[PATCH RESEND] sched/fair: Fix wrong cpu selecting from isolated domain

[PATCH RESEND] sched/fair: Fix wrong cpu selecting from isolated domain

[Xunlei Pang]

We've met problems that occasionally tasks with full cpumask
(e.g. by putting it into a cpuset or setting to full affinity)
were migrated to our isolated cpus in production environment.

After some analysis, we found that it is due to the current
select_idle_smt() not considering the sched_domain mask.

Steps to reproduce on my 31-CPU hyperthreads machine:
1. with boot parameter: "isolcpus=domain,2-31"
   (thread lists: 0,16 and 1,17)
2. cgcreate -g cpu:test; cgexec -g cpu:test "test_threads"
3. some threads will be migrated to the isolated cpu16~17.

Fix it by checking the valid domain mask in select_idle_smt().

Fixes: 10e2f1acd010 ("sched/core: Rewrite and improve select_idle_siblings())
Reported-by: Wetp Zhang <wetp.zy@linux.alibaba.com>
Reviewed-by: Jiang Biao <benbjiang@tencent.com>
Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
---
 kernel/sched/fair.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a68a05..fa942c4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6075,7 +6075,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
 /*
  * Scan the local SMT mask for idle CPUs.
  */
-static int select_idle_smt(struct task_struct *p, int target)
+static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
 	int cpu;
 
@@ -6083,7 +6083,8 @@ static int select_idle_smt(struct task_struct *p, int target)
 		return -1;
 
 	for_each_cpu(cpu, cpu_smt_mask(target)) {
-		if (!cpumask_test_cpu(cpu, p->cpus_ptr))
+		if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
+		    !cpumask_test_cpu(cpu, sched_domain_span(sd)))
 			continue;
 		if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
 			return cpu;
@@ -6099,7 +6100,7 @@ static inline int select_idle_core(struct task_struct *p, struct sched_domain *s
 	return -1;
 }
 
-static inline int select_idle_smt(struct task_struct *p, int target)
+static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
 	return -1;
 }
@@ -6274,7 +6275,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
 	if ((unsigned)i < nr_cpumask_bits)
 		return i;
 
-	i = select_idle_smt(p, target);
+	i = select_idle_smt(p, sd, target);
 	if ((unsigned)i < nr_cpumask_bits)
 		return i;
 
-- 
1.8.3.1

Re: [PATCH RESEND] sched/fair: Fix wrong cpu selecting from isolated domain

[Vincent Guittot]

On Thu, 24 Sep 2020 at 08:48, Xunlei Pang <xlpang@linux.alibaba.com> wrote:
>
> We've met problems that occasionally tasks with full cpumask
> (e.g. by putting it into a cpuset or setting to full affinity)
> were migrated to our isolated cpus in production environment.
>
> After some analysis, we found that it is due to the current
> select_idle_smt() not considering the sched_domain mask.
>
> Steps to reproduce on my 31-CPU hyperthreads machine:
> 1. with boot parameter: "isolcpus=domain,2-31"
>    (thread lists: 0,16 and 1,17)
> 2. cgcreate -g cpu:test; cgexec -g cpu:test "test_threads"
> 3. some threads will be migrated to the isolated cpu16~17.
>
> Fix it by checking the valid domain mask in select_idle_smt().
>
> Fixes: 10e2f1acd010 ("sched/core: Rewrite and improve select_idle_siblings())
> Reported-by: Wetp Zhang <wetp.zy@linux.alibaba.com>
> Reviewed-by: Jiang Biao <benbjiang@tencent.com>
> Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>

Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>

> ---
>  kernel/sched/fair.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1a68a05..fa942c4 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6075,7 +6075,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
>  /*
>   * Scan the local SMT mask for idle CPUs.
>   */
> -static int select_idle_smt(struct task_struct *p, int target)
> +static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
>  {
>         int cpu;
>
> @@ -6083,7 +6083,8 @@ static int select_idle_smt(struct task_struct *p, int target)
>                 return -1;
>
>         for_each_cpu(cpu, cpu_smt_mask(target)) {
> -               if (!cpumask_test_cpu(cpu, p->cpus_ptr))
> +               if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
> +                   !cpumask_test_cpu(cpu, sched_domain_span(sd)))
>                         continue;
>                 if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
>                         return cpu;
> @@ -6099,7 +6100,7 @@ static inline int select_idle_core(struct task_struct *p, struct sched_domain *s
>         return -1;
>  }
>
> -static inline int select_idle_smt(struct task_struct *p, int target)
> +static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
>  {
>         return -1;
>  }
> @@ -6274,7 +6275,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
>         if ((unsigned)i < nr_cpumask_bits)
>                 return i;
>
> -       i = select_idle_smt(p, target);
> +       i = select_idle_smt(p, sd, target);
>         if ((unsigned)i < nr_cpumask_bits)
>                 return i;
>
> --
> 1.8.3.1
>

Re: [PATCH RESEND] sched/fair: Fix wrong cpu selecting from isolated domain

[Xunlei Pang]

On 9/24/20 3:18 PM, Vincent Guittot wrote:
> On Thu, 24 Sep 2020 at 08:48, Xunlei Pang <xlpang@linux.alibaba.com> wrote:
>>
>> We've met problems that occasionally tasks with full cpumask
>> (e.g. by putting it into a cpuset or setting to full affinity)
>> were migrated to our isolated cpus in production environment.
>>
>> After some analysis, we found that it is due to the current
>> select_idle_smt() not considering the sched_domain mask.
>>
>> Steps to reproduce on my 31-CPU hyperthreads machine:
>> 1. with boot parameter: "isolcpus=domain,2-31"
>>    (thread lists: 0,16 and 1,17)
>> 2. cgcreate -g cpu:test; cgexec -g cpu:test "test_threads"
>> 3. some threads will be migrated to the isolated cpu16~17.
>>
>> Fix it by checking the valid domain mask in select_idle_smt().
>>
>> Fixes: 10e2f1acd010 ("sched/core: Rewrite and improve select_idle_siblings())
>> Reported-by: Wetp Zhang <wetp.zy@linux.alibaba.com>
>> Reviewed-by: Jiang Biao <benbjiang@tencent.com>
>> Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
> 
> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
> 

Thanks, Vincent :-)

[tip: sched/core] sched/fair: Fix wrong cpu selecting from isolated domain

[tip-bot2 for Xunlei Pang]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     df3cb4ea1fb63ff326488efd671ba3c39034255e
Gitweb:        https://git.kernel.org/tip/df3cb4ea1fb63ff326488efd671ba3c39034255e
Author:        Xunlei Pang <xlpang@linux.alibaba.com>
AuthorDate:    Thu, 24 Sep 2020 14:48:47 +08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 25 Sep 2020 14:23:25 +02:00

sched/fair: Fix wrong cpu selecting from isolated domain

We've met problems that occasionally tasks with full cpumask
(e.g. by putting it into a cpuset or setting to full affinity)
were migrated to our isolated cpus in production environment.

After some analysis, we found that it is due to the current
select_idle_smt() not considering the sched_domain mask.

Steps to reproduce on my 31-CPU hyperthreads machine:
1. with boot parameter: "isolcpus=domain,2-31"
   (thread lists: 0,16 and 1,17)
2. cgcreate -g cpu:test; cgexec -g cpu:test "test_threads"
3. some threads will be migrated to the isolated cpu16~17.

Fix it by checking the valid domain mask in select_idle_smt().

Fixes: 10e2f1acd010 ("sched/core: Rewrite and improve select_idle_siblings())
Reported-by: Wetp Zhang <wetp.zy@linux.alibaba.com>
Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Jiang Biao <benbjiang@tencent.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/1600930127-76857-1-git-send-email-xlpang@linux.alibaba.com
---
 kernel/sched/fair.c |  9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a15deb2..9613e5d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6080,7 +6080,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int 
 /*
  * Scan the local SMT mask for idle CPUs.
  */
-static int select_idle_smt(struct task_struct *p, int target)
+static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
 	int cpu;
 
@@ -6088,7 +6088,8 @@ static int select_idle_smt(struct task_struct *p, int target)
 		return -1;
 
 	for_each_cpu(cpu, cpu_smt_mask(target)) {
-		if (!cpumask_test_cpu(cpu, p->cpus_ptr))
+		if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
+		    !cpumask_test_cpu(cpu, sched_domain_span(sd)))
 			continue;
 		if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
 			return cpu;
@@ -6104,7 +6105,7 @@ static inline int select_idle_core(struct task_struct *p, struct sched_domain *s
 	return -1;
 }
 
-static inline int select_idle_smt(struct task_struct *p, int target)
+static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
 {
 	return -1;
 }
@@ -6279,7 +6280,7 @@ symmetric:
 	if ((unsigned)i < nr_cpumask_bits)
 		return i;
 
-	i = select_idle_smt(p, target);
+	i = select_idle_smt(p, sd, target);
 	if ((unsigned)i < nr_cpumask_bits)
 		return i;