acpi: fix bogus preemption logic
authorThomas Gleixner <tglx@linutronix.de>
Wed, 11 Aug 2010 21:17:29 +0000 (14:17 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 12 Aug 2010 15:43:29 +0000 (08:43 -0700)
commit0a7992c90828a65281c3c9cf180be3b432d277b2
tree41ecaca813576608b8eed10cabb9d8f3ab312dfa
parentd78a3eda6985e74bc21a23362f27526f73e71649
acpi: fix bogus preemption logic

The ACPI_PREEMPTION_POINT() logic was introduced in commit 8bd108d
(ACPICA: add preemption point after each opcode parse).  The follow up
commits abe1dfab6138d15692c084ca70 tried to fix the preemption logic
back and forth, but nobody noticed that the usage of
in_atomic_preempt_off() in that context is wrong.

The check which guards the call of cond_resched() is:

    if (!in_atomic_preempt_off() && !irqs_disabled())

in_atomic_preempt_off() is not intended for general use as the comment
above the macro definition clearly says:

 * Check whether we were atomic before we did preempt_disable():
 * (used by the scheduler, *after* releasing the kernel lock)

On a CONFIG_PREEMPT=n kernel the usage of in_atomic_preempt_off() works by
accident, but with CONFIG_PREEMPT=y it's just broken.

The whole purpose of the ACPI_PREEMPTION_POINT() is to reduce the latency
on a CONFIG_PREEMPT=n kernel, so make ACPI_PREEMPTION_POINT() depend on
CONFIG_PREEMPT=n and remove the in_atomic_preempt_off() check.

Addresses https://bugzilla.kernel.org/show_bug.cgi?id=16210

[akpm@linux-foundation.org: fix build]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Len Brown <lenb@kernel.org>
Cc: Francois Valenduc <francois.valenduc@tvcablenet.be>
Cc: Lin Ming <ming.m.lin@intel.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/acpi/apei/erst.c
include/acpi/platform/aclinux.h