From c00166d87e730088d919814020e96ffed129d0d1 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 9 Oct 2015 18:00:49 +0200 Subject: [PATCH] stop_machine: Kill smp_hotplug_thread->pre_unpark, introduce stop_machine_unpark() 1. Change smpboot_unpark_thread() to check ->selfparking, just like smpboot_park_thread() does. 2. Introduce stop_machine_unpark() which sets ->enabled and calls kthread_unpark(). 3. Change smpboot_thread_call() and cpu_stop_init() to call stop_machine_unpark() by hand. This way: - IMO the ->selfparking logic becomes more consistent. - We can kill the smp_hotplug_thread->pre_unpark() method. - We can easily unpark the stopper thread earlier. Say, we can move stop_machine_unpark() from smpboot_thread_call() to sched_cpu_active() as Peter suggests. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Tejun Heo Cc: Thomas Gleixner Cc: heiko.carstens@de.ibm.com Link: http://lkml.kernel.org/r/20151009160049.GA10166@redhat.com Signed-off-by: Ingo Molnar --- include/linux/smpboot.h | 4 ---- include/linux/stop_machine.h | 1 + kernel/cpu.c | 1 + kernel/smpboot.c | 5 ++--- kernel/stop_machine.c | 10 +++++++++- 5 files changed, 13 insertions(+), 8 deletions(-) diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h index e6109a6..12910cf 100644 --- a/include/linux/smpboot.h +++ b/include/linux/smpboot.h @@ -24,9 +24,6 @@ struct smpboot_thread_data; * parked (cpu offline) * @unpark: Optional unpark function, called when the thread is * unparked (cpu online) - * @pre_unpark: Optional unpark function, called before the thread is - * unparked (cpu online). This is not guaranteed to be - * called on the target cpu of the thread. Careful! * @cpumask: Internal state. To update which threads are unparked, * call smpboot_update_cpumask_percpu_thread(). * @selfparking: Thread is not parked by the park function. @@ -42,7 +39,6 @@ struct smp_hotplug_thread { void (*cleanup)(unsigned int cpu, bool online); void (*park)(unsigned int cpu); void (*unpark)(unsigned int cpu); - void (*pre_unpark)(unsigned int cpu); cpumask_var_t cpumask; bool selfparking; const char *thread_comm; diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h index 7b76362..0adedca 100644 --- a/include/linux/stop_machine.h +++ b/include/linux/stop_machine.h @@ -34,6 +34,7 @@ void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg); int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg); void stop_machine_park(int cpu); +void stop_machine_unpark(int cpu); #else /* CONFIG_SMP */ diff --git a/kernel/cpu.c b/kernel/cpu.c index c85df27..6467521 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -475,6 +475,7 @@ static int smpboot_thread_call(struct notifier_block *nfb, case CPU_DOWN_FAILED: case CPU_ONLINE: + stop_machine_unpark(cpu); smpboot_unpark_threads(cpu); break; diff --git a/kernel/smpboot.c b/kernel/smpboot.c index a818cbc..d264f59 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -222,9 +222,8 @@ static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cp { struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu); - if (ht->pre_unpark) - ht->pre_unpark(cpu); - kthread_unpark(tsk); + if (!ht->selfparking) + kthread_unpark(tsk); } void smpboot_unpark_threads(unsigned int cpu) diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 91fbb10..59096a5 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -513,6 +513,14 @@ static void cpu_stop_unpark(unsigned int cpu) spin_unlock_irq(&stopper->lock); } +void stop_machine_unpark(int cpu) +{ + struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); + + cpu_stop_unpark(cpu); + kthread_unpark(stopper->thread); +} + static struct smp_hotplug_thread cpu_stop_threads = { .store = &cpu_stopper.thread, .thread_should_run = cpu_stop_should_run, @@ -521,7 +529,6 @@ static struct smp_hotplug_thread cpu_stop_threads = { .create = cpu_stop_create, .setup = cpu_stop_unpark, .park = cpu_stop_park, - .pre_unpark = cpu_stop_unpark, .selfparking = true, }; @@ -537,6 +544,7 @@ static int __init cpu_stop_init(void) } BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads)); + stop_machine_unpark(raw_smp_processor_id()); stop_machine_initialized = true; return 0; } -- 2.7.4