irq: provide debug_poll_all_shared_irqs() method under CONFIG_DEBUG_SHIRQ

Provide a shared interrupt debug facility under CONFIG_DEBUG_SHIRQ:
it uses the existing irqpoll facilities to iterate through all
registered interrupt handlers and call those which can handle shared
IRQ lines.

This can be handy for suspend/resume debugging: if we call this function
early during resume we can trigger crashes in those drivers which have
incorrect assumptions about when exactly their ISRs will be called
during suspend/resume.
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/interrupt.h

@@ -462,6 +462,12 @@ static inline void init_irq_proc(void)
 }
 #endif
 
+#if defined(CONFIG_GENERIC_HARDIRQS) && defined(CONFIG_DEBUG_SHIRQ)
+extern void debug_poll_all_shared_irqs(void);
+#else
+static inline void debug_poll_all_shared_irqs(void) { }
+#endif
+
 int show_interrupts(struct seq_file *p, void *v);
 
 struct irq_desc;

kernel/irq/spurious.c

@@ -104,7 +104,7 @@ static int misrouted_irq(int irq)
 	return ok;
 }
 
-static void poll_spurious_irqs(unsigned long dummy)
+static void poll_all_shared_irqs(void)
 {
 	struct irq_desc *desc;
 	int i;
@@ -123,11 +123,23 @@ static void poll_spurious_irqs(unsigned long dummy)
 
 		try_one_irq(i, desc);
 	}
+}
+
+static void poll_spurious_irqs(unsigned long dummy)
+{
+	poll_all_shared_irqs();
 
 	mod_timer(&poll_spurious_irq_timer,
 		  jiffies + POLL_SPURIOUS_IRQ_INTERVAL);
 }
 
+#ifdef CONFIG_DEBUG_SHIRQ
+void debug_poll_all_shared_irqs(void)
+{
+	poll_all_shared_irqs();
+}
+#endif
+
 /*
  * If 99,900 of the previous 100,000 interrupts have not been handled
  * then assume that the IRQ is stuck in some manner. Drop a diagnostic