Linux-libre 4.8.2-gnupck-4.8.2-gnu

1 files changed, 104 insertions, 37 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 38eacc323..44817c640 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -74,6 +74,7 @@
 #include <linux/context_tracking.h>
 #include <linux/compiler.h>
 #include <linux/frame.h>
+#include <linux/prefetch.h>
 
 #include <asm/switch_to.h>
 #include <asm/tlb.h>
@@ -1937,7 +1938,7 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
  * chain to provide order. Instead we do:
  *
  *   1) smp_store_release(X->on_cpu, 0)
- *   2) smp_cond_acquire(!X->on_cpu)
+ *   2) smp_cond_load_acquire(!X->on_cpu)
  *
  * Example:
  *
@@ -1948,7 +1949,7 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
  *   sched-out X
  *   smp_store_release(X->on_cpu, 0);
  *
- *                    smp_cond_acquire(!X->on_cpu);
+ *                    smp_cond_load_acquire(&X->on_cpu, !VAL);
  *                    X->state = WAKING
  *                    set_task_cpu(X,2)
  *
@@ -1974,7 +1975,7 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
  * This means that any means of doing remote wakeups must order the CPU doing
  * the wakeup against the CPU the task is going to end up running on. This,
  * however, is already required for the regular Program-Order guarantee above,
- * since the waking CPU is the one issueing the ACQUIRE (smp_cond_acquire).
+ * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire).
  *
  */
 
@@ -2069,7 +2070,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 	 * This ensures that tasks getting woken will be fully ordered against
 	 * their previous state and preserve Program Order.
 	 */
-	smp_cond_acquire(!p->on_cpu);
+	smp_cond_load_acquire(&p->on_cpu, !VAL);
 
 	p->sched_contributes_to_load = !!task_contributes_to_load(p);
 	p->state = TASK_WAKING;
@@ -2364,11 +2365,11 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 
 	__sched_fork(clone_flags, p);
 	/*
-	 * We mark the process as running here. This guarantees that
+	 * We mark the process as NEW here. This guarantees that
 	 * nobody will actually run it, and a signal or other external
 	 * event cannot wake it up and insert it on the runqueue either.
 	 */
-	p->state = TASK_RUNNING;
+	p->state = TASK_NEW;
 
 	/*
 	 * Make sure we do not leak PI boosting priority to the child.
@@ -2405,8 +2406,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 		p->sched_class = &fair_sched_class;
 	}
 
-	if (p->sched_class->task_fork)
-		p->sched_class->task_fork(p);
+	init_entity_runnable_average(&p->se);
 
 	/*
 	 * The child is not yet in the pid-hash so no cgroup attach races,
@@ -2416,7 +2416,13 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 	 * Silence PROVE_RCU.
 	 */
 	raw_spin_lock_irqsave(&p->pi_lock, flags);
-	set_task_cpu(p, cpu);
+	/*
+	 * We're setting the cpu for the first time, we don't migrate,
+	 * so use __set_task_cpu().
+	 */
+	__set_task_cpu(p, cpu);
+	if (p->sched_class->task_fork)
+		p->sched_class->task_fork(p);
 	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
 
 #ifdef CONFIG_SCHED_INFO
@@ -2548,16 +2554,18 @@ void wake_up_new_task(struct task_struct *p)
 	struct rq_flags rf;
 	struct rq *rq;
 
-	/* Initialize new task's runnable average */
-	init_entity_runnable_average(&p->se);
 	raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
+	p->state = TASK_RUNNING;
 #ifdef CONFIG_SMP
 	/*
 	 * Fork balancing, do it here and not earlier because:
 	 *  - cpus_allowed can change in the fork path
 	 *  - any previously selected cpu might disappear through hotplug
+	 *
+	 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
+	 * as we're not fully set-up yet.
 	 */
-	set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
+	__set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
 #endif
 	rq = __task_rq_lock(p, &rf);
 	post_init_entity_util_avg(&p->se);
@@ -2987,6 +2995,23 @@ EXPORT_PER_CPU_SYMBOL(kstat);
 EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
 
 /*
+ * The function fair_sched_class.update_curr accesses the struct curr
+ * and its field curr->exec_start; when called from task_sched_runtime(),
+ * we observe a high rate of cache misses in practice.
+ * Prefetching this data results in improved performance.
+ */
+static inline void prefetch_curr_exec_start(struct task_struct *p)
+{
+#ifdef CONFIG_FAIR_GROUP_SCHED
+	struct sched_entity *curr = (&p->se)->cfs_rq->curr;
+#else
+	struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
+#endif
+	prefetch(curr);
+	prefetch(&curr->exec_start);
+}
+
+/*
  * Return accounted runtime for the task.
  * In case the task is currently running, return the runtime plus current's
  * pending runtime that have not been accounted yet.
@@ -3020,6 +3045,7 @@ unsigned long long task_sched_runtime(struct task_struct *p)
 	 * thread, breaking clock_gettime().
 	 */
 	if (task_current(rq, p) && task_on_rq_queued(p)) {
+		prefetch_curr_exec_start(p);
 		update_rq_clock(rq);
 		p->sched_class->update_curr(rq);
 	}
@@ -3183,6 +3209,9 @@ static noinline void __schedule_bug(struct task_struct *prev)
 		pr_cont("\n");
 	}
 #endif
+	if (panic_on_warn)
+		panic("scheduling while atomic\n");
+
 	dump_stack();
 	add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
 }
@@ -4774,7 +4803,8 @@ out_unlock:
  * @len: length in bytes of the bitmask pointed to by user_mask_ptr
  * @user_mask_ptr: user-space pointer to hold the current cpu mask
  *
- * Return: 0 on success. An error code otherwise.
+ * Return: size of CPU mask copied to user_mask_ptr on success. An
+ * error code otherwise.
  */
 SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
 		unsigned long __user *, user_mask_ptr)
@@ -7255,7 +7285,6 @@ static void sched_rq_cpu_starting(unsigned int cpu)
 	struct rq *rq = cpu_rq(cpu);
 
 	rq->calc_load_update = calc_load_update;
-	account_reset_rq(rq);
 	update_max_interval();
 }
 
@@ -7735,6 +7764,8 @@ void sched_online_group(struct task_group *tg, struct task_group *parent)
 	INIT_LIST_HEAD(&tg->children);
 	list_add_rcu(&tg->siblings, &parent->children);
 	spin_unlock_irqrestore(&task_group_lock, flags);
+
+	online_fair_sched_group(tg);
 }
 
 /* rcu callback to free various structures associated with a task group */
@@ -7763,27 +7794,9 @@ void sched_offline_group(struct task_group *tg)
 	spin_unlock_irqrestore(&task_group_lock, flags);
 }
 
-/* change task's runqueue when it moves between groups.
- *	The caller of this function should have put the task in its new group
- *	by now. This function just updates tsk->se.cfs_rq and tsk->se.parent to
- *	reflect its new group.
- */
-void sched_move_task(struct task_struct *tsk)
+static void sched_change_group(struct task_struct *tsk, int type)
 {
 	struct task_group *tg;
-	int queued, running;
-	struct rq_flags rf;
-	struct rq *rq;
-
-	rq = task_rq_lock(tsk, &rf);
-
-	running = task_current(rq, tsk);
-	queued = task_on_rq_queued(tsk);
-
-	if (queued)
-		dequeue_task(rq, tsk, DEQUEUE_SAVE | DEQUEUE_MOVE);
-	if (unlikely(running))
-		put_prev_task(rq, tsk);
 
 	/*
 	 * All callers are synchronized by task_rq_lock(); we do not use RCU
@@ -7796,11 +7809,37 @@ void sched_move_task(struct task_struct *tsk)
 	tsk->sched_task_group = tg;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
-	if (tsk->sched_class->task_move_group)
-		tsk->sched_class->task_move_group(tsk);
+	if (tsk->sched_class->task_change_group)
+		tsk->sched_class->task_change_group(tsk, type);
 	else
 #endif
 		set_task_rq(tsk, task_cpu(tsk));
+}
+
+/*
+ * Change task's runqueue when it moves between groups.
+ *
+ * The caller of this function should have put the task in its new group by
+ * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
+ * its new group.
+ */
+void sched_move_task(struct task_struct *tsk)
+{
+	int queued, running;
+	struct rq_flags rf;
+	struct rq *rq;
+
+	rq = task_rq_lock(tsk, &rf);
+
+	running = task_current(rq, tsk);
+	queued = task_on_rq_queued(tsk);
+
+	if (queued)
+		dequeue_task(rq, tsk, DEQUEUE_SAVE | DEQUEUE_MOVE);
+	if (unlikely(running))
+		put_prev_task(rq, tsk);
+
+	sched_change_group(tsk, TASK_MOVE_GROUP);
 
 	if (unlikely(running))
 		tsk->sched_class->set_curr_task(rq);
@@ -8228,15 +8267,27 @@ static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
 	sched_free_group(tg);
 }
 
+/*
+ * This is called before wake_up_new_task(), therefore we really only
+ * have to set its group bits, all the other stuff does not apply.
+ */
 static void cpu_cgroup_fork(struct task_struct *task)
 {
-	sched_move_task(task);
+	struct rq_flags rf;
+	struct rq *rq;
+
+	rq = task_rq_lock(task, &rf);
+
+	sched_change_group(task, TASK_SET_GROUP);
+
+	task_rq_unlock(rq, task, &rf);
 }
 
 static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
 {
 	struct task_struct *task;
 	struct cgroup_subsys_state *css;
+	int ret = 0;
 
 	cgroup_taskset_for_each(task, css, tset) {
 #ifdef CONFIG_RT_GROUP_SCHED
@@ -8247,8 +8298,24 @@ static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
 		if (task->sched_class != &fair_sched_class)
 			return -EINVAL;
 #endif
+		/*
+		 * Serialize against wake_up_new_task() such that if its
+		 * running, we're sure to observe its full state.
+		 */
+		raw_spin_lock_irq(&task->pi_lock);
+		/*
+		 * Avoid calling sched_move_task() before wake_up_new_task()
+		 * has happened. This would lead to problems with PELT, due to
+		 * move wanting to detach+attach while we're not attached yet.
+		 */
+		if (task->state == TASK_NEW)
+			ret = -EINVAL;
+		raw_spin_unlock_irq(&task->pi_lock);
+
+		if (ret)
+			break;
 	}
-	return 0;
+	return ret;
 }
 
 static void cpu_cgroup_attach(struct cgroup_taskset *tset)