From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] sched_rt: protect rt_rq->rt_time by rt_runtime_lock
Date: Thu, 05 Feb 2009 16:06:43 -0800 [thread overview]
Message-ID: <498B7F13.7040104@ct.jp.nec.com> (raw)
In-Reply-To: <1233878343.4620.44.camel@laptop>
Peter Zijlstra wrote:
> On Thu, 2009-02-05 at 15:38 -0800, Hiroshi Shimamoto wrote:
>> From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
>>
>> Impact: fix possible race condition
>>
>> rt_rq->rt_time should be protected.
>
> Don't think so, all we do is check the value for non-zero outside the
> lock, that should be ok.
>
> If there's still a race, your changelog utterly fails to mention the
> race scenario.
OK. I just noticed rt_time is accessed with rt_runtime_lock held except
this point. Will look at this again.
Thanks,
Hiroshi
>
>> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
>> ---
>> kernel/sched_rt.c | 4 ++--
>> 1 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
>> index 299d012..d7654a3 100644
>> --- a/kernel/sched_rt.c
>> +++ b/kernel/sched_rt.c
>> @@ -496,10 +496,10 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
>> struct rq *rq = rq_of_rt_rq(rt_rq);
>>
>> spin_lock(&rq->lock);
>> + spin_lock(&rt_rq->rt_runtime_lock);
>> if (rt_rq->rt_time) {
>> u64 runtime;
>>
>> - spin_lock(&rt_rq->rt_runtime_lock);
>> if (rt_rq->rt_throttled)
>> balance_runtime(rt_rq);
>> runtime = rt_rq->rt_runtime;
>> @@ -510,9 +510,9 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
>> }
>> if (rt_rq->rt_time || rt_rq->rt_nr_running)
>> idle = 0;
>> - spin_unlock(&rt_rq->rt_runtime_lock);
>> } else if (rt_rq->rt_nr_running)
>> idle = 0;
>> + spin_unlock(&rt_rq->rt_runtime_lock);
>>
>> if (enqueue)
>> sched_rt_rq_enqueue(rt_rq);
>
> --
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next prev parent reply other threads:[~2009-02-06 0:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-05 23:36 [PATCH 1/2] sched_rt: don't start timer when rt bandwidth disabled Hiroshi Shimamoto
2009-02-05 23:38 ` [PATCH 2/2] sched_rt: protect rt_rq->rt_time by rt_runtime_lock Hiroshi Shimamoto
2009-02-05 23:59 ` Peter Zijlstra
2009-02-06 0:06 ` Hiroshi Shimamoto [this message]
2009-02-06 18:50 ` Hiroshi Shimamoto
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