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-rw-r--r--include/linux/sched.h3
-rw-r--r--kernel/cpu.c16
-rw-r--r--kernel/sched.c206
3 files changed, 67 insertions, 158 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3cd70cf91fde..29d953abb5ad 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1871,14 +1871,11 @@ extern void sched_clock_idle_sleep_event(void);
extern void sched_clock_idle_wakeup_event(u64 delta_ns);
#ifdef CONFIG_HOTPLUG_CPU
-extern void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p);
extern void idle_task_exit(void);
#else
static inline void idle_task_exit(void) {}
#endif
-extern void sched_idle_next(void);
-
#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
extern void wake_up_idle_cpu(int cpu);
#else
diff --git a/kernel/cpu.c b/kernel/cpu.c
index f6e726f18491..8615aa65d927 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -189,7 +189,6 @@ static inline void check_for_tasks(int cpu)
}
struct take_cpu_down_param {
- struct task_struct *caller;
unsigned long mod;
void *hcpu;
};
@@ -208,11 +207,6 @@ static int __ref take_cpu_down(void *_param)
cpu_notify(CPU_DYING | param->mod, param->hcpu);
- if (task_cpu(param->caller) == cpu)
- move_task_off_dead_cpu(cpu, param->caller);
- /* Force idle task to run as soon as we yield: it should
- immediately notice cpu is offline and die quickly. */
- sched_idle_next();
return 0;
}
@@ -223,7 +217,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
void *hcpu = (void *)(long)cpu;
unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
struct take_cpu_down_param tcd_param = {
- .caller = current,
.mod = mod,
.hcpu = hcpu,
};
@@ -253,9 +246,12 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
}
BUG_ON(cpu_online(cpu));
- /* Wait for it to sleep (leaving idle task). */
- while (!idle_cpu(cpu))
- yield();
+ /*
+ * The migration_call() CPU_DYING callback will have removed all
+ * runnable tasks from the cpu, there's only the idle task left now
+ * that the migration thread is done doing the stop_machine thing.
+ */
+ BUG_ON(!idle_cpu(cpu));
/* This actually kills the CPU. */
__cpu_die(cpu);
diff --git a/kernel/sched.c b/kernel/sched.c
index 41f18695b730..b0d5f1b24a39 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2366,18 +2366,15 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
return dest_cpu;
/* No more Mr. Nice Guy. */
- if (unlikely(dest_cpu >= nr_cpu_ids)) {
- dest_cpu = cpuset_cpus_allowed_fallback(p);
- /*
- * Don't tell them about moving exiting tasks or
- * kernel threads (both mm NULL), since they never
- * leave kernel.
- */
- if (p->mm && printk_ratelimit()) {
- printk(KERN_INFO "process %d (%s) no "
- "longer affine to cpu%d\n",
- task_pid_nr(p), p->comm, cpu);
- }
+ dest_cpu = cpuset_cpus_allowed_fallback(p);
+ /*
+ * Don't tell them about moving exiting tasks or
+ * kernel threads (both mm NULL), since they never
+ * leave kernel.
+ */
+ if (p->mm && printk_ratelimit()) {
+ printk(KERN_INFO "process %d (%s) no longer affine to cpu%d\n",
+ task_pid_nr(p), p->comm, cpu);
}
return dest_cpu;
@@ -5712,29 +5709,20 @@ static int migration_cpu_stop(void *data)
}
#ifdef CONFIG_HOTPLUG_CPU
+
/*
- * Figure out where task on dead CPU should go, use force if necessary.
+ * Ensures that the idle task is using init_mm right before its cpu goes
+ * offline.
*/
-void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
+void idle_task_exit(void)
{
- struct rq *rq = cpu_rq(dead_cpu);
- int needs_cpu, uninitialized_var(dest_cpu);
- unsigned long flags;
+ struct mm_struct *mm = current->active_mm;
- local_irq_save(flags);
+ BUG_ON(cpu_online(smp_processor_id()));
- raw_spin_lock(&rq->lock);
- needs_cpu = (task_cpu(p) == dead_cpu) && (p->state != TASK_WAKING);
- if (needs_cpu)
- dest_cpu = select_fallback_rq(dead_cpu, p);
- raw_spin_unlock(&rq->lock);
- /*
- * It can only fail if we race with set_cpus_allowed(),
- * in the racer should migrate the task anyway.
- */
- if (needs_cpu)
- __migrate_task(p, dead_cpu, dest_cpu);
- local_irq_restore(flags);
+ if (mm != &init_mm)
+ switch_mm(mm, &init_mm, current);
+ mmdrop(mm);
}
/*
@@ -5747,128 +5735,69 @@ void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
static void migrate_nr_uninterruptible(struct rq *rq_src)
{
struct rq *rq_dest = cpu_rq(cpumask_any(cpu_active_mask));
- unsigned long flags;
- local_irq_save(flags);
- double_rq_lock(rq_src, rq_dest);
rq_dest->nr_uninterruptible += rq_src->nr_uninterruptible;
rq_src->nr_uninterruptible = 0;
- double_rq_unlock(rq_src, rq_dest);
- local_irq_restore(flags);
-}
-
-/* Run through task list and migrate tasks from the dead cpu. */
-static void migrate_live_tasks(int src_cpu)
-{
- struct task_struct *p, *t;
-
- read_lock(&tasklist_lock);
-
- do_each_thread(t, p) {
- if (p == current)
- continue;
-
- if (task_cpu(p) == src_cpu)
- move_task_off_dead_cpu(src_cpu, p);
- } while_each_thread(t, p);
-
- read_unlock(&tasklist_lock);
}
/*
- * Schedules idle task to be the next runnable task on current CPU.
- * It does so by boosting its priority to highest possible.
- * Used by CPU offline code.
+ * remove the tasks which were accounted by rq from calc_load_tasks.
*/
-void sched_idle_next(void)
+static void calc_global_load_remove(struct rq *rq)
{
- int this_cpu = smp_processor_id();
- struct rq *rq = cpu_rq(this_cpu);
- struct task_struct *p = rq->idle;
- unsigned long flags;
-
- /* cpu has to be offline */
- BUG_ON(cpu_online(this_cpu));
-
- /*
- * Strictly not necessary since rest of the CPUs are stopped by now
- * and interrupts disabled on the current cpu.
- */
- raw_spin_lock_irqsave(&rq->lock, flags);
-
- __setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);
-
- activate_task(rq, p, 0);
-
- raw_spin_unlock_irqrestore(&rq->lock, flags);
+ atomic_long_sub(rq->calc_load_active, &calc_load_tasks);
+ rq->calc_load_active = 0;
}
/*
- * Ensures that the idle task is using init_mm right before its cpu goes
- * offline.
+ * Migrate all tasks from the rq, sleeping tasks will be migrated by
+ * try_to_wake_up()->select_task_rq().
+ *
+ * Called with rq->lock held even though we'er in stop_machine() and
+ * there's no concurrency possible, we hold the required locks anyway
+ * because of lock validation efforts.
*/
-void idle_task_exit(void)
-{
- struct mm_struct *mm = current->active_mm;
-
- BUG_ON(cpu_online(smp_processor_id()));
-
- if (mm != &init_mm)
- switch_mm(mm, &init_mm, current);
- mmdrop(mm);
-}
-
-/* called under rq->lock with disabled interrupts */
-static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)
+static void migrate_tasks(unsigned int dead_cpu)
{
struct rq *rq = cpu_rq(dead_cpu);
-
- /* Must be exiting, otherwise would be on tasklist. */
- BUG_ON(!p->exit_state);
-
- /* Cannot have done final schedule yet: would have vanished. */
- BUG_ON(p->state == TASK_DEAD);
-
- get_task_struct(p);
+ struct task_struct *next, *stop = rq->stop;
+ int dest_cpu;
/*
- * Drop lock around migration; if someone else moves it,
- * that's OK. No task can be added to this CPU, so iteration is
- * fine.
+ * Fudge the rq selection such that the below task selection loop
+ * doesn't get stuck on the currently eligible stop task.
+ *
+ * We're currently inside stop_machine() and the rq is either stuck
+ * in the stop_machine_cpu_stop() loop, or we're executing this code,
+ * either way we should never end up calling schedule() until we're
+ * done here.
*/
- raw_spin_unlock_irq(&rq->lock);
- move_task_off_dead_cpu(dead_cpu, p);
- raw_spin_lock_irq(&rq->lock);
-
- put_task_struct(p);
-}
-
-/* release_task() removes task from tasklist, so we won't find dead tasks. */
-static void migrate_dead_tasks(unsigned int dead_cpu)
-{
- struct rq *rq = cpu_rq(dead_cpu);
- struct task_struct *next;
+ rq->stop = NULL;
for ( ; ; ) {
- if (!rq->nr_running)
+ /*
+ * There's this thread running, bail when that's the only
+ * remaining thread.
+ */
+ if (rq->nr_running == 1)
break;
+
next = pick_next_task(rq);
- if (!next)
- break;
+ BUG_ON(!next);
next->sched_class->put_prev_task(rq, next);
- migrate_dead(dead_cpu, next);
+ /* Find suitable destination for @next, with force if needed. */
+ dest_cpu = select_fallback_rq(dead_cpu, next);
+ raw_spin_unlock(&rq->lock);
+
+ __migrate_task(next, dead_cpu, dest_cpu);
+
+ raw_spin_lock(&rq->lock);
}
-}
-/*
- * remove the tasks which were accounted by rq from calc_load_tasks.
- */
-static void calc_global_load_remove(struct rq *rq)
-{
- atomic_long_sub(rq->calc_load_active, &calc_load_tasks);
- rq->calc_load_active = 0;
+ rq->stop = stop;
}
+
#endif /* CONFIG_HOTPLUG_CPU */
#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL)
@@ -6078,15 +6007,13 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
unsigned long flags;
struct rq *rq = cpu_rq(cpu);
- switch (action) {
+ switch (action & ~CPU_TASKS_FROZEN) {
case CPU_UP_PREPARE:
- case CPU_UP_PREPARE_FROZEN:
rq->calc_load_update = calc_load_update;
break;
case CPU_ONLINE:
- case CPU_ONLINE_FROZEN:
/* Update our root-domain */
raw_spin_lock_irqsave(&rq->lock, flags);
if (rq->rd) {
@@ -6098,30 +6025,19 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
break;
#ifdef CONFIG_HOTPLUG_CPU
- case CPU_DEAD:
- case CPU_DEAD_FROZEN:
- migrate_live_tasks(cpu);
- /* Idle task back to normal (off runqueue, low prio) */
- raw_spin_lock_irq(&rq->lock);
- deactivate_task(rq, rq->idle, 0);
- __setscheduler(rq, rq->idle, SCHED_NORMAL, 0);
- rq->idle->sched_class = &idle_sched_class;
- migrate_dead_tasks(cpu);
- raw_spin_unlock_irq(&rq->lock);
- migrate_nr_uninterruptible(rq);
- BUG_ON(rq->nr_running != 0);
- calc_global_load_remove(rq);
- break;
-
case CPU_DYING:
- case CPU_DYING_FROZEN:
/* Update our root-domain */
raw_spin_lock_irqsave(&rq->lock, flags);
if (rq->rd) {
BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
set_rq_offline(rq);
}
+ migrate_tasks(cpu);
+ BUG_ON(rq->nr_running != 1); /* the migration thread */
raw_spin_unlock_irqrestore(&rq->lock, flags);
+
+ migrate_nr_uninterruptible(rq);
+ calc_global_load_remove(rq);
break;
#endif
}
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