diff options
| -rw-r--r-- | arch/x86/kernel/cpu/mtrr/main.c | 23 | ||||
| -rw-r--r-- | include/linux/stop_machine.h | 2 | ||||
| -rw-r--r-- | kernel/stop_machine.c | 2 |
3 files changed, 26 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c index 929739a..3d17bc7 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 } /** diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h index 092dc9b..14d3524 100644 --- a/include/linux/stop_machine.h +++ b/include/linux/stop_machine.h @@ -27,6 +27,8 @@ struct cpu_stop_work { struct cpu_stop_done *done; }; +extern struct mutex stop_cpus_mutex; + int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg); void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, struct cpu_stop_work *work_buf); diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index e3516b2..0cae1cc 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -132,8 +132,8 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), work_buf); } +DEFINE_MUTEX(stop_cpus_mutex); /* static data for stop_cpus */ -static DEFINE_MUTEX(stop_cpus_mutex); static DEFINE_PER_CPU(struct cpu_stop_work, stop_cpus_work); int __stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) |
