diff options
author | Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> | 2011-10-31 20:11:15 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-10-31 20:30:53 -0400 |
commit | f445027e4e692bd885118460b292d08027fd5501 (patch) | |
tree | e7791443970d45ffede0f23018676d508a1f1149 /kernel/stop_machine.c | |
parent | aaaa287b89a09f22573dc57fcbb6a7dc7d25c8ed (diff) |
stop_machine: make stop_machine safe and efficient to call early
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. ]
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Tejun Heo <htejun@gmail.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/stop_machine.c')
-rw-r--r-- | kernel/stop_machine.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index ba5070ce5765..5b0951aa0496 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c | |||
@@ -41,6 +41,7 @@ struct cpu_stopper { | |||
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) | |||
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) | |||
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); |