From 0a7992c90828a65281c3c9cf180be3b432d277b2 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 11 Aug 2010 14:17:29 -0700 Subject: [PATCH] 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 abe1dfab6, 138d15692, c084ca70 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 Cc: Len Brown Cc: Francois Valenduc Cc: Lin Ming Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/acpi/apei/erst.c | 1 + include/acpi/platform/aclinux.h | 10 +++++++--- 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c index 864dd46c346f..18645f4e83cd 100644 --- a/drivers/acpi/apei/erst.c +++ b/drivers/acpi/apei/erst.c @@ -33,6 +33,7 @@ #include #include #include +#include #include #include "apei-internal.h" diff --git a/include/acpi/platform/aclinux.h b/include/acpi/platform/aclinux.h index e5039a2856f8..103f08aca764 100644 --- a/include/acpi/platform/aclinux.h +++ b/include/acpi/platform/aclinux.h @@ -148,13 +148,17 @@ static inline void *acpi_os_acquire_object(acpi_cache_t * cache) #define ACPI_ALLOCATE_ZEROED(a) acpi_os_allocate_zeroed(a) #define ACPI_FREE(a) kfree(a) -/* Used within ACPICA to show where it is safe to preempt execution */ -#include +#ifndef CONFIG_PREEMPT +/* + * Used within ACPICA to show where it is safe to preempt execution + * when CONFIG_PREEMPT=n + */ #define ACPI_PREEMPTION_POINT() \ do { \ - if (!in_atomic_preempt_off() && !irqs_disabled()) \ + if (!irqs_disabled()) \ cond_resched(); \ } while (0) +#endif #endif /* __KERNEL__ */ -- 2.30.2