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Message-ID: <53BBDAFE.1070309@huawei.com>
Date: Tue, 8 Jul 2014 19:50:22 +0800
From: "xiaofeng.yan" <xiaofeng.yan@...wei.com>
To: Peter Zijlstra <peterz@...radead.org>
CC: <mingo@...hat.com>, <juri.lelli@...il.com>,
<linux-kernel@...r.kernel.org>, <xiaofeng.yan2012@...il.com>
Subject: Re: [PATCH] sched/deadline: overrun could happen in start_hrtick_dl
On 2014/7/8 19:23, xiaofeng.yan wrote:
> On 2014/7/8 17:33, Peter Zijlstra wrote:
>> On Tue, Jul 08, 2014 at 08:53:27AM +0000, xiaofeng.yan wrote:
>>> static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
>>> {
>>> - s64 delta = p->dl.dl_runtime - p->dl.runtime;
>>> -
>>> - if (delta > 10000)
>>> - hrtick_start(rq, p->dl.runtime);
>>> + delta = max_t(s64, 10000LL, delta);
>>> + hrtick_start(rq, delta);
>>> }
>> no, no, no. I said to unify the test.
>
> I understand your idea after reading the next patch. This is good
> solution.
> I will test it with your patch.
>
I have tested this solution, It can work very well with deadline
schedule class.
kernel/sched/core.c | 9 ++++++++-
kernel/sched/deadline.c | 5 +----
kernel/sched/fair.c | 8 --------
3 files changed, 9 insertions(+), 13 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3bdf01b..cc9a058 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -442,8 +442,15 @@ static void __hrtick_start(void *arg)
void hrtick_start(struct rq *rq, u64 delay)
{
struct hrtimer *timer = &rq->hrtick_timer;
- ktime_t time = ktime_add_ns(timer->base->get_time(), delay);
+ ktime_t time;
+
+ /*
+ * Don't schedule slices shorter than 10000ns, that just
+ * doesn't make sense and can cause timer DoS.
+ */
+ s64 delta = max_t(s64, delay, 10000LL);
+ time = ktime_add_ns(timer->base->get_time(), delta);
hrtimer_set_expires(timer, time);
if (rq == this_rq()) {
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index fc4f98b1..9135771 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -997,10 +997,7 @@ static void check_preempt_curr_dl(struct rq *rq,
struct task_struct *p,
#ifdef CONFIG_SCHED_HRTICK
static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
{
- s64 delta = p->dl.dl_runtime - p->dl.runtime;
-
- if (delta > 10000)
- hrtick_start(rq, p->dl.runtime);
+ hrtick_start(rq, p->dl.runtime);
}
#endif
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fea7d33..e5cfd57 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3857,14 +3857,6 @@ static void hrtick_start_fair(struct rq *rq,
struct task_struct *p)
resched_task(p);
return;
}
-
- /*
- * Don't schedule slices shorter than 10000ns, that just
- * doesn't make sense. Rely on vruntime for fairness.
- */
- if (rq->curr != p)
- delta = max_t(s64, 10000LL, delta);
-
hrtick_start(rq, delta);
}
}
--
>> ---
>> kernel/sched/core.c | 9 ++++++++-
>> kernel/sched/deadline.c | 3 +--
>> kernel/sched/fair.c | 7 -------
>> 3 files changed, 9 insertions(+), 10 deletions(-)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index e1a2f31bb0cb..c7b8a6fbac66 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -444,7 +444,14 @@ static void __hrtick_start(void *arg)
>> void hrtick_start(struct rq *rq, u64 delay)
>> {
>> struct hrtimer *timer = &rq->hrtick_timer;
>> - ktime_t time = ktime_add_ns(timer->base->get_time(), delay);
>> + ktime_t time;
>> +
>> + /*
>> + * Don't schedule slices shorter than 10000ns, that just
>> + * doesn't make sense and can cause timer DoS.
>> + */
>> + delta = max_t(s64, delta, 10000LL);
>
> transfer the argument delta to delay
>
>> + time = ktime_add_ns(timer->base->get_time(), delay);
>> hrtimer_set_expires(timer, time);
>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>> index fc4f98b1258f..e1e24eea8061 100644
>> --- a/kernel/sched/deadline.c
>> +++ b/kernel/sched/deadline.c
>> @@ -999,8 +999,7 @@ static void start_hrtick_dl(struct rq *rq, struct
>> task_struct *p)
>> {
>> s64 delta = p->dl.dl_runtime - p->dl.runtime;
>> - if (delta > 10000)
>> - hrtick_start(rq, p->dl.runtime);
>> + hrtick_start(rq, p->dl.runtime);
>> }
>> #endif
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 923fe32db6b3..713c58d2a7b0 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -3901,13 +3901,6 @@ static void hrtick_start_fair(struct rq *rq,
>> struct task_struct *p)
>> return;
>> }
>> - /*
>> - * Don't schedule slices shorter than 10000ns, that just
>> - * doesn't make sense. Rely on vruntime for fairness.
>> - */
>> - if (rq->curr != p)
>> - delta = max_t(s64, 10000LL, delta);
>> -
>> hrtick_start(rq, delta);
>> }
>> }
>
>
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