The patch titled
__do_IRQ does not check IRQ_DISABLED when IRQ_PER_CPU is set
has been added to the -mm tree. Its filename is
__do_irq-does-not-check-irq_disabled-when-irq_per_cpu-is-set.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: __do_IRQ does not check IRQ_DISABLED when IRQ_PER_CPU is set
From: Russ Anderson <rja@xxxxxxx>
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 <rja@xxxxxxx>
Cc: "Luck, Tony" <tony.luck@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Bjorn Helgaas <bjorn.helgaas@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/irq/handle.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff -puN kernel/irq/handle.c~__do_irq-does-not-check-irq_disabled-when-irq_per_cpu-is-set kernel/irq/handle.c
--- a/kernel/irq/handle.c~__do_irq-does-not-check-irq_disabled-when-irq_per_cpu-is-set
+++ a/kernel/irq/handle.c
@@ -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;
}
_
Patches currently in -mm which might be from rja@xxxxxxx are
arch-ia64-sn-kernel-mcac-undo-lock-when-sn_oemdata-cant-be-extended.patch
__do_irq-does-not-check-irq_disabled-when-irq_per_cpu-is-set.patch
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