v2: Changed comment
When p is current and it's not of dl class, then there are no other
dl taks in the rq. If we had had pushable tasks in some other rq,
they would have been pushed earlier. So, skip "p == rq->curr" case.
[This is confirmed by Juri Lelli and LKML was CC'ed, but
unfotunately I can't find direct link on lkml.org]
Signed-off-by: Kirill Tkhai <[email protected]>
CC: Juri Lelli <[email protected]>
CC: Peter Zijlstra <[email protected]>
CC: Ingo Molnar <[email protected]>
---
kernel/sched/deadline.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 0de2482..dd19d6d 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1559,7 +1559,7 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
if (unlikely(p->dl.dl_throttled))
return;
- if (p->on_rq || rq->curr != p) {
+ if (p->on_rq && rq->curr != p) {
#ifdef CONFIG_SMP
if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
/* Only reschedule if pushing failed */
On 01/28/2014 08:26 AM, Kirill Tkhai wrote:
> v2: Changed comment
>
> When p is current and it's not of dl class, then there are no other
> dl taks in the rq. If we had had pushable tasks in some other rq,
^ tasks
> they would have been pushed earlier. So, skip "p == rq->curr" case.
>
> [This is confirmed by Juri Lelli and LKML was CC'ed, but
> unfotunately I can't find direct link on lkml.org]
>
This was the story:
> On 01/08/2014 10:00 AM, Juri Lelli wrote:
>> On 12/18/2013 04:00 PM, Kirill Tkhai wrote:
>>> 17.12.2013, 16:48, "Peter Zijlstra" <[email protected]>:
>>> From: Dario Faggioli <[email protected]>
>>>
>>> Introduces the data structures, constants and symbols needed for
>>> SCHED_DEADLINE implementation.
>>
>> [snipped]
>>
>>> +static void switched_to_dl(struct rq *rq, struct task_struct *p)
>>> +{
>>> + /*
>>> + * If p is throttled, don't consider the possibility
>>> + * of preempting rq->curr, the check will be done right
>>> + * after its runtime will get replenished.
>>> + */
>>> + if (unlikely(p->dl.dl_throttled))
>>> + return;
>>> +
>>> + if (!p->on_rq || rq->curr != p) {
>>> + if (task_has_dl_policy(rq->curr))
>>> + check_preempt_curr_dl(rq, p, 0);
>>> + else
>>> + resched_task(rq->curr);
>>> + }
>>> +}
>>
>> The second if() looks a little strange. Why is "!p->on_rq ||" here? RT class
>> has another logic.
>>
>
> You are right, good catch! :)
>
> This has to be changed in
>
> if (p->on_rq && rq->curr != p)
>
> as in RT.
>
> Thanks,
>
> - Juri
> Signed-off-by: Kirill Tkhai <[email protected]>
> CC: Juri Lelli <[email protected]>
> CC: Peter Zijlstra <[email protected]>
> CC: Ingo Molnar <[email protected]>
> ---
> kernel/sched/deadline.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 0de2482..dd19d6d 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1559,7 +1559,7 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
> if (unlikely(p->dl.dl_throttled))
> return;
>
> - if (p->on_rq || rq->curr != p) {
> + if (p->on_rq && rq->curr != p) {
> #ifdef CONFIG_SMP
> if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
> /* Only reschedule if pushing failed */
>
So the patch looks good. Not sure about the changelog, though :).
Thanks,
- Juri
Commit-ID: 390f3258cb2d031f1c17aa32e771ebd336e89073
Gitweb: http://git.kernel.org/tip/390f3258cb2d031f1c17aa32e771ebd336e89073
Author: Kirill Tkhai <[email protected]>
AuthorDate: Tue, 28 Jan 2014 11:26:14 +0400
Committer: Ingo Molnar <[email protected]>
CommitDate: Sun, 9 Feb 2014 13:31:48 +0100
sched/deadline: Skip in switched_to_dl() if task is current
When p is current and it's not of dl class, then there are no other
dl taks in the rq. If we had had pushable tasks in some other rq,
they would have been pushed earlier. So, skip "p == rq->curr" case.
Signed-off-by: Kirill Tkhai <[email protected]>
Acked-by: Juri Lelli <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/20140128072421.32315.25300.stgit@tkhai
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/sched/deadline.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 0dd5e09..b5700bc 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1560,7 +1560,7 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
if (unlikely(p->dl.dl_throttled))
return;
- if (p->on_rq || rq->curr != p) {
+ if (p->on_rq && rq->curr != p) {
#ifdef CONFIG_SMP
if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
/* Only reschedule if pushing failed */