X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=kernel%2Fcpu.c;h=6ea42e8da861b05077d01a23e15bb140afffa605;hb=1dcaac1ce07db672e2cb5b4ef9642990689bb2a1;hp=b5eacb9587af23bef245c801ef6a67eb2b7332fc;hpb=5b7aa87e0482be768486e0c2277aa4122487eb9d;p=deliverable%2Flinux.git diff --git a/kernel/cpu.c b/kernel/cpu.c index b5eacb9587af..6ea42e8da861 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #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); @@ -314,6 +329,14 @@ static int notify_starting(unsigned int cpu) return 0; } +static int bringup_wait_for_ap(unsigned int cpu) +{ + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); + + wait_for_completion(&st->done); + return st->result; +} + static int bringup_cpu(unsigned int cpu) { struct task_struct *idle = idle_thread_get(cpu); @@ -325,14 +348,215 @@ static int bringup_cpu(unsigned int cpu) cpu_notify(CPU_UP_CANCELED, cpu); return ret; } + ret = bringup_wait_for_ap(cpu); BUG_ON(!cpu_online(cpu)); - return 0; + return ret; +} + +/* + * Hotplug state machine related functions + */ +static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st, + struct cpuhp_step *steps) +{ + for (st->state++; st->state < st->target; st->state++) { + struct cpuhp_step *step = steps + st->state; + + if (!step->skip_onerr) + cpuhp_invoke_callback(cpu, st->state, step->startup); + } +} + +static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st, + struct cpuhp_step *steps, enum cpuhp_state target) +{ + enum cpuhp_state prev_state = st->state; + int ret = 0; + + for (; st->state > target; st->state--) { + struct cpuhp_step *step = steps + st->state; + + ret = cpuhp_invoke_callback(cpu, st->state, step->teardown); + if (ret) { + st->target = prev_state; + undo_cpu_down(cpu, st, steps); + break; + } + } + return ret; +} + +static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st, + struct cpuhp_step *steps) +{ + for (st->state--; st->state > st->target; st->state--) { + struct cpuhp_step *step = steps + st->state; + + if (!step->skip_onerr) + cpuhp_invoke_callback(cpu, st->state, step->teardown); + } +} + +static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st, + struct cpuhp_step *steps, enum cpuhp_state target) +{ + enum cpuhp_state prev_state = st->state; + int ret = 0; + + while (st->state < target) { + struct cpuhp_step *step; + + st->state++; + step = steps + st->state; + ret = cpuhp_invoke_callback(cpu, st->state, step->startup); + if (ret) { + st->target = prev_state; + undo_cpu_up(cpu, st, steps); + break; + } + } + 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_TEARDOWN_CPU); + + 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 { + /* Cannot happen .... */ + BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE); + + /* 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 void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st) +{ + 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); +} + +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); + __cpuhp_kick_ap_work(st); + 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); - void unregister_cpu_notifier(struct notifier_block *nb) { cpu_maps_update_begin(); @@ -464,6 +688,7 @@ static int take_cpu_down(void *_param) static int takedown_cpu(unsigned int cpu) { + struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); int err; /* @@ -481,6 +706,8 @@ static int takedown_cpu(unsigned int cpu) else synchronize_rcu(); + /* Park the smpboot threads */ + kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread); smpboot_park_threads(cpu); /* @@ -508,10 +735,8 @@ static int takedown_cpu(unsigned int cpu) * * Wait for the stop thread to go away. */ - while (!per_cpu(cpu_dead_idle, cpu)) - cpu_relax(); - smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */ - per_cpu(cpu_dead_idle, cpu) = false; + wait_for_completion(&st->done); + BUG_ON(st->state != CPUHP_AP_IDLE_DEAD); /* Interrupts are moved away from the dying cpu, reenable alloc/free */ irq_unlock_sparse(); @@ -531,6 +756,28 @@ static int notify_dead(unsigned int cpu) return 0; } +static void cpuhp_complete_idle_dead(void *arg) +{ + struct cpuhp_cpu_state *st = arg; + + complete(&st->done); +} + +void cpuhp_report_idle_dead(void) +{ + struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); + + BUG_ON(st->state != CPUHP_AP_OFFLINE); + rcu_report_dead(smp_processor_id()); + st->state = CPUHP_AP_IDLE_DEAD; + /* + * We cannot call complete after rcu_report_dead() so we delegate it + * to an online cpu. + */ + smp_call_function_single(cpumask_first(cpu_online_mask), + cpuhp_complete_idle_dead, st, 0); +} + #else #define notify_down_prepare NULL #define takedown_cpu NULL @@ -539,15 +786,6 @@ static int notify_dead(unsigned int cpu) #endif #ifdef CONFIG_HOTPLUG_CPU -static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st) -{ - for (st->state++; st->state < st->target; st->state++) { - struct cpuhp_step *step = cpuhp_bp_states + st->state; - - if (!step->skip_onerr) - cpuhp_invoke_callback(cpu, st->state, step->startup); - } -} /* Requires cpu_add_remove_lock to be held */ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen, @@ -569,18 +807,34 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen, prev_state = st->state; st->target = target; - for (; st->state > st->target; st->state--) { - struct cpuhp_step *step = cpuhp_bp_states + st->state; + /* + * If the current CPU state is in the range of the AP hotplug thread, + * then we need to kick the thread. + */ + if (st->state > CPUHP_TEARDOWN_CPU) { + ret = cpuhp_kick_ap_work(cpu); + /* + * The AP side has done the error rollback already. Just + * return the error code.. + */ + if (ret) + goto out; - ret = cpuhp_invoke_callback(cpu, st->state, step->teardown); - if (ret) { - st->target = prev_state; - undo_cpu_down(cpu, st); - break; - } + /* + * We might have stopped still in the range of the AP hotplug + * thread. Nothing to do anymore. + */ + if (st->state > CPUHP_TEARDOWN_CPU) + goto out; } - hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE; + /* + * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need + * to do the further cleanups. + */ + ret = cpuhp_down_callbacks(cpu, st, cpuhp_bp_states, target); + hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE; +out: cpu_hotplug_done(); /* This post dead nonsense must die */ if (!ret && hasdied) @@ -612,38 +866,6 @@ int cpu_down(unsigned int cpu) EXPORT_SYMBOL(cpu_down); #endif /*CONFIG_HOTPLUG_CPU*/ -/* - * Unpark per-CPU smpboot kthreads at CPU-online time. - */ -static int smpboot_thread_call(struct notifier_block *nfb, - unsigned long action, void *hcpu) -{ - int cpu = (long)hcpu; - - switch (action & ~CPU_TASKS_FROZEN) { - - case CPU_DOWN_FAILED: - case CPU_ONLINE: - smpboot_unpark_threads(cpu); - break; - - default: - break; - } - - return NOTIFY_OK; -} - -static struct notifier_block smpboot_thread_notifier = { - .notifier_call = smpboot_thread_call, - .priority = CPU_PRI_SMPBOOT, -}; - -void smpboot_thread_init(void) -{ - register_cpu_notifier(&smpboot_thread_notifier); -} - /** * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers * @cpu: cpu that just started @@ -666,14 +888,34 @@ void notify_cpu_starting(unsigned int cpu) } } -static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st) +/* + * Called from the idle task. We need to set active here, so we can kick off + * the stopper thread and unpark the smpboot threads. If the target state is + * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the + * cpu further. + */ +void cpuhp_online_idle(enum cpuhp_state state) { - for (st->state--; st->state > st->target; st->state--) { - struct cpuhp_step *step = cpuhp_bp_states + st->state; + struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state); + unsigned int cpu = smp_processor_id(); - if (!step->skip_onerr) - cpuhp_invoke_callback(cpu, st->state, step->teardown); - } + /* Happens for the boot cpu */ + if (state != CPUHP_AP_ONLINE_IDLE) + return; + + st->state = CPUHP_AP_ONLINE_IDLE; + + /* The cpu is marked online, set it active now */ + set_cpu_active(cpu, true); + /* Unpark the stopper thread and the hotplug thread of this cpu */ + stop_machine_unpark(cpu); + kthread_unpark(st->thread); + + /* Should we go further up ? */ + if (st->target > CPUHP_AP_ONLINE_IDLE) + __cpuhp_kick_ap_work(st); + else + complete(&st->done); } /* Requires cpu_add_remove_lock to be held */ @@ -681,7 +923,7 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target) { struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); struct task_struct *idle; - int prev_state, ret = 0; + int ret = 0; cpu_hotplug_begin(); @@ -708,20 +950,28 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target) cpuhp_tasks_frozen = tasks_frozen; - prev_state = st->state; st->target = target; - while (st->state < st->target) { - struct cpuhp_step *step; - - st->state++; - step = cpuhp_bp_states + st->state; - ret = cpuhp_invoke_callback(cpu, st->state, step->startup); - if (ret) { - st->target = prev_state; - undo_cpu_up(cpu, st); - break; - } + /* + * If the current CPU state is in the range of the AP hotplug thread, + * then we need to kick the thread once more. + */ + if (st->state > CPUHP_BRINGUP_CPU) { + ret = cpuhp_kick_ap_work(cpu); + /* + * The AP side has done the error rollback already. Just + * return the error code.. + */ + if (ret) + goto out; } + + /* + * Try to reach the target state. We max out on the BP at + * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is + * responsible for bringing it up to the target state. + */ + target = min((int)target, CPUHP_BRINGUP_CPU); + ret = cpuhp_up_callbacks(cpu, st, cpuhp_bp_states, target); out: cpu_hotplug_done(); return ret; @@ -922,6 +1172,10 @@ static struct cpuhp_step cpuhp_bp_states[] = { .teardown = NULL, .cant_stop = true, }, + /* + * Preparatory and dead notifiers. Will be replaced once the notifiers + * are converted to states. + */ [CPUHP_NOTIFY_PREPARE] = { .name = "notify:prepare", .startup = notify_prepare, @@ -929,35 +1183,46 @@ static struct cpuhp_step cpuhp_bp_states[] = { .skip_onerr = true, .cant_stop = true, }, + /* Kicks the plugged cpu into life */ [CPUHP_BRINGUP_CPU] = { .name = "cpu:bringup", .startup = bringup_cpu, .teardown = NULL, .cant_stop = true, }, + /* + * Handled on controll processor until the plugged processor manages + * this itself. + */ [CPUHP_TEARDOWN_CPU] = { .name = "cpu:teardown", .startup = NULL, .teardown = takedown_cpu, .cant_stop = true, }, - [CPUHP_NOTIFY_ONLINE] = { - .name = "notify:online", - .startup = notify_online, - .teardown = notify_down_prepare, - .cant_stop = true, - }, #endif - [CPUHP_ONLINE] = { - .name = "online", - .startup = NULL, - .teardown = NULL, - }, }; /* Application processor state steps */ static struct cpuhp_step cpuhp_ap_states[] = { #ifdef CONFIG_SMP + /* Final state before CPU kills itself */ + [CPUHP_AP_IDLE_DEAD] = { + .name = "idle:dead", + }, + /* + * Last state before CPU enters the idle loop to die. Transient state + * for synchronization. + */ + [CPUHP_AP_OFFLINE] = { + .name = "ap:offline", + .cant_stop = true, + }, + /* + * Low level startup/teardown notifiers. Run with interrupts + * disabled. Will be removed once the notifiers are converted to + * states. + */ [CPUHP_AP_NOTIFY_STARTING] = { .name = "notify:starting", .startup = notify_starting, @@ -965,7 +1230,32 @@ static struct cpuhp_step cpuhp_ap_states[] = { .skip_onerr = true, .cant_stop = true, }, + /* Entry state on starting. Interrupts enabled from here on. Transient + * state for synchronsization */ + [CPUHP_AP_ONLINE] = { + .name = "ap:online", + }, + /* Handle smpboot threads park/unpark */ + [CPUHP_AP_SMPBOOT_THREADS] = { + .name = "smpboot:threads", + .startup = smpboot_unpark_threads, + .teardown = NULL, + }, + /* + * Online/down_prepare notifiers. Will be removed once the notifiers + * are converted to states. + */ + [CPUHP_AP_NOTIFY_ONLINE] = { + .name = "notify:online", + .startup = notify_online, + .teardown = notify_down_prepare, + }, #endif + /* + * The dynamically registered state space is here + */ + + /* CPU is fully up and running. */ [CPUHP_ONLINE] = { .name = "online", .startup = NULL, @@ -983,7 +1273,11 @@ 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); + /* + * The extra check for CPUHP_TEARDOWN_CPU is only for documentation + * purposes as that state is handled explicitely in cpu_down. + */ + return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU; } static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state) @@ -1015,14 +1309,6 @@ static void *cpuhp_get_teardown_cb(enum cpuhp_state state) return cpuhp_get_step(state)->teardown; } -/* Helper function to run callback on the target cpu */ -static void cpuhp_on_cpu_cb(void *__cb) -{ - int (*cb)(unsigned int cpu) = __cb; - - BUG_ON(cb(smp_processor_id())); -} - /* * Call the startup/teardown function for a step either on the AP or * on the current CPU. @@ -1034,26 +1320,18 @@ static int cpuhp_issue_call(int cpu, enum cpuhp_state state, if (!cb) return 0; - - /* - * This invokes the callback directly for now. In a later step we - * convert that to use cpuhp_invoke_callback(). - */ - if (cpuhp_is_ap_state(state)) { - /* - * Note, that a function called on the AP is not - * allowed to fail. - */ - if (cpu_online(cpu)) - smp_call_function_single(cpu, cpuhp_on_cpu_cb, cb, 1); - return 0; - } - /* * The non AP bound callbacks can fail on bringup. On teardown * e.g. module removal we crash for now. */ - ret = cb(cpu); +#ifdef CONFIG_SMP + if (cpuhp_is_ap_state(state)) + ret = cpuhp_invoke_ap_callback(cpu, state, cb); + else + ret = cpuhp_invoke_callback(cpu, state, cb); +#else + ret = cpuhp_invoke_callback(cpu, state, cb); +#endif BUG_ON(ret && !bringup); return ret; } @@ -1095,11 +1373,11 @@ static int cpuhp_reserve_state(enum cpuhp_state state) enum cpuhp_state i; mutex_lock(&cpuhp_state_mutex); - for (i = CPUHP_ONLINE_DYN; i <= CPUHP_ONLINE_DYN_END; i++) { - if (cpuhp_bp_states[i].name) + for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) { + if (cpuhp_ap_states[i].name) continue; - cpuhp_bp_states[i].name = "Reserved"; + cpuhp_ap_states[i].name = "Reserved"; mutex_unlock(&cpuhp_state_mutex); return i; } @@ -1132,7 +1410,7 @@ int __cpuhp_setup_state(enum cpuhp_state state, get_online_cpus(); /* currently assignments for the ONLINE state are possible */ - if (state == CPUHP_ONLINE_DYN) { + if (state == CPUHP_AP_ONLINE_DYN) { dyn_state = 1; ret = cpuhp_reserve_state(state); if (ret < 0)