diff options
Diffstat (limited to 'kernel/cpu.c')
| -rw-r--r-- | kernel/cpu.c | 145 |
1 files changed, 144 insertions, 1 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 9572ca043727..9048c33689ac 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -22,6 +22,7 @@ #include <linux/lockdep.h> #include <linux/tick.h> #include <linux/irq.h> +#include <linux/smpboot.h> #include <trace/events/power.h> #define CREATE_TRACE_POINTS @@ -33,10 +34,24 @@ * cpuhp_cpu_state - Per cpu hotplug state storage * @state: The current cpu state * @target: The target state + * @thread: Pointer to the hotplug thread + * @should_run: Thread should execute + * @cb_stat: The state for a single callback (install/uninstall) + * @cb: Single callback function (install/uninstall) + * @result: Result of the operation + * @done: Signal completion to the issuer of the task */ struct cpuhp_cpu_state { enum cpuhp_state state; enum cpuhp_state target; +#ifdef CONFIG_SMP + struct task_struct *thread; + bool should_run; + enum cpuhp_state cb_state; + int (*cb)(unsigned int cpu); + int result; + struct completion done; +#endif }; static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state); @@ -394,6 +409,134 @@ static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st, return ret; } +/* + * The cpu hotplug threads manage the bringup and teardown of the cpus + */ +static void cpuhp_create(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + + init_completion(&st->done); +} + +static int cpuhp_should_run(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); + + return st->should_run; +} + +/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */ +static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st) +{ + enum cpuhp_state target = max((int)st->target, CPUHP_AP_ONLINE); + + return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target); +} + +/* Execute the online startup callbacks. Used to be CPU_ONLINE */ +static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st) +{ + return cpuhp_up_callbacks(cpu, st, cpuhp_ap_states, st->target); +} + +/* + * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke + * callbacks when a state gets [un]installed at runtime. + */ +static void cpuhp_thread_fun(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); + int ret = 0; + + /* + * Paired with the mb() in cpuhp_kick_ap_work and + * cpuhp_invoke_ap_callback, so the work set is consistent visible. + */ + smp_mb(); + if (!st->should_run) + return; + + st->should_run = false; + + /* Single callback invocation for [un]install ? */ + if (st->cb) { + if (st->cb_state < CPUHP_AP_ONLINE) { + local_irq_disable(); + ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb); + local_irq_enable(); + } else { + ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb); + } + } else { + /* Regular hotplug work */ + if (st->state < st->target) + ret = cpuhp_ap_online(cpu, st); + else if (st->state > st->target) + ret = cpuhp_ap_offline(cpu, st); + } + st->result = ret; + complete(&st->done); +} + +/* Invoke a single callback on a remote cpu */ +static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, + int (*cb)(unsigned int)) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + + if (!cpu_online(cpu)) + return 0; + + st->cb_state = state; + st->cb = cb; + /* + * Make sure the above stores are visible before should_run becomes + * true. Paired with the mb() above in cpuhp_thread_fun() + */ + smp_mb(); + st->should_run = true; + wake_up_process(st->thread); + wait_for_completion(&st->done); + return st->result; +} + +/* Regular hotplug invocation of the AP hotplug thread */ +static int cpuhp_kick_ap_work(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + enum cpuhp_state state = st->state; + + trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work); + st->result = 0; + st->cb = NULL; + /* + * Make sure the above stores are visible before should_run becomes + * true. Paired with the mb() above in cpuhp_thread_fun() + */ + smp_mb(); + st->should_run = true; + wake_up_process(st->thread); + wait_for_completion(&st->done); + trace_cpuhp_exit(cpu, st->state, state, st->result); + return st->result; +} + +static struct smp_hotplug_thread cpuhp_threads = { + .store = &cpuhp_state.thread, + .create = &cpuhp_create, + .thread_should_run = cpuhp_should_run, + .thread_fn = cpuhp_thread_fun, + .thread_comm = "cpuhp/%u", + .selfparking = true, +}; + +void __init cpuhp_threads_init(void) +{ + BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads)); + kthread_unpark(this_cpu_read(cpuhp_state.thread)); +} + #ifdef CONFIG_HOTPLUG_CPU EXPORT_SYMBOL(register_cpu_notifier); EXPORT_SYMBOL(__register_cpu_notifier); @@ -997,7 +1140,7 @@ static int cpuhp_cb_check(enum cpuhp_state state) static bool cpuhp_is_ap_state(enum cpuhp_state state) { - return (state > CPUHP_AP_OFFLINE && state < CPUHP_AP_ONLINE); + return (state >= CPUHP_AP_OFFLINE && state <= CPUHP_AP_ONLINE); } static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state) |