diff options
Diffstat (limited to 'arch/x86/kernel/cpu/mtrr/main.c')
| -rw-r--r-- | arch/x86/kernel/cpu/mtrr/main.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c index 929739a653d..3d17bc7f06e 100644 --- a/arch/x86/kernel/cpu/mtrr/main.c +++ b/arch/x86/kernel/cpu/mtrr/main.c @@ -248,6 +248,25 @@ set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type typ unsigned long flags; int cpu; +#ifdef CONFIG_SMP + /* + * If this cpu is not yet active, we are in the cpu online path. There + * can be no stop_machine() in parallel, as stop machine ensures this + * by using get_online_cpus(). We can skip taking the stop_cpus_mutex, + * as we don't need it and also we can't afford to block while waiting + * for the mutex. + * + * If this cpu is active, we need to prevent stop_machine() happening + * in parallel by taking the stop cpus mutex. + * + * Also, this is called in the context of cpu online path or in the + * context where cpu hotplug is prevented. So checking the active status + * of the raw_smp_processor_id() is safe. + */ + if (cpu_active(raw_smp_processor_id())) + mutex_lock(&stop_cpus_mutex); +#endif + preempt_disable(); data.smp_reg = reg; @@ -330,6 +349,10 @@ set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type typ local_irq_restore(flags); preempt_enable(); +#ifdef CONFIG_SMP + if (cpu_active(raw_smp_processor_id())) + mutex_unlock(&stop_cpus_mutex); +#endif } /** |