summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--kernel/sched/core.c54
-rw-r--r--kernel/sched/idle.c10
-rw-r--r--kernel/sched/sched.h6
3 files changed, 61 insertions, 9 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6afbfeefddd6..60d4e05d64dd 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -519,7 +519,7 @@ static inline void init_hrtick(void)
__old; \
})
-#ifdef TIF_POLLING_NRFLAG
+#if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
/*
* Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
* this avoids any races wrt polling state changes and thereby avoids
@@ -530,12 +530,44 @@ static bool set_nr_and_not_polling(struct task_struct *p)
struct thread_info *ti = task_thread_info(p);
return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
}
+
+/*
+ * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
+ *
+ * If this returns true, then the idle task promises to call
+ * sched_ttwu_pending() and reschedule soon.
+ */
+static bool set_nr_if_polling(struct task_struct *p)
+{
+ struct thread_info *ti = task_thread_info(p);
+ typeof(ti->flags) old, val = ACCESS_ONCE(ti->flags);
+
+ for (;;) {
+ if (!(val & _TIF_POLLING_NRFLAG))
+ return false;
+ if (val & _TIF_NEED_RESCHED)
+ return true;
+ old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
+ if (old == val)
+ break;
+ val = old;
+ }
+ return true;
+}
+
#else
static bool set_nr_and_not_polling(struct task_struct *p)
{
set_tsk_need_resched(p);
return true;
}
+
+#ifdef CONFIG_SMP
+static bool set_nr_if_polling(struct task_struct *p)
+{
+ return false;
+}
+#endif
#endif
/*
@@ -1490,13 +1522,17 @@ static int ttwu_remote(struct task_struct *p, int wake_flags)
}
#ifdef CONFIG_SMP
-static void sched_ttwu_pending(void)
+void sched_ttwu_pending(void)
{
struct rq *rq = this_rq();
struct llist_node *llist = llist_del_all(&rq->wake_list);
struct task_struct *p;
+ unsigned long flags;
- raw_spin_lock(&rq->lock);
+ if (!llist)
+ return;
+
+ raw_spin_lock_irqsave(&rq->lock, flags);
while (llist) {
p = llist_entry(llist, struct task_struct, wake_entry);
@@ -1504,7 +1540,7 @@ static void sched_ttwu_pending(void)
ttwu_do_activate(rq, p, 0);
}
- raw_spin_unlock(&rq->lock);
+ raw_spin_unlock_irqrestore(&rq->lock, flags);
}
void scheduler_ipi(void)
@@ -1550,8 +1586,14 @@ void scheduler_ipi(void)
static void ttwu_queue_remote(struct task_struct *p, int cpu)
{
- if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list))
- smp_send_reschedule(cpu);
+ struct rq *rq = cpu_rq(cpu);
+
+ if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
+ if (!set_nr_if_polling(rq->idle))
+ smp_send_reschedule(cpu);
+ else
+ trace_sched_wake_idle_without_ipi(cpu);
+ }
}
bool cpus_share_cache(int this_cpu, int that_cpu)
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index fe4b24bf33ca..cf009fb0bc25 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -12,6 +12,8 @@
#include <trace/events/power.h>
+#include "sched.h"
+
static int __read_mostly cpu_idle_force_poll;
void cpu_idle_poll_ctrl(bool enable)
@@ -237,12 +239,14 @@ static void cpu_idle_loop(void)
__current_clr_polling();
/*
- * We promise to reschedule if need_resched is set while
- * polling is set. That means that clearing polling
- * needs to be visible before rescheduling.
+ * We promise to call sched_ttwu_pending and reschedule
+ * if need_resched is set while polling is set. That
+ * means that clearing polling needs to be visible
+ * before doing these things.
*/
smp_mb__after_atomic();
+ sched_ttwu_pending();
schedule_preempt_disabled();
}
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 956b8ca24893..2f8636199b83 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -670,6 +670,8 @@ extern int migrate_swap(struct task_struct *, struct task_struct *);
#ifdef CONFIG_SMP
+extern void sched_ttwu_pending(void);
+
#define rcu_dereference_check_sched_domain(p) \
rcu_dereference_check((p), \
lockdep_is_held(&sched_domains_mutex))
@@ -787,6 +789,10 @@ static inline unsigned int group_first_cpu(struct sched_group *group)
extern int group_balance_cpu(struct sched_group *sg);
+#else
+
+static inline void sched_ttwu_pending(void) { }
+
#endif /* CONFIG_SMP */
#include "stats.h"