#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/percpu.h>
-#include <linux/kthread.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
+#include <linux/stop_machine.h>
#include <linux/sysctl.h>
#include <linux/syscalls.h>
#include <linux/times.h>
/* Change a task's cfs_rq and parent entity if it moves across CPUs/groups */
static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
{
+ /*
+ * Strictly speaking this rcu_read_lock() is not needed since the
+ * task_group is tied to the cgroup, which in turn can never go away
+ * as long as there are tasks attached to it.
+ *
+ * However since task_group() uses task_subsys_state() which is an
+ * rcu_dereference() user, this quiets CONFIG_PROVE_RCU.
+ */
+ rcu_read_lock();
#ifdef CONFIG_FAIR_GROUP_SCHED
p->se.cfs_rq = task_group(p)->cfs_rq[cpu];
p->se.parent = task_group(p)->se[cpu];
p->rt.rt_rq = task_group(p)->rt_rq[cpu];
p->rt.parent = task_group(p)->rt_se[cpu];
#endif
+ rcu_read_unlock();
}
#else
int post_schedule;
int active_balance;
int push_cpu;
+ struct cpu_stop_work active_balance_work;
/* cpu of this runqueue: */
int cpu;
int online;
unsigned long avg_load_per_task;
- struct task_struct *migration_thread;
- struct list_head migration_queue;
-
u64 rt_avg;
u64 age_stamp;
u64 idle_stamp;
}
#endif
-static void calc_load_account_active(struct rq *this_rq);
+static void calc_load_account_idle(struct rq *this_rq);
static void update_sysctl(void);
static int get_update_sysctl_factor(void);
__set_task_cpu(p, new_cpu);
}
-struct migration_req {
- struct list_head list;
-
+struct migration_arg {
struct task_struct *task;
int dest_cpu;
-
- struct completion done;
};
+static int migration_cpu_stop(void *data);
+
/*
* The task's runqueue lock must be held.
* Returns true if you have to wait for migration thread.
*/
-static int
-migrate_task(struct task_struct *p, int dest_cpu, struct migration_req *req)
+static bool migrate_task(struct task_struct *p, int dest_cpu)
{
struct rq *rq = task_rq(p);
* If the task is not on a runqueue (and not running), then
* the next wake-up will properly place the task.
*/
- if (!p->se.on_rq && !task_running(rq, p))
- return 0;
-
- init_completion(&req->done);
- req->task = p;
- req->dest_cpu = dest_cpu;
- list_add(&req->list, &rq->migration_queue);
-
- return 1;
-}
-
-/*
- * wait_task_context_switch - wait for a thread to complete at least one
- * context switch.
- *
- * @p must not be current.
- */
-void wait_task_context_switch(struct task_struct *p)
-{
- unsigned long nvcsw, nivcsw, flags;
- int running;
- struct rq *rq;
-
- nvcsw = p->nvcsw;
- nivcsw = p->nivcsw;
- for (;;) {
- /*
- * The runqueue is assigned before the actual context
- * switch. We need to take the runqueue lock.
- *
- * We could check initially without the lock but it is
- * very likely that we need to take the lock in every
- * iteration.
- */
- rq = task_rq_lock(p, &flags);
- running = task_running(rq, p);
- task_rq_unlock(rq, &flags);
-
- if (likely(!running))
- break;
- /*
- * The switch count is incremented before the actual
- * context switch. We thus wait for two switches to be
- * sure at least one completed.
- */
- if ((p->nvcsw - nvcsw) > 1)
- break;
- if ((p->nivcsw - nivcsw) > 1)
- break;
-
- cpu_relax();
- }
+ return p->se.on_rq || task_running(rq, p);
}
/*
* just go back and repeat.
*/
rq = task_rq_lock(p, &flags);
- trace_sched_wait_task(rq, p);
+ trace_sched_wait_task(p);
running = task_running(rq, p);
on_rq = p->se.on_rq;
ncsw = 0;
success = 1;
out_running:
- trace_sched_wakeup(rq, p, success);
+ trace_sched_wakeup(p, success);
check_preempt_curr(rq, p, wake_flags);
p->state = TASK_RUNNING;
rq = task_rq_lock(p, &flags);
activate_task(rq, p, 0);
- trace_sched_wakeup_new(rq, p, 1);
+ trace_sched_wakeup_new(p, 1);
check_preempt_curr(rq, p, WF_FORK);
#ifdef CONFIG_SMP
if (p->sched_class->task_woken)
struct mm_struct *mm, *oldmm;
prepare_task_switch(rq, prev, next);
- trace_sched_switch(rq, prev, next);
+ trace_sched_switch(prev, next);
mm = next->mm;
oldmm = prev->active_mm;
/*
unsigned long avenrun[3];
EXPORT_SYMBOL(avenrun);
+static long calc_load_fold_active(struct rq *this_rq)
+{
+ long nr_active, delta = 0;
+
+ nr_active = this_rq->nr_running;
+ nr_active += (long) this_rq->nr_uninterruptible;
+
+ if (nr_active != this_rq->calc_load_active) {
+ delta = nr_active - this_rq->calc_load_active;
+ this_rq->calc_load_active = nr_active;
+ }
+
+ return delta;
+}
+
+#ifdef CONFIG_NO_HZ
+/*
+ * For NO_HZ we delay the active fold to the next LOAD_FREQ update.
+ *
+ * When making the ILB scale, we should try to pull this in as well.
+ */
+static atomic_long_t calc_load_tasks_idle;
+
+static void calc_load_account_idle(struct rq *this_rq)
+{
+ long delta;
+
+ delta = calc_load_fold_active(this_rq);
+ if (delta)
+ atomic_long_add(delta, &calc_load_tasks_idle);
+}
+
+static long calc_load_fold_idle(void)
+{
+ long delta = 0;
+
+ /*
+ * Its got a race, we don't care...
+ */
+ if (atomic_long_read(&calc_load_tasks_idle))
+ delta = atomic_long_xchg(&calc_load_tasks_idle, 0);
+
+ return delta;
+}
+#else
+static void calc_load_account_idle(struct rq *this_rq)
+{
+}
+
+static inline long calc_load_fold_idle(void)
+{
+ return 0;
+}
+#endif
+
/**
* get_avenrun - get the load average array
* @loads: pointer to dest load array
}
/*
- * Either called from update_cpu_load() or from a cpu going idle
+ * Called from update_cpu_load() to periodically update this CPU's
+ * active count.
*/
static void calc_load_account_active(struct rq *this_rq)
{
- long nr_active, delta;
+ long delta;
- nr_active = this_rq->nr_running;
- nr_active += (long) this_rq->nr_uninterruptible;
+ if (time_before(jiffies, this_rq->calc_load_update))
+ return;
- if (nr_active != this_rq->calc_load_active) {
- delta = nr_active - this_rq->calc_load_active;
- this_rq->calc_load_active = nr_active;
+ delta = calc_load_fold_active(this_rq);
+ delta += calc_load_fold_idle();
+ if (delta)
atomic_long_add(delta, &calc_load_tasks);
- }
+
+ this_rq->calc_load_update += LOAD_FREQ;
}
/*
this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) >> i;
}
- if (time_after_eq(jiffies, this_rq->calc_load_update)) {
- this_rq->calc_load_update += LOAD_FREQ;
- calc_load_account_active(this_rq);
- }
+ calc_load_account_active(this_rq);
}
#ifdef CONFIG_SMP
void sched_exec(void)
{
struct task_struct *p = current;
- struct migration_req req;
unsigned long flags;
struct rq *rq;
int dest_cpu;
* select_task_rq() can race against ->cpus_allowed
*/
if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed) &&
- likely(cpu_active(dest_cpu)) &&
- migrate_task(p, dest_cpu, &req)) {
- /* Need to wait for migration thread (might exit: take ref). */
- struct task_struct *mt = rq->migration_thread;
+ likely(cpu_active(dest_cpu)) && migrate_task(p, dest_cpu)) {
+ struct migration_arg arg = { p, dest_cpu };
- get_task_struct(mt);
task_rq_unlock(rq, &flags);
- wake_up_process(mt);
- put_task_struct(mt);
- wait_for_completion(&req.done);
-
+ stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
return;
}
unlock:
preempt_disable();
cpu = smp_processor_id();
rq = cpu_rq(cpu);
- rcu_sched_qs(cpu);
+ rcu_note_context_switch(cpu);
prev = rq->curr;
switch_count = &prev->nivcsw;
* the mutex owner just released it and exited.
*/
if (probe_kernel_address(&owner->cpu, cpu))
- goto out;
+ return 0;
#else
cpu = owner->cpu;
#endif
* the cpu field may no longer be valid.
*/
if (cpu >= nr_cpumask_bits)
- goto out;
+ return 0;
/*
* We need to validate that we can do a
* get_cpu() and that we have the percpu area.
*/
if (!cpu_online(cpu))
- goto out;
+ return 0;
rq = cpu_rq(cpu);
cpu_relax();
}
-out:
+
return 1;
}
#endif
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
- wait.flags |= WQ_FLAG_EXCLUSIVE;
- __add_wait_queue_tail(&x->wait, &wait);
+ __add_wait_queue_tail_exclusive(&x->wait, &wait);
do {
if (signal_pending_state(state, current)) {
timeout = -ERESTARTSYS;
/*
* This is how migration works:
*
- * 1) we queue a struct migration_req structure in the source CPU's
- * runqueue and wake up that CPU's migration thread.
- * 2) we down() the locked semaphore => thread blocks.
- * 3) migration thread wakes up (implicitly it forces the migrated
- * thread off the CPU)
- * 4) it gets the migration request and checks whether the migrated
- * task is still in the wrong runqueue.
- * 5) if it's in the wrong runqueue then the migration thread removes
+ * 1) we invoke migration_cpu_stop() on the target CPU using
+ * stop_one_cpu().
+ * 2) stopper starts to run (implicitly forcing the migrated thread
+ * off the CPU)
+ * 3) it checks whether the migrated task is still in the wrong runqueue.
+ * 4) if it's in the wrong runqueue then the migration thread removes
* it and puts it into the right queue.
- * 6) migration thread up()s the semaphore.
- * 7) we wake up and the migration is done.
+ * 5) stopper completes and stop_one_cpu() returns and the migration
+ * is done.
*/
/*
*/
int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
{
- struct migration_req req;
unsigned long flags;
struct rq *rq;
+ unsigned int dest_cpu;
int ret = 0;
/*
if (cpumask_test_cpu(task_cpu(p), new_mask))
goto out;
- if (migrate_task(p, cpumask_any_and(cpu_active_mask, new_mask), &req)) {
+ dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
+ if (migrate_task(p, dest_cpu)) {
+ struct migration_arg arg = { p, dest_cpu };
/* Need help from migration thread: drop lock and wait. */
- struct task_struct *mt = rq->migration_thread;
-
- get_task_struct(mt);
task_rq_unlock(rq, &flags);
- wake_up_process(mt);
- put_task_struct(mt);
- wait_for_completion(&req.done);
+ stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
tlb_migrate_finish(p->mm);
return 0;
}
return ret;
}
-#define RCU_MIGRATION_IDLE 0
-#define RCU_MIGRATION_NEED_QS 1
-#define RCU_MIGRATION_GOT_QS 2
-#define RCU_MIGRATION_MUST_SYNC 3
-
/*
- * migration_thread - this is a highprio system thread that performs
- * thread migration by bumping thread off CPU then 'pushing' onto
- * another runqueue.
+ * migration_cpu_stop - this will be executed by a highprio stopper thread
+ * and performs thread migration by bumping thread off CPU then
+ * 'pushing' onto another runqueue.
*/
-static int migration_thread(void *data)
+static int migration_cpu_stop(void *data)
{
- int badcpu;
- int cpu = (long)data;
- struct rq *rq;
-
- rq = cpu_rq(cpu);
- BUG_ON(rq->migration_thread != current);
-
- set_current_state(TASK_INTERRUPTIBLE);
- while (!kthread_should_stop()) {
- struct migration_req *req;
- struct list_head *head;
-
- raw_spin_lock_irq(&rq->lock);
-
- if (cpu_is_offline(cpu)) {
- raw_spin_unlock_irq(&rq->lock);
- break;
- }
-
- if (rq->active_balance) {
- active_load_balance(rq, cpu);
- rq->active_balance = 0;
- }
-
- head = &rq->migration_queue;
-
- if (list_empty(head)) {
- raw_spin_unlock_irq(&rq->lock);
- schedule();
- set_current_state(TASK_INTERRUPTIBLE);
- continue;
- }
- req = list_entry(head->next, struct migration_req, list);
- list_del_init(head->next);
-
- if (req->task != NULL) {
- raw_spin_unlock(&rq->lock);
- __migrate_task(req->task, cpu, req->dest_cpu);
- } else if (likely(cpu == (badcpu = smp_processor_id()))) {
- req->dest_cpu = RCU_MIGRATION_GOT_QS;
- raw_spin_unlock(&rq->lock);
- } else {
- req->dest_cpu = RCU_MIGRATION_MUST_SYNC;
- raw_spin_unlock(&rq->lock);
- WARN_ONCE(1, "migration_thread() on CPU %d, expected %d\n", badcpu, cpu);
- }
- local_irq_enable();
-
- complete(&req->done);
- }
- __set_current_state(TASK_RUNNING);
+ struct migration_arg *arg = data;
+ /*
+ * The original target cpu might have gone down and we might
+ * be on another cpu but it doesn't matter.
+ */
+ local_irq_disable();
+ __migrate_task(arg->task, raw_smp_processor_id(), arg->dest_cpu);
+ local_irq_enable();
return 0;
}
static int __cpuinit
migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
{
- struct task_struct *p;
int cpu = (long)hcpu;
unsigned long flags;
- struct rq *rq;
+ struct rq *rq = cpu_rq(cpu);
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
- p = kthread_create(migration_thread, hcpu, "migration/%d", cpu);
- if (IS_ERR(p))
- return NOTIFY_BAD;
- kthread_bind(p, cpu);
- /* Must be high prio: stop_machine expects to yield to it. */
- rq = task_rq_lock(p, &flags);
- __setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);
- task_rq_unlock(rq, &flags);
- get_task_struct(p);
- cpu_rq(cpu)->migration_thread = p;
rq->calc_load_update = calc_load_update;
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
- /* Strictly unnecessary, as first user will wake it. */
- wake_up_process(cpu_rq(cpu)->migration_thread);
-
/* Update our root-domain */
- rq = cpu_rq(cpu);
raw_spin_lock_irqsave(&rq->lock, flags);
if (rq->rd) {
BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
break;
#ifdef CONFIG_HOTPLUG_CPU
- case CPU_UP_CANCELED:
- case CPU_UP_CANCELED_FROZEN:
- if (!cpu_rq(cpu)->migration_thread)
- break;
- /* Unbind it from offline cpu so it can run. Fall thru. */
- kthread_bind(cpu_rq(cpu)->migration_thread,
- cpumask_any(cpu_online_mask));
- kthread_stop(cpu_rq(cpu)->migration_thread);
- put_task_struct(cpu_rq(cpu)->migration_thread);
- cpu_rq(cpu)->migration_thread = NULL;
- break;
-
case CPU_DEAD:
case CPU_DEAD_FROZEN:
migrate_live_tasks(cpu);
- rq = cpu_rq(cpu);
- kthread_stop(rq->migration_thread);
- put_task_struct(rq->migration_thread);
- rq->migration_thread = NULL;
/* Idle task back to normal (off runqueue, low prio) */
raw_spin_lock_irq(&rq->lock);
deactivate_task(rq, rq->idle, 0);
migrate_nr_uninterruptible(rq);
BUG_ON(rq->nr_running != 0);
calc_global_load_remove(rq);
- /*
- * No need to migrate the tasks: it was best-effort if
- * they didn't take sched_hotcpu_mutex. Just wake up
- * the requestors.
- */
- raw_spin_lock_irq(&rq->lock);
- while (!list_empty(&rq->migration_queue)) {
- struct migration_req *req;
-
- req = list_entry(rq->migration_queue.next,
- struct migration_req, list);
- list_del_init(&req->list);
- raw_spin_unlock_irq(&rq->lock);
- complete(&req->done);
- raw_spin_lock_irq(&rq->lock);
- }
- raw_spin_unlock_irq(&rq->lock);
break;
case CPU_DYING:
case CPU_DYING_FROZEN:
/* Update our root-domain */
- rq = cpu_rq(cpu);
raw_spin_lock_irqsave(&rq->lock, flags);
if (rq->rd) {
BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
struct rq *rq = cpu_rq(cpu);
struct sched_domain *tmp;
+ for (tmp = sd; tmp; tmp = tmp->parent)
+ tmp->span_weight = cpumask_weight(sched_domain_span(tmp));
+
/* Remove the sched domains which do not contribute to scheduling. */
for (tmp = sd; tmp; ) {
struct sched_domain *parent = tmp->parent;
rq->push_cpu = 0;
rq->cpu = i;
rq->online = 0;
- rq->migration_thread = NULL;
rq->idle_stamp = 0;
rq->avg_idle = 2*sysctl_sched_migration_cost;
- INIT_LIST_HEAD(&rq->migration_queue);
rq_attach_root(rq, &def_root_domain);
#endif
init_rq_hrtick(rq);
#ifndef CONFIG_SMP
-int rcu_expedited_torture_stats(char *page)
-{
- return 0;
-}
-EXPORT_SYMBOL_GPL(rcu_expedited_torture_stats);
-
void synchronize_sched_expedited(void)
{
+ barrier();
}
EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
#else /* #ifndef CONFIG_SMP */
-static DEFINE_PER_CPU(struct migration_req, rcu_migration_req);
-static DEFINE_MUTEX(rcu_sched_expedited_mutex);
-
-#define RCU_EXPEDITED_STATE_POST -2
-#define RCU_EXPEDITED_STATE_IDLE -1
-
-static int rcu_expedited_state = RCU_EXPEDITED_STATE_IDLE;
+static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0);
-int rcu_expedited_torture_stats(char *page)
+static int synchronize_sched_expedited_cpu_stop(void *data)
{
- int cnt = 0;
- int cpu;
-
- cnt += sprintf(&page[cnt], "state: %d /", rcu_expedited_state);
- for_each_online_cpu(cpu) {
- cnt += sprintf(&page[cnt], " %d:%d",
- cpu, per_cpu(rcu_migration_req, cpu).dest_cpu);
- }
- cnt += sprintf(&page[cnt], "\n");
- return cnt;
+ /*
+ * There must be a full memory barrier on each affected CPU
+ * between the time that try_stop_cpus() is called and the
+ * time that it returns.
+ *
+ * In the current initial implementation of cpu_stop, the
+ * above condition is already met when the control reaches
+ * this point and the following smp_mb() is not strictly
+ * necessary. Do smp_mb() anyway for documentation and
+ * robustness against future implementation changes.
+ */
+ smp_mb(); /* See above comment block. */
+ return 0;
}
-EXPORT_SYMBOL_GPL(rcu_expedited_torture_stats);
-
-static long synchronize_sched_expedited_count;
/*
* Wait for an rcu-sched grace period to elapse, but use "big hammer"
*/
void synchronize_sched_expedited(void)
{
- int cpu;
- unsigned long flags;
- bool need_full_sync = 0;
- struct rq *rq;
- struct migration_req *req;
- long snap;
- int trycount = 0;
+ int snap, trycount = 0;
smp_mb(); /* ensure prior mod happens before capturing snap. */
- snap = ACCESS_ONCE(synchronize_sched_expedited_count) + 1;
+ snap = atomic_read(&synchronize_sched_expedited_count) + 1;
get_online_cpus();
- while (!mutex_trylock(&rcu_sched_expedited_mutex)) {
+ while (try_stop_cpus(cpu_online_mask,
+ synchronize_sched_expedited_cpu_stop,
+ NULL) == -EAGAIN) {
put_online_cpus();
if (trycount++ < 10)
udelay(trycount * num_online_cpus());
synchronize_sched();
return;
}
- if (ACCESS_ONCE(synchronize_sched_expedited_count) - snap > 0) {
+ if (atomic_read(&synchronize_sched_expedited_count) - snap > 0) {
smp_mb(); /* ensure test happens before caller kfree */
return;
}
get_online_cpus();
}
- rcu_expedited_state = RCU_EXPEDITED_STATE_POST;
- for_each_online_cpu(cpu) {
- rq = cpu_rq(cpu);
- req = &per_cpu(rcu_migration_req, cpu);
- init_completion(&req->done);
- req->task = NULL;
- req->dest_cpu = RCU_MIGRATION_NEED_QS;
- raw_spin_lock_irqsave(&rq->lock, flags);
- list_add(&req->list, &rq->migration_queue);
- raw_spin_unlock_irqrestore(&rq->lock, flags);
- wake_up_process(rq->migration_thread);
- }
- for_each_online_cpu(cpu) {
- rcu_expedited_state = cpu;
- req = &per_cpu(rcu_migration_req, cpu);
- rq = cpu_rq(cpu);
- wait_for_completion(&req->done);
- raw_spin_lock_irqsave(&rq->lock, flags);
- if (unlikely(req->dest_cpu == RCU_MIGRATION_MUST_SYNC))
- need_full_sync = 1;
- req->dest_cpu = RCU_MIGRATION_IDLE;
- raw_spin_unlock_irqrestore(&rq->lock, flags);
- }
- rcu_expedited_state = RCU_EXPEDITED_STATE_IDLE;
- synchronize_sched_expedited_count++;
- mutex_unlock(&rcu_sched_expedited_mutex);
+ atomic_inc(&synchronize_sched_expedited_count);
+ smp_mb__after_atomic_inc(); /* ensure post-GP actions seen after GP. */
put_online_cpus();
- if (need_full_sync)
- synchronize_sched();
}
EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
git.samba.org / sfrench / cifs-2.6.git / blobdiff