9 files changed, 203 insertions, 81 deletions

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index e287863ac053..de6b1722cdca 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -48,6 +48,31 @@ extern ssize_t arch_cpu_release(const char *, size_t);
 #endif
 struct notifier_block;
 
+/*
+ * CPU notifier priorities.
+ */
+enum {
+        /*
+         * SCHED_ACTIVE marks a cpu which is coming up active during
+         * CPU_ONLINE and CPU_DOWN_FAILED and must be the first
+         * notifier.  CPUSET_ACTIVE adjusts cpuset according to
+         * cpu_active mask right after SCHED_ACTIVE.  During
+         * CPU_DOWN_PREPARE, SCHED_INACTIVE and CPUSET_INACTIVE are
+         * ordered in the similar way.
+         *
+         * This ordering guarantees consistent cpu_active mask and
+         * migration behavior to all cpu notifiers.
+         */
+        CPU_PRI_SCHED_ACTIVE    = INT_MAX,
+        CPU_PRI_CPUSET_ACTIVE   = INT_MAX - 1,
+        CPU_PRI_SCHED_INACTIVE  = INT_MIN + 1,
+        CPU_PRI_CPUSET_INACTIVE = INT_MIN,
+
+        /* migration should happen before other stuff but after perf */
+        CPU_PRI_PERF            = 20,
+        CPU_PRI_MIGRATION       = 10,
+};
+
 #ifdef CONFIG_SMP
 /* Need to know about CPUs going up/down? */
 #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE)
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 457ed765a116..f20eb8f16025 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -20,6 +20,7 @@ extern int number_of_cpusets;	/* How many cpusets are defined in system? */
 
 extern int cpuset_init(void);
 extern void cpuset_init_smp(void);
+extern void cpuset_update_active_cpus(void);
 extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
 extern int cpuset_cpus_allowed_fallback(struct task_struct *p);
 extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
@@ -132,6 +133,11 @@ static inline void set_mems_allowed(nodemask_t nodemask)
 static inline int cpuset_init(void) { return 0; }
 static inline void cpuset_init_smp(void) {}
 
+static inline void cpuset_update_active_cpus(void)
+{
+        partition_sched_domains(1, NULL, NULL);
+}
+
 static inline void cpuset_cpus_allowed(struct task_struct *p,
                                        struct cpumask *mask)
 {
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 5d0266d94985..469e03e96fe7 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1068,7 +1068,7 @@ static inline void perf_event_disable(struct perf_event *event)		{ }
 #define perf_cpu_notifier(fn)                                   \
 do {                                                            \
         static struct notifier_block fn##_nb __cpuinitdata =    \
-                { .notifier_call = fn, .priority = 20 };        \
+                { .notifier_call = fn, .priority = CPU_PRI_PERF }; \
         fn(&fn##_nb, (unsigned long)CPU_UP_PREPARE,             \
                 (void *)(unsigned long)smp_processor_id());     \
         fn(&fn##_nb, (unsigned long)CPU_STARTING,               \
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f118809c953f..edc3dd168d87 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1696,6 +1696,7 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
 #define PF_EXITING      0x00000004      /* getting shut down */
 #define PF_EXITPIDONE   0x00000008      /* pi exit done on shut down */
 #define PF_VCPU         0x00000010      /* I'm a virtual CPU */
+#define PF_WQ_WORKER    0x00000020      /* I'm a workqueue worker */
 #define PF_FORKNOEXEC   0x00000040      /* forked but didn't exec */
 #define PF_MCE_PROCESS  0x00000080      /* process policy on mce errors */
 #define PF_SUPERPRIV    0x00000100      /* used super-user privileges */
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 97d1b426a4ac..f6e726f18491 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -235,11 +235,8 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
                 return -EINVAL;
 
         cpu_hotplug_begin();
-        set_cpu_active(cpu, false);
         err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
         if (err) {
-                set_cpu_active(cpu, true);
-
                 nr_calls--;
                 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
                 printk("%s: attempt to take down CPU %u failed\n",
@@ -249,7 +246,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 
         err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
         if (err) {
-                set_cpu_active(cpu, true);
                 /* CPU didn't die: tell everyone.  Can't complain. */
                 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
 
@@ -321,8 +317,6 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
                 goto out_notify;
         BUG_ON(!cpu_online(cpu));
 
-        set_cpu_active(cpu, true);
-
         /* Now call notifier in preparation. */
         cpu_notify(CPU_ONLINE | mod, hcpu);
 
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 02b9611eadde..05727dcaa80d 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2113,31 +2113,17 @@ static void scan_for_empty_cpusets(struct cpuset *root)
  * but making no active use of cpusets.
  *
  * This routine ensures that top_cpuset.cpus_allowed tracks
- * cpu_online_map on each CPU hotplug (cpuhp) event.
+ * cpu_active_mask on each CPU hotplug (cpuhp) event.
  *
  * Called within get_online_cpus().  Needs to call cgroup_lock()
  * before calling generate_sched_domains().
  */
-static int cpuset_track_online_cpus(struct notifier_block *unused_nb,
-                                unsigned long phase, void *unused_cpu)
+void __cpuexit cpuset_update_active_cpus(void)
 {
         struct sched_domain_attr *attr;
         cpumask_var_t *doms;
         int ndoms;
 
-        switch (phase) {
-        case CPU_ONLINE:
-        case CPU_ONLINE_FROZEN:
-        case CPU_DOWN_PREPARE:
-        case CPU_DOWN_PREPARE_FROZEN:
-        case CPU_DOWN_FAILED:
-        case CPU_DOWN_FAILED_FROZEN:
-                break;
-
-        default:
-                return NOTIFY_DONE;
-        }
-
         cgroup_lock();
         mutex_lock(&callback_mutex);
         cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
@@ -2148,8 +2134,6 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb,
 
         /* Have scheduler rebuild the domains */
         partition_sched_domains(ndoms, doms, attr);
-
-        return NOTIFY_OK;
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG
@@ -2203,7 +2187,6 @@ void __init cpuset_init_smp(void)
         cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask);
         top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
 
-        hotcpu_notifier(cpuset_track_online_cpus, 0);
         hotplug_memory_notifier(cpuset_track_online_nodes, 10);
 
         cpuset_wq = create_singlethread_workqueue("cpuset");
diff --git a/kernel/fork.c b/kernel/fork.c
index b6cce14ba047..a82a65cef741 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -907,7 +907,7 @@ static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 {
         unsigned long new_flags = p->flags;
 
-        new_flags &= ~PF_SUPERPRIV;
+        new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
         new_flags |= PF_FORKNOEXEC;
         new_flags |= PF_STARTING;
         p->flags = new_flags;
diff --git a/kernel/sched.c b/kernel/sched.c
index 2aaceebd484c..8f351c56567f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -77,6 +77,7 @@
 #include <asm/irq_regs.h>
 
 #include "sched_cpupri.h"
+#include "workqueue_sched.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/sched.h>
@@ -2264,11 +2265,55 @@ static void update_avg(u64 *avg, u64 sample)
 }
 #endif
 
-/***
+static inline void ttwu_activate(struct task_struct *p, struct rq *rq,
+                                 bool is_sync, bool is_migrate, bool is_local,
+                                 unsigned long en_flags)
+{
+        schedstat_inc(p, se.statistics.nr_wakeups);
+        if (is_sync)
+                schedstat_inc(p, se.statistics.nr_wakeups_sync);
+        if (is_migrate)
+                schedstat_inc(p, se.statistics.nr_wakeups_migrate);
+        if (is_local)
+                schedstat_inc(p, se.statistics.nr_wakeups_local);
+        else
+                schedstat_inc(p, se.statistics.nr_wakeups_remote);
+
+        activate_task(rq, p, en_flags);
+}
+
+static inline void ttwu_post_activation(struct task_struct *p, struct rq *rq,
+                                        int wake_flags, bool success)
+{
+        trace_sched_wakeup(p, success);
+        check_preempt_curr(rq, p, wake_flags);
+
+        p->state = TASK_RUNNING;
+#ifdef CONFIG_SMP
+        if (p->sched_class->task_woken)
+                p->sched_class->task_woken(rq, p);
+
+        if (unlikely(rq->idle_stamp)) {
+                u64 delta = rq->clock - rq->idle_stamp;
+                u64 max = 2*sysctl_sched_migration_cost;
+
+                if (delta > max)
+                        rq->avg_idle = max;
+                else
+                        update_avg(&rq->avg_idle, delta);
+                rq->idle_stamp = 0;
+        }
+#endif
+        /* if a worker is waking up, notify workqueue */
+        if ((p->flags & PF_WQ_WORKER) && success)
+                wq_worker_waking_up(p, cpu_of(rq));
+}
+
+/**
  * try_to_wake_up - wake up a thread
- * @p: the to-be-woken-up thread
+ * @p: the thread to be awakened
  * @state: the mask of task states that can be woken
- * @sync: do a synchronous wakeup?
+ * @wake_flags: wake modifier flags (WF_*)
  *
  * Put it on the run-queue if it's not already there. The "current"
  * thread is always on the run-queue (except when the actual
@@ -2276,7 +2321,8 @@ static void update_avg(u64 *avg, u64 sample)
  * the simpler "current->state = TASK_RUNNING" to mark yourself
  * runnable without the overhead of this.
  *
- * returns failure only if the task is already active.
+ * Returns %true if @p was woken up, %false if it was already running
+ * or @state didn't match @p's state.
  */
 static int try_to_wake_up(struct task_struct *p, unsigned int state,
                           int wake_flags)
@@ -2356,38 +2402,11 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state,
 
 out_activate:
 #endif /* CONFIG_SMP */
-        schedstat_inc(p, se.statistics.nr_wakeups);
-        if (wake_flags & WF_SYNC)
-                schedstat_inc(p, se.statistics.nr_wakeups_sync);
-        if (orig_cpu != cpu)
-                schedstat_inc(p, se.statistics.nr_wakeups_migrate);
-        if (cpu == this_cpu)
-                schedstat_inc(p, se.statistics.nr_wakeups_local);
-        else
-                schedstat_inc(p, se.statistics.nr_wakeups_remote);
-        activate_task(rq, p, en_flags);
+        ttwu_activate(p, rq, wake_flags & WF_SYNC, orig_cpu != cpu,
+                      cpu == this_cpu, en_flags);
         success = 1;
-
 out_running:
-        trace_sched_wakeup(p, success);
-        check_preempt_curr(rq, p, wake_flags);
-
-        p->state = TASK_RUNNING;
-#ifdef CONFIG_SMP
-        if (p->sched_class->task_woken)
-                p->sched_class->task_woken(rq, p);
-
-        if (unlikely(rq->idle_stamp)) {
-                u64 delta = rq->clock - rq->idle_stamp;
-                u64 max = 2*sysctl_sched_migration_cost;
-
-                if (delta > max)
-                        rq->avg_idle = max;
-                else
-                        update_avg(&rq->avg_idle, delta);
-                rq->idle_stamp = 0;
-        }
-#endif
+        ttwu_post_activation(p, rq, wake_flags, success);
 out:
         task_rq_unlock(rq, &flags);
         put_cpu();
@@ -2396,6 +2415,37 @@ out:
 }
 
 /**
+ * try_to_wake_up_local - try to wake up a local task with rq lock held
+ * @p: the thread to be awakened
+ *
+ * Put @p on the run-queue if it's not alredy there.  The caller must
+ * ensure that this_rq() is locked, @p is bound to this_rq() and not
+ * the current task.  this_rq() stays locked over invocation.
+ */
+static void try_to_wake_up_local(struct task_struct *p)
+{
+        struct rq *rq = task_rq(p);
+        bool success = false;
+
+        BUG_ON(rq != this_rq());
+        BUG_ON(p == current);
+        lockdep_assert_held(&rq->lock);
+
+        if (!(p->state & TASK_NORMAL))
+                return;
+
+        if (!p->se.on_rq) {
+                if (likely(!task_running(rq, p))) {
+                        schedstat_inc(rq, ttwu_count);
+                        schedstat_inc(rq, ttwu_local);
+                }
+                ttwu_activate(p, rq, false, false, true, ENQUEUE_WAKEUP);
+                success = true;
+        }
+        ttwu_post_activation(p, rq, 0, success);
+}
+
+/**
  * wake_up_process - Wake up a specific process
  * @p: The process to be woken up.
  *
@@ -3600,10 +3650,24 @@ need_resched_nonpreemptible:
         clear_tsk_need_resched(prev);
 
         if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
-                if (unlikely(signal_pending_state(prev->state, prev)))
+                if (unlikely(signal_pending_state(prev->state, prev))) {
                         prev->state = TASK_RUNNING;
-                else
+                } else {
+                        /*
+                         * If a worker is going to sleep, notify and
+                         * ask workqueue whether it wants to wake up a
+                         * task to maintain concurrency.  If so, wake
+                         * up the task.
+                         */
+                        if (prev->flags & PF_WQ_WORKER) {
+                                struct task_struct *to_wakeup;
+
+                                to_wakeup = wq_worker_sleeping(prev, cpu);
+                                if (to_wakeup)
+                                        try_to_wake_up_local(to_wakeup);
+                        }
                         deactivate_task(rq, prev, DEQUEUE_SLEEP);
+                }
                 switch_count = &prev->nvcsw;
         }
 
@@ -5804,20 +5868,49 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
  */
 static struct notifier_block __cpuinitdata migration_notifier = {
         .notifier_call = migration_call,
-        .priority = 10
+        .priority = CPU_PRI_MIGRATION,
 };
 
+static int __cpuinit sched_cpu_active(struct notifier_block *nfb,
+                                      unsigned long action, void *hcpu)
+{
+        switch (action & ~CPU_TASKS_FROZEN) {
+        case CPU_ONLINE:
+        case CPU_DOWN_FAILED:
+                set_cpu_active((long)hcpu, true);
+                return NOTIFY_OK;
+        default:
+                return NOTIFY_DONE;
+        }
+}
+
+static int __cpuinit sched_cpu_inactive(struct notifier_block *nfb,
+                                        unsigned long action, void *hcpu)
+{
+        switch (action & ~CPU_TASKS_FROZEN) {
+        case CPU_DOWN_PREPARE:
+                set_cpu_active((long)hcpu, false);
+                return NOTIFY_OK;
+        default:
+                return NOTIFY_DONE;
+        }
+}
+
 static int __init migration_init(void)
 {
         void *cpu = (void *)(long)smp_processor_id();
         int err;
 
-        /* Start one for the boot CPU: */
+        /* Initialize migration for the boot CPU */
         err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
         BUG_ON(err == NOTIFY_BAD);
         migration_call(&migration_notifier, CPU_ONLINE, cpu);
         register_cpu_notifier(&migration_notifier);
 
+        /* Register cpu active notifiers */
+        cpu_notifier(sched_cpu_active, CPU_PRI_SCHED_ACTIVE);
+        cpu_notifier(sched_cpu_inactive, CPU_PRI_SCHED_INACTIVE);
+
         return 0;
 }
 early_initcall(migration_init);
@@ -7276,29 +7369,35 @@ int __init sched_create_sysfs_power_savings_entries(struct sysdev_class *cls)
 }
 #endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
 
-#ifndef CONFIG_CPUSETS
 /*
- * Add online and remove offline CPUs from the scheduler domains.
- * When cpusets are enabled they take over this function.
+ * Update cpusets according to cpu_active mask.  If cpusets are
+ * disabled, cpuset_update_active_cpus() becomes a simple wrapper
+ * around partition_sched_domains().
  */
-static int update_sched_domains(struct notifier_block *nfb,
-                                unsigned long action, void *hcpu)
+static int __cpuexit cpuset_cpu_active(struct notifier_block *nfb,
+                                       unsigned long action, void *hcpu)
 {
-        switch (action) {
+        switch (action & ~CPU_TASKS_FROZEN) {
         case CPU_ONLINE:
-        case CPU_ONLINE_FROZEN:
-        case CPU_DOWN_PREPARE:
-        case CPU_DOWN_PREPARE_FROZEN:
         case CPU_DOWN_FAILED:
-        case CPU_DOWN_FAILED_FROZEN:
-                partition_sched_domains(1, NULL, NULL);
+                cpuset_update_active_cpus();
                 return NOTIFY_OK;
+        default:
+                return NOTIFY_DONE;
+        }
+}
 
+static int __cpuexit cpuset_cpu_inactive(struct notifier_block *nfb,
+                                         unsigned long action, void *hcpu)
+{
+        switch (action & ~CPU_TASKS_FROZEN) {
+        case CPU_DOWN_PREPARE:
+                cpuset_update_active_cpus();
+                return NOTIFY_OK;
         default:
                 return NOTIFY_DONE;
         }
 }
-#endif
 
 static int update_runtime(struct notifier_block *nfb,
                                 unsigned long action, void *hcpu)
@@ -7344,10 +7443,8 @@ void __init sched_init_smp(void)
         mutex_unlock(&sched_domains_mutex);
         put_online_cpus();
 
-#ifndef CONFIG_CPUSETS
-        /* XXX: Theoretical race here - CPU may be hotplugged now */
-        hotcpu_notifier(update_sched_domains, 0);
-#endif
+        hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
+        hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);
 
         /* RT runtime code needs to handle some hotplug events */
         hotcpu_notifier(update_runtime, 0);
diff --git a/kernel/workqueue_sched.h b/kernel/workqueue_sched.h
new file mode 100644
index 000000000000..af040babb742
--- /dev/null
+++ b/kernel/workqueue_sched.h
@@ -0,0 +1,16 @@
+/*
+ * kernel/workqueue_sched.h
+ *
+ * Scheduler hooks for concurrency managed workqueue.  Only to be
+ * included from sched.c and workqueue.c.
+ */
+static inline void wq_worker_waking_up(struct task_struct *task,
+                                       unsigned int cpu)
+{
+}
+
+static inline struct task_struct *wq_worker_sleeping(struct task_struct *task,
+                                                     unsigned int cpu)
+{
+        return NULL;
+}