[PATCH] Debug shared irqs

Drivers registering IRQ handlers with SA_SHIRQ really ought to be able to
handle an interrupt happening before request_irq() returns.  They also
ought to be able to handle an interrupt happening during the start of their
call to free_irq().  Let's test that hypothesis....

[bunk@stusta.de: Kconfig fixes]
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 356a5ab..63f04c1 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -77,6 +77,15 @@
 	  Say Y here if you are developing drivers or trying to debug and
 	  identify kernel problems.
 
+config DEBUG_SHIRQ
+	bool "Debug shared IRQ handlers"
+	depends on DEBUG_KERNEL && GENERIC_HARDIRQS
+	help
+	  Enable this to generate a spurious interrupt as soon as a shared
+	  interrupt handler is registered, and just before one is deregistered.
+	  Drivers ought to be able to handle interrupts coming in at those
+	  points; some don't and need to be caught.
+
 config LOG_BUF_SHIFT
 	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" if DEBUG_KERNEL
 	range 12 21