Changes from v2
- Run spellchecker over the text and fix typos
- Add acked-by Daniel
Changes from v1
- Enhance commit msg
- Prevent WARN in cpumask_test_cpu() in cpudl_find() when best_cpu == -1
-----8<-----
>From 7735382d07ae6a61d740ae39ba2ecf169d43b8a2 Mon Sep 17 00:00:00 2001
From: Byungchul Park <[email protected]>
Date: Wed, 22 Mar 2017 14:25:56 +0900
Subject: [RESEND PATCH v3 1/2] sched/deadline: Add cpudl_maximum_dl() for clean-up
Current code uses cpudl_maximum() to get the root node's cpu, while it
directly accesses the root node like 'cp->elements[0].dl' to get the
root node's dl. It would be more readable to add a function for the dl,
as well. Added it.
Signed-off-by: Byungchul Park <[email protected]>
Acked-by: Steven Rostedt (VMware) <[email protected]>
Acked-by: Daniel Bristot de Oliveira <[email protected]>
---
kernel/sched/cpudeadline.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 8d9562d..9f02035 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -108,11 +108,16 @@ static void cpudl_heapify(struct cpudl *cp, int idx)
cpudl_heapify_down(cp, idx);
}
-static inline int cpudl_maximum(struct cpudl *cp)
+static inline int cpudl_maximum_cpu(struct cpudl *cp)
{
return cp->elements[0].cpu;
}
+static inline u64 cpudl_maximum_dl(struct cpudl *cp)
+{
+ return cp->elements[0].dl;
+}
+
/*
* cpudl_find - find the best (later-dl) CPU in the system
* @cp: the cpudl max-heap context
@@ -130,11 +135,11 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
return 1;
} else {
- int best_cpu = cpudl_maximum(cp);
+ int best_cpu = cpudl_maximum_cpu(cp);
WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
- dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
+ dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
if (later_mask)
cpumask_set_cpu(best_cpu, later_mask);
--
1.9.1
Currently, migrating tasks to cpu0 unconditionally happens when the
heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0).
We have to distinguish between the empty case and cpu0 to avoid the
unnecessary migrations. Therefore, it has to return an invalid value
e.i. -1 in that case.
Signed-off-by: Byungchul Park <[email protected]>
Acked-by: Steven Rostedt (VMware) <[email protected]>
Acked-by: Daniel Bristot de Oliveira <[email protected]>
---
kernel/sched/cpudeadline.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 9f02035..bcf903f 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
int best_cpu = cpudl_maximum_cpu(cp);
WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
+ /*
+ * The heap tree is empty for now, just return.
+ */
+ if (best_cpu == -1)
+ return 0;
+
if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
if (later_mask)
@@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp)
return -ENOMEM;
}
- for_each_possible_cpu(i)
+ for_each_possible_cpu(i) {
+ cp->elements[i].cpu = -1;
cp->elements[i].idx = IDX_INVALID;
+ }
return 0;
}
--
1.9.1
Sorry for the huge delay on this, but I'll have to postpone further.
Still busy with meltdown/spectre stuff.
On 1/11/2018 6:07 PM, Peter Zijlstra wrote:
>
>
> Sorry for the huge delay on this, but I'll have to postpone further.
> Still busy with meltdown/spectre stuff.
Do you have time to see these patches and another set, now?
--
Thanks,
Byungchul
On 1/11/2018 6:07 PM, Peter Zijlstra wrote:
>
>
> Sorry for the huge delay on this, but I'll have to postpone further.
> Still busy with meltdown/spectre stuff.
Do you have time to see the patch, now that it seems to be managed
to solve those security issues?
--
Thanks,
Byungchul
On 1/11/2018 6:07 PM, Peter Zijlstra wrote:
>
>
> Sorry for the huge delay on this, but I'll have to postpone further.
> Still busy with meltdown/spectre stuff.
Could you review the patch?
--
Thanks,
Byungchul
On 3/13/2018 2:52 PM, Byungchul Park wrote:
> On 1/11/2018 6:07 PM, Peter Zijlstra wrote:
>>
>>
>> Sorry for the huge delay on this, but I'll have to postpone further.
>> Still busy with meltdown/spectre stuff.
>
> Could you review the patch?
Hello,
Could you see the patch now?
--
Thanks,
Byungchul
On Thu, Jan 11, 2018 at 10:07:16AM +0100, Peter Zijlstra wrote:
>
>
> Sorry for the huge delay on this, but I'll have to postpone further.
> Still busy with meltdown/spectre stuff.
Please consider this. Even though it's not a big bug, anyway leading
mis-behavior in certain situaions.
On 2018-05-09 15:33, Byungchul Park wrote:
> On Thu, Jan 11, 2018 at 10:07:16AM +0100, Peter Zijlstra wrote:
>>
>>
>> Sorry for the huge delay on this, but I'll have to postpone further.
>> Still busy with meltdown/spectre stuff.
>
> Please consider this. Even though it's not a big bug, anyway leading
> mis-behavior in certain situaions.
Could you see this patches, it's been too long since the start tho?
--
Thanks,
Byungchul
On 2018-05-25 14:13, Byungchul Park wrote:
>
>
> On 2018-05-09 15:33, Byungchul Park wrote:
>> On Thu, Jan 11, 2018 at 10:07:16AM +0100, Peter Zijlstra wrote:
>>>
>>>
>>> Sorry for the huge delay on this, but I'll have to postpone further.
>>> Still busy with meltdown/spectre stuff.
>>
>> Please consider this. Even though it's not a big bug, anyway leading
>> mis-behavior in certain situaions.
>
> Could you see this patches, it's been too long since the start tho?
Please, any opinion.
--
Thanks,
Byungchul
On Fri, Jun 01, 2018 at 12:07:48PM +0900, Byungchul Park wrote:
>
>
> On 2018-05-25 14:13, Byungchul Park wrote:
> >
> >
> > On 2018-05-09 15:33, Byungchul Park wrote:
> > > On Thu, Jan 11, 2018 at 10:07:16AM +0100, Peter Zijlstra wrote:
> > > >
> > > >
> > > > Sorry for the huge delay on this, but I'll have to postpone further.
> > > > Still busy with meltdown/spectre stuff.
> > >
> > > Please consider this. Even though it's not a big bug, anyway leading
> > > mis-behavior in certain situaions.
> >
> > Could you see this patches, it's been too long since the start tho?
>
> Please, any opinion.
Just my opinion: this patch [1] is just a cosmetic change. I would argue that
there's no readability improvement by wrapping up elements[0].dl. Infact I
even feel that the elements[0].cpu should directly be accessed since both
.cpu and .dl for the 0th element are directly accessed only from one place
(cpudl_find) and only one time, and explicitly accessing index 0 makes it
more clear that this is the root of the max-heap.
IOW I don't see any benefit in hiding it behind a wrapper which hides the
fact that we're accessing the root of the max heap, but I don't terribly hate
this patch and I'm Ok if maintainers and other reviewers think its worth it.
thanks,
- Joel
[1] https://patchwork.kernel.org/patch/10149099/
On Mon, Jan 08, 2018 at 03:14:41PM +0900, byungchul park wrote:
> Currently, migrating tasks to cpu0 unconditionally happens when the
> heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0).
> We have to distinguish between the empty case and cpu0 to avoid the
> unnecessary migrations. Therefore, it has to return an invalid value
> e.i. -1 in that case.
>
> Signed-off-by: Byungchul Park <[email protected]>
> Acked-by: Steven Rostedt (VMware) <[email protected]>
> Acked-by: Daniel Bristot de Oliveira <[email protected]>
> ---
> kernel/sched/cpudeadline.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> index 9f02035..bcf903f 100644
> --- a/kernel/sched/cpudeadline.c
> +++ b/kernel/sched/cpudeadline.c
> @@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
> int best_cpu = cpudl_maximum_cpu(cp);
> WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
>
> + /*
> + * The heap tree is empty for now, just return.
> + */
> + if (best_cpu == -1)
> + return 0;
> +
> if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
> dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
> if (later_mask)
> @@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp)
> return -ENOMEM;
> }
>
> - for_each_possible_cpu(i)
> + for_each_possible_cpu(i) {
> + cp->elements[i].cpu = -1;
> cp->elements[i].idx = IDX_INVALID;
Shouldn't you also set cp->elements[cpu].cpu to -1 in cpudl_clear (when you
set cp->elements[cpu].cpu to IDX_INVALID there)?
thanks,
- Joel
On Thu, May 31, 2018 at 11:12:55PM -0700, Joel Fernandes wrote:
> On Mon, Jan 08, 2018 at 03:14:41PM +0900, byungchul park wrote:
> > Currently, migrating tasks to cpu0 unconditionally happens when the
> > heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0).
> > We have to distinguish between the empty case and cpu0 to avoid the
> > unnecessary migrations. Therefore, it has to return an invalid value
> > e.i. -1 in that case.
> >
> > Signed-off-by: Byungchul Park <[email protected]>
> > Acked-by: Steven Rostedt (VMware) <[email protected]>
> > Acked-by: Daniel Bristot de Oliveira <[email protected]>
> > ---
> > kernel/sched/cpudeadline.c | 10 +++++++++-
> > 1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> > index 9f02035..bcf903f 100644
> > --- a/kernel/sched/cpudeadline.c
> > +++ b/kernel/sched/cpudeadline.c
> > @@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
> > int best_cpu = cpudl_maximum_cpu(cp);
> > WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
> >
> > + /*
> > + * The heap tree is empty for now, just return.
> > + */
> > + if (best_cpu == -1)
> > + return 0;
> > +
> > if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
> > dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
> > if (later_mask)
> > @@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp)
> > return -ENOMEM;
> > }
> >
> > - for_each_possible_cpu(i)
> > + for_each_possible_cpu(i) {
> > + cp->elements[i].cpu = -1;
> > cp->elements[i].idx = IDX_INVALID;
>
> Shouldn't you also set cp->elements[cpu].cpu to -1 in cpudl_clear (when you
> set cp->elements[cpu].cpu to IDX_INVALID there)?
I messed up my words, I meant : "when setting cp->elements[cpu].idx to
IDX_INVALID there". Which means I need to call it a day :-)
- Joel
On 2018-06-01 15:02, Joel Fernandes wrote:
> On Fri, Jun 01, 2018 at 12:07:48PM +0900, Byungchul Park wrote:
>>
>>
>> On 2018-05-25 14:13, Byungchul Park wrote:
>>>
>>>
>>> On 2018-05-09 15:33, Byungchul Park wrote:
>>>> On Thu, Jan 11, 2018 at 10:07:16AM +0100, Peter Zijlstra wrote:
>>>>>
>>>>>
>>>>> Sorry for the huge delay on this, but I'll have to postpone further.
>>>>> Still busy with meltdown/spectre stuff.
>>>>
>>>> Please consider this. Even though it's not a big bug, anyway leading
>>>> mis-behavior in certain situaions.
>>>
>>> Could you see this patches, it's been too long since the start tho?
>>
>> Please, any opinion.
>
> Just my opinion: this patch [1] is just a cosmetic change. I would argue that
> there's no readability improvement by wrapping up elements[0].dl. Infact I
> even feel that the elements[0].cpu should directly be accessed since both
> .cpu and .dl for the 0th element are directly accessed only from one place
> (cpudl_find) and only one time, and explicitly accessing index 0 makes it
> more clear that this is the root of the max-heap.
>
> IOW I don't see any benefit in hiding it behind a wrapper which hides the
> fact that we're accessing the root of the max heap, but I don't terribly hate
> this patch and I'm Ok if maintainers and other reviewers think its worth it.
Hi Joel,
Talking about the *1st patch*, no matter whether denied or not, even
though I think it looks weird to abstract only p->elements[0].cpu with
a function, but not cp->elements[0].dl.
> thanks,
>
> - Joel
>
> [1] https://patchwork.kernel.org/patch/10149099/
>
>
--
Thanks,
Byungchul
On 2018-06-01 15:18, Joel Fernandes wrote:
> On Thu, May 31, 2018 at 11:12:55PM -0700, Joel Fernandes wrote:
>> On Mon, Jan 08, 2018 at 03:14:41PM +0900, byungchul park wrote:
>>> Currently, migrating tasks to cpu0 unconditionally happens when the
>>> heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0).
>>> We have to distinguish between the empty case and cpu0 to avoid the
>>> unnecessary migrations. Therefore, it has to return an invalid value
>>> e.i. -1 in that case.
>>>
>>> Signed-off-by: Byungchul Park <[email protected]>
>>> Acked-by: Steven Rostedt (VMware) <[email protected]>
>>> Acked-by: Daniel Bristot de Oliveira <[email protected]>
>>> ---
>>> kernel/sched/cpudeadline.c | 10 +++++++++-
>>> 1 file changed, 9 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
>>> index 9f02035..bcf903f 100644
>>> --- a/kernel/sched/cpudeadline.c
>>> +++ b/kernel/sched/cpudeadline.c
>>> @@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
>>> int best_cpu = cpudl_maximum_cpu(cp);
>>> WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
>>>
>>> + /*
>>> + * The heap tree is empty for now, just return.
>>> + */
>>> + if (best_cpu == -1)
>>> + return 0;
>>> +
>>> if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
>>> dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
>>> if (later_mask)
>>> @@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp)
>>> return -ENOMEM;
>>> }
>>>
>>> - for_each_possible_cpu(i)
>>> + for_each_possible_cpu(i) {
>>> + cp->elements[i].cpu = -1;
>>> cp->elements[i].idx = IDX_INVALID;
>>
>> Shouldn't you also set cp->elements[cpu].cpu to -1 in cpudl_clear (when you
>> set cp->elements[cpu].cpu to IDX_INVALID there)?
>
> I messed up my words, I meant : "when setting cp->elements[cpu].idx to
> IDX_INVALID there". Which means I need to call it a day :-)
Ah.. I agree with you. It might be a problem when removing the last
element.. Then I think the following change should also be applied
additionally. Right?
---
diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 8d9562d..44d4c88 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -172,12 +172,14 @@ void cpudl_clear(struct cpudl *cp, int cpu)
} else {
new_cpu = cp->elements[cp->size - 1].cpu;
cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
- cp->elements[old_idx].cpu = new_cpu;
+ cp->elements[old_idx].cpu = (new_cpu == cpu) ? -1 : new_cpu;
cp->size--;
- cp->elements[new_cpu].idx = old_idx;
cp->elements[cpu].idx = IDX_INVALID;
- cpudl_heapify(cp, old_idx);
+ if (new_cpu != cpu) {
+ cp->elements[new_cpu].idx = old_idx;
+ cpudl_heapify(cp, old_idx);
+ }
cpumask_set_cpu(cpu, cp->free_cpus);
}
raw_spin_unlock_irqrestore(&cp->lock, flags);
--
Thanks,
Byungchul
On Fri, Jun 01, 2018 at 04:10:56PM +0900, Byungchul Park wrote:
> > On Thu, May 31, 2018 at 11:12:55PM -0700, Joel Fernandes wrote:
> > > On Mon, Jan 08, 2018 at 03:14:41PM +0900, byungchul park wrote:
> > > > Currently, migrating tasks to cpu0 unconditionally happens when the
> > > > heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0).
> > > > We have to distinguish between the empty case and cpu0 to avoid the
> > > > unnecessary migrations. Therefore, it has to return an invalid value
> > > > e.i. -1 in that case.
> > > >
> > > > Signed-off-by: Byungchul Park <[email protected]>
> > > > Acked-by: Steven Rostedt (VMware) <[email protected]>
> > > > Acked-by: Daniel Bristot de Oliveira <[email protected]>
> > > > ---
> > > > kernel/sched/cpudeadline.c | 10 +++++++++-
> > > > 1 file changed, 9 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> > > > index 9f02035..bcf903f 100644
> > > > --- a/kernel/sched/cpudeadline.c
> > > > +++ b/kernel/sched/cpudeadline.c
> > > > @@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
> > > > int best_cpu = cpudl_maximum_cpu(cp);
> > > > WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
> > > > + /*
> > > > + * The heap tree is empty for now, just return.
> > > > + */
> > > > + if (best_cpu == -1)
> > > > + return 0;
> > > > +
> > > > if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
> > > > dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
> > > > if (later_mask)
> > > > @@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp)
> > > > return -ENOMEM;
> > > > }
> > > > - for_each_possible_cpu(i)
> > > > + for_each_possible_cpu(i) {
> > > > + cp->elements[i].cpu = -1;
> > > > cp->elements[i].idx = IDX_INVALID;
> > >
> > > Shouldn't you also set cp->elements[cpu].cpu to -1 in cpudl_clear (when you
> > > set cp->elements[cpu].cpu to IDX_INVALID there)?
> >
> > I messed up my words, I meant : "when setting cp->elements[cpu].idx to
> > IDX_INVALID there". Which means I need to call it a day :-)
>
> Ah.. I agree with you. It might be a problem when removing the last
> element.. Then I think the following change should also be applied
> additionally. Right?
Yes.
> ---
> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> index 8d9562d..44d4c88 100644
> --- a/kernel/sched/cpudeadline.c
> +++ b/kernel/sched/cpudeadline.c
> @@ -172,12 +172,14 @@ void cpudl_clear(struct cpudl *cp, int cpu)
> } else {
> new_cpu = cp->elements[cp->size - 1].cpu;
> cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
> - cp->elements[old_idx].cpu = new_cpu;
> + cp->elements[old_idx].cpu = (new_cpu == cpu) ? -1 : new_cpu;
> cp->size--;
> - cp->elements[new_cpu].idx = old_idx;
> cp->elements[cpu].idx = IDX_INVALID;
> - cpudl_heapify(cp, old_idx);
>
> + if (new_cpu != cpu) {
> + cp->elements[new_cpu].idx = old_idx;
> + cpudl_heapify(cp, old_idx);
> + }
> cpumask_set_cpu(cpu, cp->free_cpus);
This looks a bit confusing. How about the following? (untested)
thanks,
- Joel
---8<-----------------------
diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 50316455ea66..741a97e58c05 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -129,6 +129,10 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
} else {
int best_cpu = cpudl_maximum(cp);
+ /* The max-heap is empty, just return. */
+ if (best_cpu == -1)
+ return 0;
+
WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
@@ -167,6 +171,12 @@ void cpudl_clear(struct cpudl *cp, int cpu)
* This could happen if a rq_offline_dl is
* called for a CPU without -dl tasks running.
*/
+ } else if (cp->size == 1) {
+ /* Only one element in max-heap, clear it */
+ cp->elements[0].cpu = -1;
+ cp->elements[cpu].idx = IDX_INVALID;
+ cp->size--;
+ cpumask_set_cpu(cpu, cp->free_cpus);
} else {
new_cpu = cp->elements[cp->size - 1].cpu;
cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
@@ -262,6 +272,9 @@ int cpudl_init(struct cpudl *cp)
for_each_possible_cpu(i)
cp->elements[i].idx = IDX_INVALID;
+ /* Mark heap as initially empty */
+ cp->elements[0].cpu = -1;
+
return 0;
}
On Sat, Jun 2, 2018 at 12:52 AM, Joel Fernandes <[email protected]> wrote:
> On Fri, Jun 01, 2018 at 04:10:56PM +0900, Byungchul Park wrote:
>> > On Thu, May 31, 2018 at 11:12:55PM -0700, Joel Fernandes wrote:
>> > > On Mon, Jan 08, 2018 at 03:14:41PM +0900, byungchul park wrote:
>> > > > Currently, migrating tasks to cpu0 unconditionally happens when the
>> > > > heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0).
>> > > > We have to distinguish between the empty case and cpu0 to avoid the
>> > > > unnecessary migrations. Therefore, it has to return an invalid value
>> > > > e.i. -1 in that case.
>> > > >
>> > > > Signed-off-by: Byungchul Park <[email protected]>
>> > > > Acked-by: Steven Rostedt (VMware) <[email protected]>
>> > > > Acked-by: Daniel Bristot de Oliveira <[email protected]>
>> > > > ---
>> > > > kernel/sched/cpudeadline.c | 10 +++++++++-
>> > > > 1 file changed, 9 insertions(+), 1 deletion(-)
>> > > >
>> > > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
>> > > > index 9f02035..bcf903f 100644
>> > > > --- a/kernel/sched/cpudeadline.c
>> > > > +++ b/kernel/sched/cpudeadline.c
>> > > > @@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
>> > > > int best_cpu = cpudl_maximum_cpu(cp);
>> > > > WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
>> > > > + /*
>> > > > + * The heap tree is empty for now, just return.
>> > > > + */
>> > > > + if (best_cpu == -1)
>> > > > + return 0;
>> > > > +
>> > > > if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
>> > > > dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) {
>> > > > if (later_mask)
>> > > > @@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp)
>> > > > return -ENOMEM;
>> > > > }
>> > > > - for_each_possible_cpu(i)
>> > > > + for_each_possible_cpu(i) {
>> > > > + cp->elements[i].cpu = -1;
>> > > > cp->elements[i].idx = IDX_INVALID;
>> > >
>> > > Shouldn't you also set cp->elements[cpu].cpu to -1 in cpudl_clear (when you
>> > > set cp->elements[cpu].cpu to IDX_INVALID there)?
>> >
>> > I messed up my words, I meant : "when setting cp->elements[cpu].idx to
>> > IDX_INVALID there". Which means I need to call it a day :-)
>>
>> Ah.. I agree with you. It might be a problem when removing the last
>> element.. Then I think the following change should also be applied
>> additionally. Right?
>
> Yes.
>
>> ---
>> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
>> index 8d9562d..44d4c88 100644
>> --- a/kernel/sched/cpudeadline.c
>> +++ b/kernel/sched/cpudeadline.c
>> @@ -172,12 +172,14 @@ void cpudl_clear(struct cpudl *cp, int cpu)
>> } else {
>> new_cpu = cp->elements[cp->size - 1].cpu;
>> cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
>> - cp->elements[old_idx].cpu = new_cpu;
>> + cp->elements[old_idx].cpu = (new_cpu == cpu) ? -1 : new_cpu;
>> cp->size--;
>> - cp->elements[new_cpu].idx = old_idx;
>> cp->elements[cpu].idx = IDX_INVALID;
>> - cpudl_heapify(cp, old_idx);
>>
>> + if (new_cpu != cpu) {
>> + cp->elements[new_cpu].idx = old_idx;
>> + cpudl_heapify(cp, old_idx);
>> + }
>> cpumask_set_cpu(cpu, cp->free_cpus);
>
> This looks a bit confusing. How about the following? (untested)
Hello,
Whatever. Your code also looks good to me.
I just wanna follow the maintainers' decision. ;)
> thanks,
>
> - Joel
>
> ---8<-----------------------
>
> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> index 50316455ea66..741a97e58c05 100644
> --- a/kernel/sched/cpudeadline.c
> +++ b/kernel/sched/cpudeadline.c
> @@ -129,6 +129,10 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
> } else {
> int best_cpu = cpudl_maximum(cp);
>
> + /* The max-heap is empty, just return. */
> + if (best_cpu == -1)
> + return 0;
> +
> WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
>
> if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) &&
> @@ -167,6 +171,12 @@ void cpudl_clear(struct cpudl *cp, int cpu)
> * This could happen if a rq_offline_dl is
> * called for a CPU without -dl tasks running.
> */
> + } else if (cp->size == 1) {
> + /* Only one element in max-heap, clear it */
> + cp->elements[0].cpu = -1;
> + cp->elements[cpu].idx = IDX_INVALID;
> + cp->size--;
> + cpumask_set_cpu(cpu, cp->free_cpus);
> } else {
> new_cpu = cp->elements[cp->size - 1].cpu;
> cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
> @@ -262,6 +272,9 @@ int cpudl_init(struct cpudl *cp)
> for_each_possible_cpu(i)
> cp->elements[i].idx = IDX_INVALID;
>
> + /* Mark heap as initially empty */
> + cp->elements[0].cpu = -1;
> +
> return 0;
> }
>
--
Thanks,
Byungchul