From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russ Anderson Date: Tue, 30 Oct 2007 16:26:57 +0000 Subject: [patch] __do_IRQ does not check IRQ_DISABLED when IRQ_PER_CPU is set Message-Id: <20071030162657.GA21728@sgi.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: LKML , akpm@linux-foundation.org, linux-ia64@vger.kernel.org [patch] __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. Comments??? Signed-off-by: Russ Anderson (rja@sgi.com) -------------------------------------------------------------------- --- kernel/irq/handle.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) Index: linus/kernel/irq/handle.c =================================--- linus.orig/kernel/irq/handle.c 2007-10-30 09:49:26.000000000 -0500 +++ linus/kernel/irq/handle.c 2007-10-30 10:23:52.436719688 -0500 @@ -178,9 +178,11 @@ fastcall unsigned int __do_IRQ(unsigned */ 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; } -- Russ Anderson, OS RAS/Partitioning Project Lead SGI - Silicon Graphics Inc rja@sgi.com