Merge tag 'mfd-fixes-4.3' of git://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd

[karo-tx-linux.git] / kernel / sched / core.c

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2f9c9288481779c309f31c19dc3b74831ef70b3d..10a8faa1b0d4a5f737bd9008eb8f9a7e817b6ec9 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2517,11 +2517,11 @@ static struct rq *finish_task_switch(struct task_struct *prev)
         * If a task dies, then it sets TASK_DEAD in tsk->state and calls
         * schedule one last time. The schedule call will never return, and
         * the scheduled task must drop that reference.
-        * The test for TASK_DEAD must occur while the runqueue locks are
-        * still held, otherwise prev could be scheduled on another cpu, die
-        * there before we look at prev->state, and then the reference would
-        * be dropped twice.
-        *              Manfred Spraul <manfred@colorfullife.com>
+        *
+        * We must observe prev->state before clearing prev->on_cpu (in
+        * finish_lock_switch), otherwise a concurrent wakeup can get prev
+        * running on another CPU and we could rave with its RUNNING -> DEAD
+        * transition, resulting in a double drop.
         */
        prev_state = prev->state;
        vtime_task_switch(prev);
@@ -4934,7 +4934,15 @@ void init_idle(struct task_struct *idle, int cpu)
        idle->state = TASK_RUNNING;
        idle->se.exec_start = sched_clock();
 
-       do_set_cpus_allowed(idle, cpumask_of(cpu));
+#ifdef CONFIG_SMP
+       /*
+        * Its possible that init_idle() gets called multiple times on a task,
+        * in that case do_set_cpus_allowed() will not do the right thing.
+        *
+        * And since this is boot we can forgo the serialization.
+        */
+       set_cpus_allowed_common(idle, cpumask_of(cpu));
+#endif
        /*
         * We're having a chicken and egg problem, even though we are
         * holding rq->lock, the cpu isn't yet set to this cpu so the
@@ -4951,7 +4959,7 @@ void init_idle(struct task_struct *idle, int cpu)
 
        rq->curr = rq->idle = idle;
        idle->on_rq = TASK_ON_RQ_QUEUED;
-#if defined(CONFIG_SMP)
+#ifdef CONFIG_SMP
        idle->on_cpu = 1;
 #endif
        raw_spin_unlock(&rq->lock);
@@ -4966,7 +4974,7 @@ void init_idle(struct task_struct *idle, int cpu)
        idle->sched_class = &idle_sched_class;
        ftrace_graph_init_idle_task(idle, cpu);
        vtime_init_idle(idle, cpu);
-#if defined(CONFIG_SMP)
+#ifdef CONFIG_SMP
        sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
 #endif
 }