diff options
author | Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> | 2011-11-01 04:11:15 +0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-11-01 04:30:53 +0400 |
commit | f445027e4e692bd885118460b292d08027fd5501 (patch) | |
tree | e7791443970d45ffede0f23018676d508a1f1149 | |
parent | aaaa287b89a09f22573dc57fcbb6a7dc7d25c8ed (diff) | |
download | linux-f445027e4e692bd885118460b292d08027fd5501.tar.xz |
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>
-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 { }; static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper); +static bool stop_machine_initialized = false; static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo) { @@ -386,6 +387,8 @@ static int __init cpu_stop_init(void) cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu); register_cpu_notifier(&cpu_stop_cpu_notifier); + stop_machine_initialized = true; + return 0; } early_initcall(cpu_stop_init); @@ -485,6 +488,25 @@ int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) .num_threads = num_online_cpus(), .active_cpus = cpus }; + if (!stop_machine_initialized) { + /* + * Handle the case where stop_machine() is called + * early in boot before stop_machine() has been + * initialized. + */ + unsigned long flags; + int ret; + + WARN_ON_ONCE(smdata.num_threads != 1); + + local_irq_save(flags); + hard_irq_disable(); + ret = (*fn)(data); + local_irq_restore(flags); + + return ret; + } + /* Set the initial state and stop all online cpus. */ set_state(&smdata, STOPMACHINE_PREPARE); return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata); |