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Subject[PATCH v3 2/4] sched/core: Avoid double calling update_rq_clock() in __balance_push_cpu_stop()
Date
The WARN_DOUBLE_CLOCK warning is triggered during cpu offline.
------------[ cut here ]------------
rq->clock_update_flags & RQCF_UPDATED
WARNING: CPU: 17 PID: 138 at kernel/sched/core.c:741
update_rq_clock+0xaf/0x180
Call Trace:
<TASK>
__balance_push_cpu_stop+0x146/0x180
? migration_cpu_stop+0x2a0/0x2a0
cpu_stopper_thread+0xa3/0x140
smpboot_thread_fn+0x14f/0x210
? sort_range+0x20/0x20
kthread+0xe6/0x110
? kthread_complete_and_exit+0x20/0x20
ret_from_fork+0x1f/0x30

To avoid this warning, we remove update_rq_clock() from
the __migrate_task() function. And in order to avoid
missing rq clock update, add update_rq_clock() call before
migration_cpu_stop() calls __migrate_task().

Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
---
kernel/sched/core.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 944c3ae39861..2bcf6a8e71fc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2398,7 +2398,6 @@ static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
if (!is_cpu_allowed(p, dest_cpu))
return rq;

- update_rq_clock(rq);
rq = move_queued_task(rq, rf, p, dest_cpu);

return rq;
@@ -2456,10 +2455,12 @@ static int migration_cpu_stop(void *data)
goto out;
}

- if (task_on_rq_queued(p))
+ if (task_on_rq_queued(p)) {
+ update_rq_clock(rq);
rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
- else
+ } else {
p->wake_cpu = arg->dest_cpu;
+ }

/*
* XXX __migrate_task() can fail, at which point we might end
--
2.37.0
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