Messages in this thread Patch in this message | | | Date | Thu, 14 Jun 2012 13:01:29 -0700 | From | Silas Boyd-Wickizer <> | Subject | Re: [RFC patch 1/5] kthread: Implement park/unpark facility |
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Hello,
I've taken a stab at converting stop_machine to use kthread_park and kthread_unpark. I don't think stop_machine can use smpboot_park_threads (in their current implementation) because, among other reasons, _cpu_down calls __stop_machine after parking the stopper threads via smpboot_park_threads.
Silas
Signed-off-by: Silas Boyd-Wickizer <sbw@mit.edu> --- kernel/stop_machine.c | 41 ++++++++++++++++++----------------------- 1 file changed, 18 insertions(+), 23 deletions(-)
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 2f194e9..631f133 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -244,7 +244,7 @@ int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) return ret; } -static int cpu_stopper_thread(void *data) +static __noreturn int cpu_stopper_thread(void *data) { struct cpu_stopper *stopper = data; struct cpu_stop_work *work; @@ -253,10 +253,8 @@ static int cpu_stopper_thread(void *data) repeat: set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */ - if (kthread_should_stop()) { - __set_current_state(TASK_RUNNING); - return 0; - } + if (kthread_should_park()) + kthread_parkme(); work = NULL; spin_lock_irq(&stopper->lock); @@ -308,23 +306,23 @@ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, switch (action & ~CPU_TASKS_FROZEN) { case CPU_UP_PREPARE: - BUG_ON(stopper->thread || stopper->enabled || - !list_empty(&stopper->works)); - p = kthread_create_on_node(cpu_stopper_thread, - stopper, - cpu_to_node(cpu), - "migration/%d", cpu); - if (IS_ERR(p)) - return notifier_from_errno(PTR_ERR(p)); - get_task_struct(p); - kthread_bind(p, cpu); - sched_set_stop_task(cpu, p); - stopper->thread = p; + if (!stopper->thread) { + BUG_ON(stopper->enabled || + !list_empty(&stopper->works)); + p = kthread_create_on_cpu(cpu_stopper_thread, + stopper, + cpu, + "migration/%d"); + if (IS_ERR(p)) + return notifier_from_errno(PTR_ERR(p)); + get_task_struct(p); + stopper->thread = p; + } + sched_set_stop_task(cpu, stopper->thread); break; case CPU_ONLINE: - /* strictly unnecessary, as first user will wake it */ - wake_up_process(stopper->thread); + kthread_unpark(stopper->thread); /* mark enabled */ spin_lock_irq(&stopper->lock); stopper->enabled = true; @@ -339,16 +337,13 @@ static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, sched_set_stop_task(cpu, NULL); /* kill the stopper */ - kthread_stop(stopper->thread); + kthread_park(stopper->thread); /* drain remaining works */ spin_lock_irq(&stopper->lock); list_for_each_entry(work, &stopper->works, list) cpu_stop_signal_done(work->done, false); stopper->enabled = false; spin_unlock_irq(&stopper->lock); - /* release the stopper */ - put_task_struct(stopper->thread); - stopper->thread = NULL; break; } #endif
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