Merge branch 'next' into for-linus

Second round of updates for 3.20.

1 files changed, 33 insertions, 8 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c0accc00566e..5eab11d4b747 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1814,6 +1814,10 @@ void __dl_clear_params(struct task_struct *p)
         dl_se->dl_period = 0;
         dl_se->flags = 0;
         dl_se->dl_bw = 0;
+
+        dl_se->dl_throttled = 0;
+        dl_se->dl_new = 1;
+        dl_se->dl_yielded = 0;
 }
 
 /*
@@ -1839,7 +1843,7 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
 #endif
 
         RB_CLEAR_NODE(&p->dl.rb_node);
-        hrtimer_init(&p->dl.dl_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+        init_dl_task_timer(&p->dl);
         __dl_clear_params(p);
 
         INIT_LIST_HEAD(&p->rt.run_list);
@@ -2049,6 +2053,9 @@ static inline int dl_bw_cpus(int i)
  * allocated bandwidth to reflect the new situation.
  *
  * This function is called while holding p's rq->lock.
+ *
+ * XXX we should delay bw change until the task's 0-lag point, see
+ * __setparam_dl().
  */
 static int dl_overflow(struct task_struct *p, int policy,
                        const struct sched_attr *attr)
@@ -3251,15 +3258,31 @@ __setparam_dl(struct task_struct *p, const struct sched_attr *attr)
 {
         struct sched_dl_entity *dl_se = &p->dl;
 
-        init_dl_task_timer(dl_se);
         dl_se->dl_runtime = attr->sched_runtime;
         dl_se->dl_deadline = attr->sched_deadline;
         dl_se->dl_period = attr->sched_period ?: dl_se->dl_deadline;
         dl_se->flags = attr->sched_flags;
         dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime);
-        dl_se->dl_throttled = 0;
-        dl_se->dl_new = 1;
-        dl_se->dl_yielded = 0;
+
+        /*
+         * Changing the parameters of a task is 'tricky' and we're not doing
+         * the correct thing -- also see task_dead_dl() and switched_from_dl().
+         *
+         * What we SHOULD do is delay the bandwidth release until the 0-lag
+         * point. This would include retaining the task_struct until that time
+         * and change dl_overflow() to not immediately decrement the current
+         * amount.
+         *
+         * Instead we retain the current runtime/deadline and let the new
+         * parameters take effect after the current reservation period lapses.
+         * This is safe (albeit pessimistic) because the 0-lag point is always
+         * before the current scheduling deadline.
+         *
+         * We can still have temporary overloads because we do not delay the
+         * change in bandwidth until that time; so admission control is
+         * not on the safe side. It does however guarantee tasks will never
+         * consume more than promised.
+         */
 }
 
 /*
@@ -4642,6 +4665,9 @@ int cpuset_cpumask_can_shrink(const struct cpumask *cur,
         struct dl_bw *cur_dl_b;
         unsigned long flags;
 
+        if (!cpumask_weight(cur))
+                return ret;
+
         rcu_read_lock_sched();
         cur_dl_b = dl_bw_of(cpumask_any(cur));
         trial_cpus = cpumask_weight(trial);
@@ -7292,13 +7318,12 @@ void __might_sleep(const char *file, int line, int preempt_offset)
          * since we will exit with TASK_RUNNING make sure we enter with it,
          * otherwise we will destroy state.
          */
-        if (WARN_ONCE(current->state != TASK_RUNNING,
+        WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
                         "do not call blocking ops when !TASK_RUNNING; "
                         "state=%lx set at [<%p>] %pS\n",
                         current->state,
                         (void *)current->task_state_change,
-                        (void *)current->task_state_change))
-                __set_current_state(TASK_RUNNING);
+                        (void *)current->task_state_change);
 
         ___might_sleep(file, line, preempt_offset);
 }