[PATCH v2] irq: Guard handle_bad_irq log messages

[Guenter Roeck <linux@roeck-us.net>]

An interrupt storm on a bad interrupt will cause the kernel
log to be clogged.

[   60.089234] ->handle_irq():  ffffffffbe2f803f,
[   60.090455] 0xffffffffbf2af380
[   60.090510] handle_bad_irq+0x0/0x2e5
[   60.090522] ->irq_data.chip(): ffffffffbf2af380,
[   60.090553]    IRQ_NOPROBE set
[   60.090584] ->handle_irq():  ffffffffbe2f803f,
[   60.090590] handle_bad_irq+0x0/0x2e5
[   60.090596] ->irq_data.chip(): ffffffffbf2af380,
[   60.090602] 0xffffffffbf2af380
[   60.090608] ->action():           (null)
[   60.090779] handle_bad_irq+0x0/0x2e5

This was seen when running an upstream kernel on Acer Chromebook R11.
The system was unstable as result.

Guard the log message with __printk_ratelimit to reduce the impact.
This won't prevent the interrupt storm from happening, but at least
the system remains stable.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=197953
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Dmitry Torokhov <dtor@chromium.org>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Move rate limiting into print_irq_desc()

 kernel/irq/debug.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/irq/debug.h b/kernel/irq/debug.h
index 17f05ef8f575..e4d3819a91cc 100644
--- a/kernel/irq/debug.h
+++ b/kernel/irq/debug.h
@@ -12,6 +12,11 @@
 
 static inline void print_irq_desc(unsigned int irq, struct irq_desc *desc)
 {
+	static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 5);
+
+	if (!__ratelimit(&ratelimit))
+		return;
+
 	printk("irq %d, desc: %p, depth: %d, count: %d, unhandled: %d\n",
 		irq, desc, desc->depth, desc->irq_count, desc->irqs_unhandled);
 	printk("->handle_irq():  %p, ", desc->handle_irq);
-- 
2.7.4