I do not understand the cpu_active() check in select_fallback_rq().
x86 doesn't need it, and the recent commit dd9d3843755d "sched: Fix
cpu_active_mask/cpu_online_mask race" documents the fact that on any
architecture we can ignore !active starting from CPU_ONLINE stage.
But any possible reason why do we need this check in "fallback" must
equally apply to select_task_rq().
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
kernel/sched/core.c | 15 ++++++++-------
1 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5fe9086..a2ef0cf 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1297,6 +1297,11 @@ void kick_process(struct task_struct *p)
}
EXPORT_SYMBOL_GPL(kick_process);
+static inline bool cpu_allowed(int cpu)
+{
+ return cpu_online(cpu) && cpu_active(cpu);
+}
+
/*
* ->cpus_allowed is protected by both rq->lock and p->pi_lock
*/
@@ -1317,9 +1322,7 @@ static int select_fallback_rq(int cpu, struct task_struct
*p)
/* Look for allowed, online CPU in same node. */
for_each_cpu(dest_cpu, nodemask) {
- if (!cpu_online(dest_cpu))
- continue;
- if (!cpu_active(dest_cpu))
+ if (!cpu_allowed(dest_cpu))
continue;
if (cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
return dest_cpu;
@@ -1329,9 +1332,7 @@ static int select_fallback_rq(int cpu, struct task_struct
*p)
for (;;) {
/* Any allowed, online CPU? */
for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) {
- if (!cpu_online(dest_cpu))
- continue;
- if (!cpu_active(dest_cpu))
+ if (!cpu_allowed(dest_cpu))
continue;
goto out;
}
@@ -1390,7 +1391,7 @@ int select_task_rq(struct task_struct *p, int cpu, int
sd_flags, int wake_flags)
* not worry about this generic constraint ]
*/
if (unlikely(!cpumask_test_cpu(cpu, tsk_cpus_allowed(p)) ||
- !cpu_online(cpu)))
+ !cpu_allowed(cpu)))
cpu = select_fallback_rq(task_cpu(p), p);
return cpu;
--
1.5.5.1
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