[PATCH] ppc32: Don't synchronize in disable_irq() if no handler

This patch is the ppc32 counterpart to a fix that went into
arch/i386/kernel/irq.c last October.  The bug was noted by Al Viro: if
no handler exists, and we have IRQ_INPROGRESS set because of an
earlier irq that got through, synchronize_irq() will end up waiting
forever.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/ppc/kernel/irq.c

@@ -304,7 +304,9 @@ void disable_irq_nosync(unsigned int irq)
 
 void disable_irq(unsigned int irq)
 {
+	irq_desc_t *desc = irq_desc + irq;
 	disable_irq_nosync(irq);
+	if (desc->action)
 		synchronize_irq(irq);
 }