LinuxLists.cc - [PATCH] sched/core: Fix a missed update of user_cpus

2023-02-03 18:20:07

Subject: [PATCH] sched/core: Fix a missed update of user_cpus_ptr

Since commit 8f9ea86fdf99 ("sched: Always preserve the user requested
cpumask"), a successful call to sched_setaffinity() should always save
the user requested cpu affinity mask in a task's user_cpus_ptr. However,
when the given cpu mask is the same as the current one, user_cpus_ptr
is not updated. Fix this by saving the user mask in this case too.

Fixes: 8f9ea86fdf99 ("sched: Always preserve the user requested cpumask")
Signed-off-by: Waiman Long <[email protected]>
---
kernel/sched/core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 30d9752e2ca5..91255f791df3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2951,8 +2951,11 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
}

if (!(ctx->flags & SCA_MIGRATE_ENABLE)) {
- if (cpumask_equal(&p->cpus_mask, ctx->new_mask))
+ if (cpumask_equal(&p->cpus_mask, ctx->new_mask)) {
+ if (ctx->flags & SCA_USER)
+ swap(p->user_cpus_ptr, ctx->user_mask);
goto out;
+ }

if (WARN_ON_ONCE(p == current &&
is_migration_disabled(p) &&
--
2.31.1

2023-02-03 21:07:32

by Tejun Heo

[permalink] [raw]

Subject: Re: [PATCH] sched/core: Fix a missed update of user_cpus_ptr

On Fri, Feb 03, 2023 at 01:18:49PM -0500, Waiman Long wrote:
> Since commit 8f9ea86fdf99 ("sched: Always preserve the user requested
> cpumask"), a successful call to sched_setaffinity() should always save
> the user requested cpu affinity mask in a task's user_cpus_ptr. However,
> when the given cpu mask is the same as the current one, user_cpus_ptr
> is not updated. Fix this by saving the user mask in this case too.
>
> Fixes: 8f9ea86fdf99 ("sched: Always preserve the user requested cpumask")
> Signed-off-by: Waiman Long <[email protected]>
> ---
> kernel/sched/core.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 30d9752e2ca5..91255f791df3 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2951,8 +2951,11 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
> }
>
> if (!(ctx->flags & SCA_MIGRATE_ENABLE)) {
> - if (cpumask_equal(&p->cpus_mask, ctx->new_mask))
> + if (cpumask_equal(&p->cpus_mask, ctx->new_mask)) {
> + if (ctx->flags & SCA_USER)
> + swap(p->user_cpus_ptr, ctx->user_mask);
> goto out;
> + }
>
> if (WARN_ON_ONCE(p == current &&
> is_migration_disabled(p) &&

and this is for a separate bug and should go through the scheduler tree.

Thanks.

--
tejun

2023-02-03 22:15:29

by Waiman Long

[permalink] [raw]

Subject: Re: [PATCH] sched/core: Fix a missed update of user_cpus_ptr

On 2/3/23 16:04, Tejun Heo wrote:
> On Fri, Feb 03, 2023 at 01:18:49PM -0500, Waiman Long wrote:
>> Since commit 8f9ea86fdf99 ("sched: Always preserve the user requested
>> cpumask"), a successful call to sched_setaffinity() should always save
>> the user requested cpu affinity mask in a task's user_cpus_ptr. However,
>> when the given cpu mask is the same as the current one, user_cpus_ptr
>> is not updated. Fix this by saving the user mask in this case too.
>>
>> Fixes: 8f9ea86fdf99 ("sched: Always preserve the user requested cpumask")
>> Signed-off-by: Waiman Long <[email protected]>
>> ---
>> kernel/sched/core.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 30d9752e2ca5..91255f791df3 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -2951,8 +2951,11 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
>> }
>>
>> if (!(ctx->flags & SCA_MIGRATE_ENABLE)) {
>> - if (cpumask_equal(&p->cpus_mask, ctx->new_mask))
>> + if (cpumask_equal(&p->cpus_mask, ctx->new_mask)) {
>> + if (ctx->flags & SCA_USER)
>> + swap(p->user_cpus_ptr, ctx->user_mask);
>> goto out;
>> + }
>>
>> if (WARN_ON_ONCE(p == current &&
>> is_migration_disabled(p) &&
> and this is for a separate bug and should go through the scheduler tree.

Yes, this is for Peter to pick up.

Cheers,
Longman

2023-02-13 14:57:39

by Peter Zijlstra

[permalink] [raw]

Subject: Re: [PATCH] sched/core: Fix a missed update of user_cpus_ptr

2023-02-15 10:33:12

by tip-bot2 for Alexey Makhalov

[permalink] [raw]

Subject: [tip: sched/urgent] sched/core: Fix a missed update of user_cpus_ptr

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

Commit-ID: df14b7f9efcda35e59bb6f50351aac25c50f6e24
Gitweb: https://git.kernel.org/tip/df14b7f9efcda35e59bb6f50351aac25c50f6e24
Author: Waiman Long <[email protected]>
AuthorDate: Fri, 03 Feb 2023 13:18:49 -05:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Mon, 13 Feb 2023 16:36:14 +01:00

sched/core: Fix a missed update of user_cpus_ptr

Since commit 8f9ea86fdf99 ("sched: Always preserve the user requested
cpumask"), a successful call to sched_setaffinity() should always save
the user requested cpu affinity mask in a task's user_cpus_ptr. However,
when the given cpu mask is the same as the current one, user_cpus_ptr
is not updated. Fix this by saving the user mask in this case too.

Fixes: 8f9ea86fdf99 ("sched: Always preserve the user requested cpumask")
Signed-off-by: Waiman Long <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
kernel/sched/core.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e838feb..2a4918a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2951,8 +2951,11 @@ static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
}

if (!(ctx->flags & SCA_MIGRATE_ENABLE)) {
- if (cpumask_equal(&p->cpus_mask, ctx->new_mask))
+ if (cpumask_equal(&p->cpus_mask, ctx->new_mask)) {
+ if (ctx->flags & SCA_USER)
+ swap(p->user_cpus_ptr, ctx->user_mask);
goto out;
+ }

if (WARN_ON_ONCE(p == current &&
is_migration_disabled(p) &&