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__do_IRQ does not check IRQ_DISABLED when IRQ_PER_CPU is set

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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 <[email protected]>
Cc: "Luck, Tony" <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Russ Anderson 2007-11-14 17:00:15 -08:00 • committed by Linus Torvalds
commit c642b8391c
1 changed files with 5 additions and 3 deletions
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8
kernel/irq/handle.c
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@ -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;
}