Merge branch 'master' into for-4.4-fixes

[firefly-linux-kernel-4.4.55.git] / kernel / sched / core.c

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a9db4819e58606f11cb35768fe8f727e85425c14..732e993b564b8179e5723bb88839329eec6df8f5 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1946,6 +1946,25 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
                goto stat;
 
 #ifdef CONFIG_SMP
+       /*
+        * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
+        * possible to, falsely, observe p->on_cpu == 0.
+        *
+        * One must be running (->on_cpu == 1) in order to remove oneself
+        * from the runqueue.
+        *
+        *  [S] ->on_cpu = 1;   [L] ->on_rq
+        *      UNLOCK rq->lock
+        *                      RMB
+        *      LOCK   rq->lock
+        *  [S] ->on_rq = 0;    [L] ->on_cpu
+        *
+        * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock
+        * from the consecutive calls to schedule(); the first switching to our
+        * task, the second putting it to sleep.
+        */
+       smp_rmb();
+
        /*
         * If the owning (remote) cpu is still in the middle of schedule() with
         * this task as prev, wait until its done referencing the task.
@@ -1953,7 +1972,13 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
        while (p->on_cpu)
                cpu_relax();
        /*
-        * Pairs with the smp_wmb() in finish_lock_switch().
+        * Combined with the control dependency above, we have an effective
+        * smp_load_acquire() without the need for full barriers.
+        *
+        * Pairs with the smp_store_release() in finish_lock_switch().
+        *
+        * This ensures that tasks getting woken will be fully ordered against
+        * their previous state and preserve Program Order.
         */
        smp_rmb();
 
@@ -2039,7 +2064,6 @@ out:
  */
 int wake_up_process(struct task_struct *p)
 {
-       WARN_ON(task_is_stopped_or_traced(p));
        return try_to_wake_up(p, TASK_NORMAL, 0);
 }
 EXPORT_SYMBOL(wake_up_process);
@@ -5847,13 +5871,13 @@ static int init_rootdomain(struct root_domain *rd)
 {
        memset(rd, 0, sizeof(*rd));
 
-       if (!alloc_cpumask_var(&rd->span, GFP_KERNEL))
+       if (!zalloc_cpumask_var(&rd->span, GFP_KERNEL))
                goto out;
-       if (!alloc_cpumask_var(&rd->online, GFP_KERNEL))
+       if (!zalloc_cpumask_var(&rd->online, GFP_KERNEL))
                goto free_span;
-       if (!alloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
+       if (!zalloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))
                goto free_online;
-       if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
+       if (!zalloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
                goto free_dlo_mask;
 
        init_dl_bw(&rd->dl_bw);