2014-02-17 14:12:01

by Boris Ostrovsky

Subject: [PATCH] sched/deadline: Test for CPU's presence explicitly

A hot-removed CPU may have ID that is numerically larger than the number of
existing CPUs in the system (e.g. we can unplug CPU 4 from a system that
has CPUs 0, 1 and 4).

Thus the WARN_ONs should check whether the CPU in question is currently
present, not whether its ID value is less than num_present_cpus().

Reported-by: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: Boris Ostrovsky <[email protected]>
---
kernel/sched/cpudeadline.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 045fc74..5b8838b 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -70,7 +70,7 @@ static void cpudl_heapify(struct cpudl *cp, int idx)

static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl)
{
- WARN_ON(idx > num_present_cpus() || idx == IDX_INVALID);
+ WARN_ON(!cpu_present(idx) || idx == IDX_INVALID);

if (dl_time_before(new_dl, cp->elements[idx].dl)) {
cp->elements[idx].dl = new_dl;
@@ -117,7 +117,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
}

out:
- WARN_ON(best_cpu > num_present_cpus() && best_cpu != -1);
+ WARN_ON(!cpu_present(best_cpu) && best_cpu != -1);

return best_cpu;
}
@@ -137,7 +137,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
int old_idx, new_cpu;
unsigned long flags;

- WARN_ON(cpu > num_present_cpus());
+ WARN_ON(!cpu_present(cpu));

raw_spin_lock_irqsave(&cp->lock, flags);
old_idx = cp->cpu_to_idx[cpu];
--
1.8.1.4

2014-02-17 14:50:36

by Peter Zijlstra

Subject: Re: [PATCH] sched/deadline: Test for CPU's presence explicitly

On Mon, Feb 17, 2014 at 09:12:33AM -0500, Boris Ostrovsky wrote:
> A hot-removed CPU may have ID that is numerically larger than the number of
> existing CPUs in the system (e.g. we can unplug CPU 4 from a system that
> has CPUs 0, 1 and 4).
>
> Thus the WARN_ONs should check whether the CPU in question is currently
> present, not whether its ID value is less than num_present_cpus().
>
> Reported-by: Konrad Rzeszutek Wilk <[email protected]>
> Signed-off-by: Boris Ostrovsky <[email protected]>

Thanks!, please also always CC the author of the code in question.

> ---
> kernel/sched/cpudeadline.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> index 045fc74..5b8838b 100644
> --- a/kernel/sched/cpudeadline.c
> +++ b/kernel/sched/cpudeadline.c
> @@ -70,7 +70,7 @@ static void cpudl_heapify(struct cpudl *cp, int idx)
>
> static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl)
> {
> - WARN_ON(idx > num_present_cpus() || idx == IDX_INVALID);
> + WARN_ON(!cpu_present(idx) || idx == IDX_INVALID);
>
> if (dl_time_before(new_dl, cp->elements[idx].dl)) {
> cp->elements[idx].dl = new_dl;
> @@ -117,7 +117,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
> }
>
> out:
> - WARN_ON(best_cpu > num_present_cpus() && best_cpu != -1);
> + WARN_ON(!cpu_present(best_cpu) && best_cpu != -1);
>
> return best_cpu;
> }
> @@ -137,7 +137,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
> int old_idx, new_cpu;
> unsigned long flags;
>
> - WARN_ON(cpu > num_present_cpus());
> + WARN_ON(!cpu_present(cpu));
>
> raw_spin_lock_irqsave(&cp->lock, flags);
> old_idx = cp->cpu_to_idx[cpu];
> --
> 1.8.1.4
>

2014-02-17 15:49:18

by Juri Lelli

Subject: Re: [PATCH] sched/deadline: Test for CPU's presence explicitly

On 02/17/2014 03:50 PM, Peter Zijlstra wrote:
> On Mon, Feb 17, 2014 at 09:12:33AM -0500, Boris Ostrovsky wrote:
>> A hot-removed CPU may have ID that is numerically larger than the number of
>> existing CPUs in the system (e.g. we can unplug CPU 4 from a system that
>> has CPUs 0, 1 and 4).
>>
>> Thus the WARN_ONs should check whether the CPU in question is currently
>> present, not whether its ID value is less than num_present_cpus().
>>
>> Reported-by: Konrad Rzeszutek Wilk <[email protected]>
>> Signed-off-by: Boris Ostrovsky <[email protected]>
>
> Thanks!, please also always CC the author of the code in question.
>

Thanks!

- Juri

>> ---
>> kernel/sched/cpudeadline.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
>> index 045fc74..5b8838b 100644
>> --- a/kernel/sched/cpudeadline.c
>> +++ b/kernel/sched/cpudeadline.c
>> @@ -70,7 +70,7 @@ static void cpudl_heapify(struct cpudl *cp, int idx)
>>
>> static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl)
>> {
>> - WARN_ON(idx > num_present_cpus() || idx == IDX_INVALID);
>> + WARN_ON(!cpu_present(idx) || idx == IDX_INVALID);
>>
>> if (dl_time_before(new_dl, cp->elements[idx].dl)) {
>> cp->elements[idx].dl = new_dl;
>> @@ -117,7 +117,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
>> }
>>
>> out:
>> - WARN_ON(best_cpu > num_present_cpus() && best_cpu != -1);
>> + WARN_ON(!cpu_present(best_cpu) && best_cpu != -1);
>>
>> return best_cpu;
>> }
>> @@ -137,7 +137,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
>> int old_idx, new_cpu;
>> unsigned long flags;
>>
>> - WARN_ON(cpu > num_present_cpus());
>> + WARN_ON(!cpu_present(cpu));
>>
>> raw_spin_lock_irqsave(&cp->lock, flags);
>> old_idx = cp->cpu_to_idx[cpu];
>> --
>> 1.8.1.4
>>

2014-02-21 20:33:27

by tip-bot for Vasyl Gomonovych

Subject: [tip:sched/urgent] sched/deadline: Test for CPU' s presence explicitly

Commit-ID: 82b95800b256205cff2eeab5bbd03430d2d0f20d
Gitweb: http://git.kernel.org/tip/82b95800b256205cff2eeab5bbd03430d2d0f20d
Author: Boris Ostrovsky <[email protected]>
AuthorDate: Mon, 17 Feb 2014 09:12:33 -0500
Committer: Thomas Gleixner <[email protected]>
CommitDate: Fri, 21 Feb 2014 21:27:10 +0100

sched/deadline: Test for CPU's presence explicitly

A hot-removed CPU may have ID that is numerically larger than the number of
existing CPUs in the system (e.g. we can unplug CPU 4 from a system that
has CPUs 0, 1 and 4).

Thus the WARN_ONs should check whether the CPU in question is currently
present, not whether its ID value is less than num_present_cpus().

Cc: Ingo Molnar <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Steven Rostedt <[email protected]>
Reported-by: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: Boris Ostrovsky <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
---
kernel/sched/cpudeadline.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 045fc74..5b8838b 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -70,7 +70,7 @@ static void cpudl_heapify(struct cpudl *cp, int idx)

static void cpudl_change_key(struct cpudl *cp, int idx, u64 new_dl)
{
- WARN_ON(idx > num_present_cpus() || idx == IDX_INVALID);
+ WARN_ON(!cpu_present(idx) || idx == IDX_INVALID);

if (dl_time_before(new_dl, cp->elements[idx].dl)) {
cp->elements[idx].dl = new_dl;
@@ -117,7 +117,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
}

out:
- WARN_ON(best_cpu > num_present_cpus() && best_cpu != -1);
+ WARN_ON(!cpu_present(best_cpu) && best_cpu != -1);

return best_cpu;
}
@@ -137,7 +137,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
int old_idx, new_cpu;
unsigned long flags;

- WARN_ON(cpu > num_present_cpus());
+ WARN_ON(!cpu_present(cpu));

raw_spin_lock_irqsave(&cp->lock, flags);
old_idx = cp->cpu_to_idx[cpu];