From c642b8391cf8efc3622cc97329a0f46e7cbb70b8 Mon Sep 17 00:00:00 2001 From: Russ Anderson Date: Wed, 14 Nov 2007 17:00:15 -0800 Subject: __do_IRQ does not check IRQ_DISABLED when IRQ_PER_CPU is set In __do_IRQ(), the normal case is that IRQ_DISABLED is checked and if set the handler (handle_IRQ_event()) is not called. Earlier in __do_IRQ(), if IRQ_PER_CPU is set the code does not check IRQ_DISABLED and calls the handler even though IRQ_DISABLED is set. This behavior seems unintentional. One user encountering this behavior is the CPE handler (in arch/ia64/kernel/mca.c). When the CPE handler encounters too many CPEs (such as a solid single bit error), it sets up a polling timer and disables the CPE interrupt (to avoid excessive overhead logging the stream of single bit errors). disable_irq_nosync() is called which sets IRQ_DISABLED. The IRQ_PER_CPU flag was previously set (in ia64_mca_late_init()). The net result is the CPE handler gets called even though it is marked disabled. If the behavior of not checking IRQ_DISABLED when IRQ_PER_CPU is set is intentional, it would be worthy of a comment describing the intended behavior. disable_irq_nosync() does call chip->disable() to provide a chipset specifiec interface for disabling the interrupt, which avoids this issue when used. Signed-off-by: Russ Anderson Cc: "Luck, Tony" Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Bjorn Helgaas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/irq/handle.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c index e391cbb1f56..dc335ad2752 100644 --- a/kernel/irq/handle.c +++ b/kernel/irq/handle.c @@ -178,9 +178,11 @@ 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); + if (likely(!(desc->status & IRQ_DISABLED))) { + action_ret = handle_IRQ_event(irq, desc->action); + if (!noirqdebug) + note_interrupt(irq, desc, action_ret); + } desc->chip->end(irq); return 1; } -- cgit v1.2.3