diff options
| -rw-r--r-- | arch/arm/kernel/smp.c | 42 |
1 files changed, 38 insertions, 4 deletions
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 1f2ccccaf009..4231034b8128 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -211,6 +211,13 @@ void __cpuinit __cpu_die(unsigned int cpu) } printk(KERN_NOTICE "CPU%u: shutdown\n", cpu); + /* + * platform_cpu_kill() is generally expected to do the powering off + * and/or cutting of clocks to the dying CPU. Optionally, this may + * be done by the CPU which is dying in preference to supporting + * this call, but that means there is _no_ synchronisation between + * the requesting CPU and the dying CPU actually losing power. + */ if (!platform_cpu_kill(cpu)) printk("CPU%u: unable to kill\n", cpu); } @@ -230,14 +237,41 @@ void __ref cpu_die(void) idle_task_exit(); local_irq_disable(); - mb(); - /* Tell __cpu_die() that this CPU is now safe to dispose of */ + /* + * Flush the data out of the L1 cache for this CPU. This must be + * before the completion to ensure that data is safely written out + * before platform_cpu_kill() gets called - which may disable + * *this* CPU and power down its cache. + */ + flush_cache_louis(); + + /* + * Tell __cpu_die() that this CPU is now safe to dispose of. Once + * this returns, power and/or clocks can be removed at any point + * from this CPU and its cache by platform_cpu_kill(). + */ RCU_NONIDLE(complete(&cpu_died)); /* - * actual CPU shutdown procedure is at least platform (if not - * CPU) specific. + * Ensure that the cache lines associated with that completion are + * written out. This covers the case where _this_ CPU is doing the + * powering down, to ensure that the completion is visible to the + * CPU waiting for this one. + */ + flush_cache_louis(); + + /* + * The actual CPU shutdown procedure is at least platform (if not + * CPU) specific. This may remove power, or it may simply spin. + * + * Platforms are generally expected *NOT* to return from this call, + * although there are some which do because they have no way to + * power down the CPU. These platforms are the _only_ reason we + * have a return path which uses the fragment of assembly below. + * + * The return path should not be used for platforms which can + * power off the CPU. */ if (smp_ops.cpu_die) smp_ops.cpu_die(cpu); |