summaryrefslogtreecommitdiffstats
path: root/kernel/sched
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/core.c39
1 files changed, 35 insertions, 4 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 16946b55e8e7..56b09628692a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1796,13 +1796,28 @@ static inline bool rq_has_pinned_tasks(struct rq *rq)
*/
static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
{
+ /* When not in the task's cpumask, no point in looking further. */
if (!cpumask_test_cpu(cpu, p->cpus_ptr))
return false;
- if (is_per_cpu_kthread(p) || is_migration_disabled(p))
+ /* migrate_disabled() must be allowed to finish. */
+ if (is_migration_disabled(p))
return cpu_online(cpu);
- return cpu_active(cpu);
+ /* Non kernel threads are not allowed during either online or offline. */
+ if (!(p->flags & PF_KTHREAD))
+ return cpu_active(cpu);
+
+ /* KTHREAD_IS_PER_CPU is always allowed. */
+ if (kthread_is_per_cpu(p))
+ return cpu_online(cpu);
+
+ /* Regular kernel threads don't get to stay during offline. */
+ if (cpu_rq(cpu)->balance_push)
+ return false;
+
+ /* But are allowed during online. */
+ return cpu_online(cpu);
}
/*
@@ -3122,6 +3137,13 @@ bool cpus_share_cache(int this_cpu, int that_cpu)
static inline bool ttwu_queue_cond(int cpu, int wake_flags)
{
/*
+ * Do not complicate things with the async wake_list while the CPU is
+ * in hotplug state.
+ */
+ if (!cpu_active(cpu))
+ return false;
+
+ /*
* If the CPU does not share cache, then queue the task on the
* remote rqs wakelist to avoid accessing remote data.
*/
@@ -7276,8 +7298,14 @@ static void balance_push(struct rq *rq)
/*
* Both the cpu-hotplug and stop task are in this case and are
* required to complete the hotplug process.
+ *
+ * XXX: the idle task does not match kthread_is_per_cpu() due to
+ * histerical raisins.
*/
- if (is_per_cpu_kthread(push_task) || is_migration_disabled(push_task)) {
+ if (rq->idle == push_task ||
+ ((push_task->flags & PF_KTHREAD) && kthread_is_per_cpu(push_task)) ||
+ is_migration_disabled(push_task)) {
+
/*
* If this is the idle task on the outgoing CPU try to wake
* up the hotplug control thread which might wait for the
@@ -7309,7 +7337,7 @@ static void balance_push(struct rq *rq)
/*
* At this point need_resched() is true and we'll take the loop in
* schedule(). The next pick is obviously going to be the stop task
- * which is_per_cpu_kthread() and will push this task away.
+ * which kthread_is_per_cpu() and will push this task away.
*/
raw_spin_lock(&rq->lock);
}
@@ -7497,6 +7525,9 @@ int sched_cpu_deactivate(unsigned int cpu)
* preempt-disabled and RCU users of this state to go away such that
* all new such users will observe it.
*
+ * Specifically, we rely on ttwu to no longer target this CPU, see
+ * ttwu_queue_cond() and is_cpu_allowed().
+ *
* Do sync before park smpboot threads to take care the rcu boost case.
*/
synchronize_rcu();