The patch titled
sched: reinitialise rt_rq->rt_throttled in __enable_runtime()
has been added to the -mm tree. Its filename is
sched-reinitialise-rt_rq-rt_throttled-in-__enable_runtime.patch
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------------------------------------------------------
Subject: sched: reinitialise rt_rq->rt_throttled in __enable_runtime()
From: "Zhang, Yanmin" <yanmin_zhang@xxxxxxxxxxxxxxx>
On my tulsa x86-64 machine, kernel 2.6.25-rc5 couldn't boot randomly.
Basically, function __enable_runtime forgets to reset rt_rq->rt_throttled
to 0. When every cpu is up, per-cpu migration_thread is created and it
runs very fast, sometimes to mark the corresponding rt_rq->rt_throttled to
1 very quickly. After all cpus are up, with below calling chain,
sched_init_smp
->arch_init_sched_domains
->build_sched_domains
->...
->cpu_attach_domain
->rq_attach_root
->set_rq_online
->...
->__enable_runtime
__enable_runtime is called against every rt_rq again, so rt_rq->rt_time is
reset to 0, but rt_rq->rt_throttled might be still 1.
Later on function do_sched_rt_period_timer couldn't reset it, and all RT
tasks couldn't be scheduled to run on that cpu. Here is RT task
migration_thread which is woken up when a task is migrated to another cpu.
Signed-off-by: Zhang Yanmin <yanmin_zhang@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/sched_rt.c | 1 +
1 file changed, 1 insertion(+)
diff -puN kernel/sched_rt.c~sched-reinitialise-rt_rq-rt_throttled-in-__enable_runtime kernel/sched_rt.c
--- a/kernel/sched_rt.c~sched-reinitialise-rt_rq-rt_throttled-in-__enable_runtime
+++ a/kernel/sched_rt.c
@@ -350,6 +350,7 @@ static void __enable_runtime(struct rq *
spin_lock(&rt_rq->rt_runtime_lock);
rt_rq->rt_runtime = rt_b->rt_runtime;
rt_rq->rt_time = 0;
+ rt_rq->rt_throttled = 0;
spin_unlock(&rt_rq->rt_runtime_lock);
spin_unlock(&rt_b->rt_runtime_lock);
}
_
Patches currently in -mm which might be from yanmin_zhang@xxxxxxxxxxxxxxx are
sched-reinitialise-rt_rq-rt_throttled-in-__enable_runtime.patch
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