There is an issue reported on imx6q restart function. The issue is only seen with the image building ARMv7 and ARMv6 together, where cpu_relax() is define to do dmb. It's been root-caused by Russell as below.
Russell King - ARM Linux wrote: > I suspect having this dmb inside cpu_relax() is flooding the > interconnects with traffic, which then prevents other CPUs getting > a look-in (maybe there's no fairness when it comes to dmb's. Fix the issue by insert a few NOPs into cpu_relax() where doing dmb. Cc: <[email protected]> Signed-off-by: Shawn Guo <[email protected]> --- arch/arm/include/asm/processor.h | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-) diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h index 99afa74..7cc67ce 100644 --- a/arch/arm/include/asm/processor.h +++ b/arch/arm/include/asm/processor.h @@ -80,7 +80,14 @@ extern void release_thread(struct task_struct *); unsigned long get_wchan(struct task_struct *p); #if __LINUX_ARM_ARCH__ == 6 || defined(CONFIG_ARM_ERRATA_754327) -#define cpu_relax() smp_mb() +#define cpu_relax() do { \ + asm("nop"); \ + asm("nop"); \ + asm("nop"); \ + asm("nop"); \ + asm("nop"); \ + smp_mb(); \ + } while (0) #else #define cpu_relax() barrier() #endif -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
