diff options
| -rw-r--r-- | arch/x86/kernel/cpu/mtrr/main.c | 192 | ||||
| -rw-r--r-- | include/linux/stop_machine.h | 2 | ||||
| -rw-r--r-- | kernel/stop_machine.c | 2 |
3 files changed, 42 insertions, 154 deletions
diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c index 3d17bc7f06e6..707b6377adf1 100644 --- a/arch/x86/kernel/cpu/mtrr/main.c +++ b/arch/x86/kernel/cpu/mtrr/main.c @@ -137,55 +137,43 @@ static void __init init_table(void) } struct set_mtrr_data { - atomic_t count; - atomic_t gate; unsigned long smp_base; unsigned long smp_size; unsigned int smp_reg; mtrr_type smp_type; }; -static DEFINE_PER_CPU(struct cpu_stop_work, mtrr_work); - /** - * mtrr_work_handler - Synchronisation handler. Executed by "other" CPUs. + * mtrr_rendezvous_handler - Work done in the synchronization handler. Executed + * by all the CPUs. * @info: pointer to mtrr configuration data * * Returns nothing. */ -static int mtrr_work_handler(void *info) +static int mtrr_rendezvous_handler(void *info) { #ifdef CONFIG_SMP struct set_mtrr_data *data = info; - unsigned long flags; - - atomic_dec(&data->count); - while (!atomic_read(&data->gate)) - cpu_relax(); - - local_irq_save(flags); - - atomic_dec(&data->count); - while (atomic_read(&data->gate)) - cpu_relax(); - /* The master has cleared me to execute */ + /* + * We use this same function to initialize the mtrrs during boot, + * resume, runtime cpu online and on an explicit request to set a + * specific MTRR. + * + * During boot or suspend, the state of the boot cpu's mtrrs has been + * saved, and we want to replicate that across all the cpus that come + * online (either at the end of boot or resume or during a runtime cpu + * online). If we're doing that, @reg is set to something special and on + * all the cpu's we do mtrr_if->set_all() (On the logical cpu that + * started the boot/resume sequence, this might be a duplicate + * set_all()). + */ if (data->smp_reg != ~0U) { mtrr_if->set(data->smp_reg, data->smp_base, data->smp_size, data->smp_type); - } else if (mtrr_aps_delayed_init) { - /* - * Initialize the MTRRs inaddition to the synchronisation. - */ + } else if (mtrr_aps_delayed_init || !cpu_online(smp_processor_id())) { mtrr_if->set_all(); } - - atomic_dec(&data->count); - while (!atomic_read(&data->gate)) - cpu_relax(); - - atomic_dec(&data->count); - local_irq_restore(flags); #endif return 0; } @@ -223,20 +211,11 @@ static inline int types_compatible(mtrr_type type1, mtrr_type type2) * 14. Wait for buddies to catch up * 15. Enable interrupts. * - * What does that mean for us? Well, first we set data.count to the number - * of CPUs. As each CPU announces that it started the rendezvous handler by - * decrementing the count, We reset data.count and set the data.gate flag - * allowing all the cpu's to proceed with the work. As each cpu disables - * interrupts, it'll decrement data.count once. We wait until it hits 0 and - * proceed. We clear the data.gate flag and reset data.count. Meanwhile, they - * are waiting for that flag to be cleared. Once it's cleared, each - * CPU goes through the transition of updating MTRRs. - * The CPU vendors may each do it differently, - * so we call mtrr_if->set() callback and let them take care of it. - * When they're done, they again decrement data->count and wait for data.gate - * to be set. - * When we finish, we wait for data.count to hit 0 and toggle the data.gate flag - * Everyone then enables interrupts and we all continue on. + * What does that mean for us? Well, stop_machine() will ensure that + * the rendezvous handler is started on each CPU. And in lockstep they + * do the state transition of disabling interrupts, updating MTRR's + * (the CPU vendors may each do it differently, so we call mtrr_if->set() + * callback and let them take care of it.) and enabling interrupts. * * Note that the mechanism is the same for UP systems, too; all the SMP stuff * becomes nops. @@ -244,115 +223,26 @@ static inline int types_compatible(mtrr_type type1, mtrr_type type2) static void set_mtrr(unsigned int reg, unsigned long base, unsigned long size, mtrr_type type) { - struct set_mtrr_data data; - 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; - data.smp_base = base; - data.smp_size = size; - data.smp_type = type; - atomic_set(&data.count, num_booting_cpus() - 1); - - /* Make sure data.count is visible before unleashing other CPUs */ - smp_wmb(); - atomic_set(&data.gate, 0); - - /* Start the ball rolling on other CPUs */ - for_each_online_cpu(cpu) { - struct cpu_stop_work *work = &per_cpu(mtrr_work, cpu); - - if (cpu == smp_processor_id()) - continue; + struct set_mtrr_data data = { .smp_reg = reg, + .smp_base = base, + .smp_size = size, + .smp_type = type + }; - stop_one_cpu_nowait(cpu, mtrr_work_handler, &data, work); - } - - - while (atomic_read(&data.count)) - cpu_relax(); - - /* Ok, reset count and toggle gate */ - atomic_set(&data.count, num_booting_cpus() - 1); - smp_wmb(); - atomic_set(&data.gate, 1); - - local_irq_save(flags); - - while (atomic_read(&data.count)) - cpu_relax(); - - /* Ok, reset count and toggle gate */ - atomic_set(&data.count, num_booting_cpus() - 1); - smp_wmb(); - atomic_set(&data.gate, 0); - - /* Do our MTRR business */ - - /* - * HACK! - * - * We use this same function to initialize the mtrrs during boot, - * resume, runtime cpu online and on an explicit request to set a - * specific MTRR. - * - * During boot or suspend, the state of the boot cpu's mtrrs has been - * saved, and we want to replicate that across all the cpus that come - * online (either at the end of boot or resume or during a runtime cpu - * online). If we're doing that, @reg is set to something special and on - * this cpu we still do mtrr_if->set_all(). During boot/resume, this - * is unnecessary if at this point we are still on the cpu that started - * the boot/resume sequence. But there is no guarantee that we are still - * on the same cpu. So we do mtrr_if->set_all() on this cpu aswell to be - * sure that we are in sync with everyone else. - */ - if (reg != ~0U) - mtrr_if->set(reg, base, size, type); - else - mtrr_if->set_all(); - - /* Wait for the others */ - while (atomic_read(&data.count)) - cpu_relax(); - - atomic_set(&data.count, num_booting_cpus() - 1); - smp_wmb(); - atomic_set(&data.gate, 1); - - /* - * Wait here for everyone to have seen the gate change - * So we're the last ones to touch 'data' - */ - while (atomic_read(&data.count)) - cpu_relax(); + stop_machine(mtrr_rendezvous_handler, &data, cpu_online_mask); +} - local_irq_restore(flags); - preempt_enable(); -#ifdef CONFIG_SMP - if (cpu_active(raw_smp_processor_id())) - mutex_unlock(&stop_cpus_mutex); -#endif +static void set_mtrr_from_inactive_cpu(unsigned int reg, unsigned long base, + unsigned long size, mtrr_type type) +{ + struct set_mtrr_data data = { .smp_reg = reg, + .smp_base = base, + .smp_size = size, + .smp_type = type + }; + + stop_machine_from_inactive_cpu(mtrr_rendezvous_handler, &data, + cpu_callout_mask); } /** @@ -806,7 +696,7 @@ void mtrr_ap_init(void) * 2. cpu hotadd time. We let mtrr_add/del_page hold cpuhotplug * lock to prevent mtrr entry changes */ - set_mtrr(~0U, 0, 0, 0); + set_mtrr_from_inactive_cpu(~0U, 0, 0, 0); } /** diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h index e0f2da25d751..4a9d0c7edc65 100644 --- a/include/linux/stop_machine.h +++ b/include/linux/stop_machine.h @@ -27,8 +27,6 @@ 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 e8f05b14cd43..c1124752e1d3 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); static void queue_stop_cpus_work(const struct cpumask *cpumask, |