On Tue, 30 Oct 2007 11:26:57 -0500 Russ Anderson <rja@xxxxxxx> wrote: > [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??? > It looks right to me. > > -------------------------------------------------------------------- > --- > 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; > } Alas, I can't remember who wrote (and cares about) the IRQ_PER_CPU support. Oh well. - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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