with irq_startup(), which tries .irq_startup(),
.irq_enable(), and irq_unmask(), and makes it consistent with the comment for
irq_chip.irq_shutdown() in <linux/irq.h>, which says:

 * @irq_shutdown:	shut down the interrupt (defaults to ->disable if NULL)

This is also how __free_irq() behaved before the big overhaul, cfr. e.g.
3b56f0585fd4c02d047dc406668cb40159b2d340 ("genirq: Remove bogus conditional"),
where the core interrupt code always overrode .irq_shutdown() to
.irq_disable() if .irq_shutdown() was NULL.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-m68k@lists.linux-m68k.org
Link: http://lkml.kernel.org/r/1315742394-16036-2-git-send-email-geert@linux-m68k.org
Cc: stable@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index d5a3009..dc5114b 100644 (file)
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -178,7 +178,7 @@ void irq_shutdown(struct irq_desc *desc)
        desc->depth = 1;
        if (desc->irq_data.chip->irq_shutdown)
                desc->irq_data.chip->irq_shutdown(&desc->irq_data);
-       if (desc->irq_data.chip->irq_disable)
+       else if (desc->irq_data.chip->irq_disable)
                desc->irq_data.chip->irq_disable(&desc->irq_data);
        else
                desc->irq_data.chip->irq_mask(&desc->irq_data);