Make stop_machine() safe to call early in boot, before SMP has been set up, by simply calling the callback function directly if there's only one CPU online. [ Fixes from AKPM: - add comment - local_irq_flags, not save_flags - also call hard_irq_disable() for systems which need it Tejun suggested using an explicit flag rather than just looking at the online cpu count. ]
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| @@ -41,6 +41,7 @@ struct cpu_stopper { · 40 unmodified lines | |||
| 41 | }; | 41 | }; |
| 42 | 42 | ||
| 43 | static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper); | 43 | static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper); |
| 44 | static bool stop_machine_initialized = false; | ||
| 44 | 45 | ||
| 45 | static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo) | 46 | static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo) |
| 46 | { | 47 | { |
| @@ -386,6 +387,8 @@ static int __init cpu_stop_init(void) · 339 unmodified lines | |||
| 386 | cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu); | 387 | cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu); |
| 387 | register_cpu_notifier(&cpu_stop_cpu_notifier); | 388 | register_cpu_notifier(&cpu_stop_cpu_notifier); |
| 388 | 389 | ||
| 390 | stop_machine_initialized = true; | ||
| 391 | |||
| 389 | return 0; | 392 | return 0; |
| 390 | } | 393 | } |
| 391 | early_initcall(cpu_stop_init); | 394 | early_initcall(cpu_stop_init); |
| @@ -485,6 +488,25 @@ int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) · 93 unmodified lines | |||
| 485 | .num_threads = num_online_cpus(), | 488 | .num_threads = num_online_cpus(), |
| 486 | .active_cpus = cpus }; | 489 | .active_cpus = cpus }; |
| 487 | 490 | ||
| 491 | if (!stop_machine_initialized) { | ||
| 492 | /* | ||
| 493 | * Handle the case where stop_machine() is called | ||
| 494 | * early in boot before stop_machine() has been | ||
| 495 | * initialized. | ||
| 496 | */ | ||
| 497 | unsigned long flags; | ||
| 498 | int ret; | ||
| 499 | |||
| 500 | WARN_ON_ONCE(smdata.num_threads != 1); | ||
| 501 | |||
| 502 | local_irq_save(flags); | ||
| 503 | hard_irq_disable(); | ||
| 504 | ret = (*fn)(data); | ||
| 505 | local_irq_restore(flags); | ||
| 506 | |||
| 507 | return ret; | ||
| 508 | } | ||
| 509 | |||
| 488 | /* Set the initial state and stop all online cpus. */ | 510 | /* Set the initial state and stop all online cpus. */ |
| 489 | set_state(&smdata, STOPMACHINE_PREPARE); | 511 | set_state(&smdata, STOPMACHINE_PREPARE); |
| 490 | return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata); | 512 | return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata); |