[PATCH] IRQ: prevent enabling of previously disabled interrupt
authorBryan Holty <lgeek@frontiernet.net>
Sat, 25 Mar 2006 11:07:37 +0000 (03:07 -0800)
committerLinus Torvalds <torvalds@g5.osdl.org>
Sat, 25 Mar 2006 16:22:55 +0000 (08:22 -0800)
commit501f2499b897ca4be68b1acc7a4bc8cf66f5fd24
tree279014a8fd8ce1ca43f036e416063e6a795e5889
parentc777ac5594f772ac760e02c3ac71d067616b579d
[PATCH] IRQ: prevent enabling of previously disabled interrupt

This fix prevents re-disabling and enabling of a previously disabled
interrupt.  On an SMP system with irq balancing enabled; If an interrupt is
disabled from within its own interrupt context with disable_irq_nosync and is
also earmarked for processor migration, the interrupt is blindly moved to the
other processor and enabled without regard for its current "enabled" state.
If there is an interrupt pending, it will unexpectedly invoke the irq handler
on the new irq owning processor (even though the irq was previously disabled)

The more intuitive fix would be to invoke disable_irq_nosync and
enable_irq, but since we already have the desc->lock from __do_IRQ, we
cannot call them directly.  Instead we can use the same logic to disable
and enable found in disable_irq_nosync and enable_irq, with regards to the
desc->depth.

This now prevents a disabled interrupt from being re-disabled, and more
importantly prevents a disabled interrupt from being incorrectly enabled on
a different processor.

Signed-off-by: Bryan Holty <lgeek@frontiernet.net>
Cc: Andi Kleen <ak@muc.de>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
kernel/irq/migration.c