Add IRQF_IRQPOLL flag (common code)

irqpoll is broken on some architectures that don't use the IRQ 0 for the timer
interrupt like IA64.  This patch adds a IRQF_IRQPOLL flag.

Each architecture is handled in a separate pach.  As I left the irq == 0 as
condition, this should not break existing architectures that use timer_irq ==
0 and that I did't address with that patch (because I don't know).

This patch:

This patch adds a IRQF_IRQPOLL flag that the interrupt registration code could
use for the interrupt it wants to use for IRQ polling.

Because this must not be the timer interrupt, an additional flag was added
instead of re-using the IRQF_TIMER constant.  Until all architectures will
have an IRQF_IRQPOLL interrupt, irq == 0 will stay as alternative as it should
not break anything.

Also, note_interrupt() is called on CPU-specific interrupts to be used as
interrupt source for IRQ polling.

Signed-off-by: Bernhard Walle <bwalle@suse.de>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Matthew Wilcox <willy@debian.org>
Cc: Grant Grundler <grundler@google.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/interrupt.h

@@ -44,6 +44,9 @@
  * IRQF_TIMER - Flag to mark this interrupt as timer interrupt
  * IRQF_PERCPU - Interrupt is per cpu
  * IRQF_NOBALANCING - Flag to exclude this interrupt from irq balancing
+ * IRQF_IRQPOLL - Interrupt is used for polling (only the interrupt that is
+ *                registered first in an shared interrupt is considered for
+ *                performance reasons)
  */
 #define IRQF_DISABLED		0x00000020
 #define IRQF_SAMPLE_RANDOM	0x00000040
@@ -52,6 +55,7 @@
 #define IRQF_TIMER		0x00000200
 #define IRQF_PERCPU		0x00000400
 #define IRQF_NOBALANCING	0x00000800
+#define IRQF_IRQPOLL		0x00001000
 
 /*
  * Migration helpers. Scheduled for removal in 9/2007

kernel/irq/handle.c

@@ -180,6 +180,8 @@ fastcall unsigned int __do_IRQ(unsigned int irq)
 		if (desc->chip->ack)
 			desc->chip->ack(irq);
 		action_ret = handle_IRQ_event(irq, desc->action);
+		if (!noirqdebug)
+			note_interrupt(irq, desc, action_ret);
 		desc->chip->end(irq);
 		return 1;
 	}

kernel/irq/spurious.c

@@ -146,7 +146,9 @@ void note_interrupt(unsigned int irq, struct irq_desc *desc,
 
 	if (unlikely(irqfixup)) {
 		/* Don't punish working computers */
-		if ((irqfixup == 2 && irq == 0) || action_ret == IRQ_NONE) {
+		if ((irqfixup == 2 && ((irq == 0) ||
+				(desc->action->flags & IRQF_IRQPOLL))) ||
+				action_ret == IRQ_NONE) {
 			int ok = misrouted_irq(irq);
 			if (action_ret == IRQ_NONE)
 				desc->irqs_unhandled -= ok;