diff options
| author | Will Deacon <will.deacon@arm.com> | 2011-03-04 12:38:54 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2011-03-09 21:40:18 +0000 |
| commit | 5dab26af1bacad9a7189d904fbc8b4fe8e95dd81 (patch) | |
| tree | 246c70038035ee4a0505f2b043ecb3c73018b01b | |
| parent | fcbdc5fe6ebe07d502c9b652cb63376bcc4227ac (diff) | |
ARM: 6784/1: errata: no automatic Store Buffer drain on Cortex-A9
On revisions of the Cortex-A9 prior to r2p0, the Store Buffer does not
have any automatic draining mechanism and therefore a livelock may occur
if an external agent continuously polls a memory location waiting to
observe an update.
This workaround defines cpu_relax() as smp_mb(), preventing correctly
written polling loops from denying visibility of updates to memory.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
| -rw-r--r-- | arch/arm/Kconfig | 11 | ||||
| -rw-r--r-- | arch/arm/include/asm/processor.h | 2 |
2 files changed, 12 insertions, 1 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index ec0f6589af05..d3f2de37a4b7 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1213,6 +1213,17 @@ config ARM_ERRATA_754322 the new ASID. This workaround places two dsb instructions in the mm switching code so that no page table walks can cross the ASID switch. +config ARM_ERRATA_754327 + bool "ARM errata: no automatic Store Buffer drain" + depends on CPU_V7 && SMP + help + This option enables the workaround for the 754327 Cortex-A9 (prior to + r2p0) erratum. The Store Buffer does not have any automatic draining + mechanism and therefore a livelock may occur if an external agent + continuously polls a memory location waiting to observe an update. + This workaround defines cpu_relax() as smp_mb(), preventing correctly + written polling loops from denying visibility of updates to memory. + endmenu source "arch/arm/common/Kconfig" diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h index 67357baaeeeb..7a1f03c10f1b 100644 --- a/arch/arm/include/asm/processor.h +++ b/arch/arm/include/asm/processor.h @@ -95,7 +95,7 @@ extern void release_thread(struct task_struct *); unsigned long get_wchan(struct task_struct *p); -#if __LINUX_ARM_ARCH__ == 6 +#if __LINUX_ARM_ARCH__ == 6 || defined(CONFIG_ARM_ERRATA_754327) #define cpu_relax() smp_mb() #else #define cpu_relax() barrier() |