sched: cgroup: Move task_can_attach() to cpuset.c

[PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Steven Rostedt 2 months, 2 weeks ago

From: Steven Rostedt <rostedt@goodmis.org>

At our monthly stable meeting, we were talking about documenting non
static functions and randomly picked a function to look at. That was
task_can_attach(). It was then noticed that it's only used by
cgroup/cpuset.c and nothing else. It's a simple function that doesn't
reference anything unique to sched/core.c, hence there's no reason that
function should be there.

Move it to cgroup/cpuset.c as that's the only place it is used. Also make
it a static inline as it is so small.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 include/linux/sched.h  |  1 -
 kernel/cgroup/cpuset.c | 19 +++++++++++++++++++
 kernel/sched/core.c    | 19 -------------------
 3 files changed, 19 insertions(+), 20 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e4ce0a76831e..4ee4fa973eda 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1849,7 +1849,6 @@ current_restore_flags(unsigned long orig_flags, unsigned long flags)
 }
 
 extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial);
-extern int task_can_attach(struct task_struct *p);
 extern int dl_bw_alloc(int cpu, u64 dl_bw);
 extern void dl_bw_free(int cpu, u64 dl_bw);
 
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 27adb04df675..21fe872803e8 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3009,6 +3009,25 @@ static void reset_migrate_dl_data(struct cpuset *cs)
 	cs->sum_migrate_dl_bw = 0;
 }
 
+static inline int task_can_attach(struct task_struct *p)
+{
+	int ret = 0;
+
+	/*
+	 * Kthreads which disallow setaffinity shouldn't be moved
+	 * to a new cpuset; we don't want to change their CPU
+	 * affinity and isolating such threads by their set of
+	 * allowed nodes is unnecessary.  Thus, cpusets are not
+	 * applicable for such threads.  This prevents checking for
+	 * success of set_cpus_allowed_ptr() on all attached tasks
+	 * before cpus_mask may be changed.
+	 */
+	if (p->flags & PF_NO_SETAFFINITY)
+		ret = -EINVAL;
+
+	return ret;
+}
+
 /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
 static int cpuset_can_attach(struct cgroup_taskset *tset)
 {
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ccba6fc3c3fe..a195c4b25475 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8070,25 +8070,6 @@ int cpuset_cpumask_can_shrink(const struct cpumask *cur,
 	return ret;
 }
 
-int task_can_attach(struct task_struct *p)
-{
-	int ret = 0;
-
-	/*
-	 * Kthreads which disallow setaffinity shouldn't be moved
-	 * to a new cpuset; we don't want to change their CPU
-	 * affinity and isolating such threads by their set of
-	 * allowed nodes is unnecessary.  Thus, cpusets are not
-	 * applicable for such threads.  This prevents checking for
-	 * success of set_cpus_allowed_ptr() on all attached tasks
-	 * before cpus_mask may be changed.
-	 */
-	if (p->flags & PF_NO_SETAFFINITY)
-		ret = -EINVAL;
-
-	return ret;
-}
-
 bool sched_smp_initialized __read_mostly;
 
 #ifdef CONFIG_NUMA_BALANCING
-- 
2.50.1

Re: [PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Tejun Heo 2 months, 2 weeks ago

On Fri, Oct 03, 2025 at 12:14:21PM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
> 
> At our monthly stable meeting, we were talking about documenting non
> static functions and randomly picked a function to look at. That was
> task_can_attach(). It was then noticed that it's only used by
> cgroup/cpuset.c and nothing else. It's a simple function that doesn't
> reference anything unique to sched/core.c, hence there's no reason that
> function should be there.
> 
> Move it to cgroup/cpuset.c as that's the only place it is used. Also make
> it a static inline as it is so small.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Peter, if it looks good to you, I can route it through cgroup tree.

Thanks.

-- 
tejun

Re: [PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Peter Zijlstra 2 months, 1 week ago

On Fri, Oct 03, 2025 at 11:38:09AM -1000, Tejun Heo wrote:
> On Fri, Oct 03, 2025 at 12:14:21PM -0400, Steven Rostedt wrote:
> > From: Steven Rostedt <rostedt@goodmis.org>
> > 
> > At our monthly stable meeting, we were talking about documenting non
> > static functions and randomly picked a function to look at. That was
> > task_can_attach(). It was then noticed that it's only used by
> > cgroup/cpuset.c and nothing else. It's a simple function that doesn't
> > reference anything unique to sched/core.c, hence there's no reason that
> > function should be there.
> > 
> > Move it to cgroup/cpuset.c as that's the only place it is used. Also make
> > it a static inline as it is so small.
> > 
> > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> 
> Peter, if it looks good to you, I can route it through cgroup tree.

Yeah, I suppose so. But there were suggested changes to the Changelog
and actual patch so perhaps wait for v2?

Re: [PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Tejun Heo 2 months, 1 week ago

On Mon, Oct 06, 2025 at 08:31:59PM +0200, Peter Zijlstra wrote:
> On Fri, Oct 03, 2025 at 11:38:09AM -1000, Tejun Heo wrote:
> > On Fri, Oct 03, 2025 at 12:14:21PM -0400, Steven Rostedt wrote:
> > > From: Steven Rostedt <rostedt@goodmis.org>
> > > 
> > > At our monthly stable meeting, we were talking about documenting non
> > > static functions and randomly picked a function to look at. That was
> > > task_can_attach(). It was then noticed that it's only used by
> > > cgroup/cpuset.c and nothing else. It's a simple function that doesn't
> > > reference anything unique to sched/core.c, hence there's no reason that
> > > function should be there.
> > > 
> > > Move it to cgroup/cpuset.c as that's the only place it is used. Also make
> > > it a static inline as it is so small.
> > > 
> > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> > 
> > Peter, if it looks good to you, I can route it through cgroup tree.
> 
> Yeah, I suppose so. But there were suggested changes to the Changelog
> and actual patch so perhaps wait for v2?

Yeah, will wait for v2 and then apply it.

Thanks.

-- 
tejun

Re: [External] : [PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Joseph Salisbury 2 months, 2 weeks ago


On 10/3/25 12:14, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
>
> At our monthly stable meeting, we were talking about documenting non
> static functions and randomly picked a function to look at. That was
> task_can_attach(). It was then noticed that it's only used by
> cgroup/cpuset.c and nothing else. It's a simple function that doesn't
> reference anything unique to sched/core.c, hence there's no reason that
> function should be there.
>
> Move it to cgroup/cpuset.c as that's the only place it is used. Also make
> it a static inline as it is so small.
>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>   include/linux/sched.h  |  1 -
>   kernel/cgroup/cpuset.c | 19 +++++++++++++++++++
>   kernel/sched/core.c    | 19 -------------------
>   3 files changed, 19 insertions(+), 20 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index e4ce0a76831e..4ee4fa973eda 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1849,7 +1849,6 @@ current_restore_flags(unsigned long orig_flags, unsigned long flags)
>   }
>   
>   extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial);
> -extern int task_can_attach(struct task_struct *p);
>   extern int dl_bw_alloc(int cpu, u64 dl_bw);
>   extern void dl_bw_free(int cpu, u64 dl_bw);
>   
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 27adb04df675..21fe872803e8 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -3009,6 +3009,25 @@ static void reset_migrate_dl_data(struct cpuset *cs)
>   	cs->sum_migrate_dl_bw = 0;
>   }
>   
> +static inline int task_can_attach(struct task_struct *p)
> +{
> +	int ret = 0;
> +
> +	/*
> +	 * Kthreads which disallow setaffinity shouldn't be moved
> +	 * to a new cpuset; we don't want to change their CPU
> +	 * affinity and isolating such threads by their set of
> +	 * allowed nodes is unnecessary.  Thus, cpusets are not
> +	 * applicable for such threads.  This prevents checking for
> +	 * success of set_cpus_allowed_ptr() on all attached tasks
> +	 * before cpus_mask may be changed.
> +	 */
> +	if (p->flags & PF_NO_SETAFFINITY)
> +		ret = -EINVAL;
> +
> +	return ret;
> +}
> +
>   /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
>   static int cpuset_can_attach(struct cgroup_taskset *tset)
>   {
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ccba6fc3c3fe..a195c4b25475 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8070,25 +8070,6 @@ int cpuset_cpumask_can_shrink(const struct cpumask *cur,
>   	return ret;
>   }
>   
> -int task_can_attach(struct task_struct *p)
> -{
> -	int ret = 0;
> -
> -	/*
> -	 * Kthreads which disallow setaffinity shouldn't be moved
> -	 * to a new cpuset; we don't want to change their CPU
> -	 * affinity and isolating such threads by their set of
> -	 * allowed nodes is unnecessary.  Thus, cpusets are not
> -	 * applicable for such threads.  This prevents checking for
> -	 * success of set_cpus_allowed_ptr() on all attached tasks
> -	 * before cpus_mask may be changed.
> -	 */
> -	if (p->flags & PF_NO_SETAFFINITY)
> -		ret = -EINVAL;
> -
> -	return ret;
> -}
> -
>   bool sched_smp_initialized __read_mostly;
>   
>   #ifdef CONFIG_NUMA_BALANCING
Nice beneficial refactoring!

Reviewed-by: Joseph Salisbury <joseph.salisbury@oracle.com>

Re: [PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Luis Claudio R. Goncalves 2 months, 2 weeks ago

On Fri, Oct 03, 2025 at 12:14:21PM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
> 
> At our monthly stable meeting, we were talking about documenting non
> static functions and randomly picked a function to look at. That was
> task_can_attach(). It was then noticed that it's only used by
> cgroup/cpuset.c and nothing else. It's a simple function that doesn't
> reference anything unique to sched/core.c, hence there's no reason that
> function should be there.
> 
> Move it to cgroup/cpuset.c as that's the only place it is used. Also make
> it a static inline as it is so small.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  include/linux/sched.h  |  1 -
>  kernel/cgroup/cpuset.c | 19 +++++++++++++++++++
>  kernel/sched/core.c    | 19 -------------------
>  3 files changed, 19 insertions(+), 20 deletions(-)

That was a fun exercise. :)

Tested-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>

Re: [PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Waiman Long 2 months, 2 weeks ago

On 10/3/25 12:14 PM, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
>
> At our monthly stable meeting, we were talking about documenting non
> static functions and randomly picked a function to look at. That was
> task_can_attach(). It was then noticed that it's only used by
> cgroup/cpuset.c and nothing else. It's a simple function that doesn't
> reference anything unique to sched/core.c, hence there's no reason that
> function should be there.
>
> Move it to cgroup/cpuset.c as that's the only place it is used. Also make
> it a static inline as it is so small.
>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>   include/linux/sched.h  |  1 -
>   kernel/cgroup/cpuset.c | 19 +++++++++++++++++++
>   kernel/sched/core.c    | 19 -------------------
>   3 files changed, 19 insertions(+), 20 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index e4ce0a76831e..4ee4fa973eda 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1849,7 +1849,6 @@ current_restore_flags(unsigned long orig_flags, unsigned long flags)
>   }
>   
>   extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial);
> -extern int task_can_attach(struct task_struct *p);
>   extern int dl_bw_alloc(int cpu, u64 dl_bw);
>   extern void dl_bw_free(int cpu, u64 dl_bw);
>   
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 27adb04df675..21fe872803e8 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -3009,6 +3009,25 @@ static void reset_migrate_dl_data(struct cpuset *cs)
>   	cs->sum_migrate_dl_bw = 0;
>   }
>   
> +static inline int task_can_attach(struct task_struct *p)
> +{
> +	int ret = 0;
> +
> +	/*
> +	 * Kthreads which disallow setaffinity shouldn't be moved
> +	 * to a new cpuset; we don't want to change their CPU
> +	 * affinity and isolating such threads by their set of
> +	 * allowed nodes is unnecessary.  Thus, cpusets are not
> +	 * applicable for such threads.  This prevents checking for
> +	 * success of set_cpus_allowed_ptr() on all attached tasks
> +	 * before cpus_mask may be changed.
> +	 */
> +	if (p->flags & PF_NO_SETAFFINITY)
> +		ret = -EINVAL;
> +
> +	return ret;
> +}
> +
>   /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
>   static int cpuset_can_attach(struct cgroup_taskset *tset)
>   {
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ccba6fc3c3fe..a195c4b25475 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8070,25 +8070,6 @@ int cpuset_cpumask_can_shrink(const struct cpumask *cur,
>   	return ret;
>   }
>   
> -int task_can_attach(struct task_struct *p)
> -{
> -	int ret = 0;
> -
> -	/*
> -	 * Kthreads which disallow setaffinity shouldn't be moved
> -	 * to a new cpuset; we don't want to change their CPU
> -	 * affinity and isolating such threads by their set of
> -	 * allowed nodes is unnecessary.  Thus, cpusets are not
> -	 * applicable for such threads.  This prevents checking for
> -	 * success of set_cpus_allowed_ptr() on all attached tasks
> -	 * before cpus_mask may be changed.
> -	 */
> -	if (p->flags & PF_NO_SETAFFINITY)
> -		ret = -EINVAL;
> -
> -	return ret;
> -}
> -
>   bool sched_smp_initialized __read_mostly;
>   
>   #ifdef CONFIG_NUMA_BALANCING
Acked-by: Waiman Long <longman@redhat.com>

Re: [PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Andrea Righi 2 months, 2 weeks ago

Hi Steven,

On Fri, Oct 03, 2025 at 12:14:21PM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
> 
> At our monthly stable meeting, we were talking about documenting non
> static functions and randomly picked a function to look at. That was
> task_can_attach(). It was then noticed that it's only used by
> cgroup/cpuset.c and nothing else. It's a simple function that doesn't
> reference anything unique to sched/core.c, hence there's no reason that
> function should be there.
> 
> Move it to cgroup/cpuset.c as that's the only place it is used. Also make
> it a static inline as it is so small.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Nice cleanup. :)

Apparently it became that small with commit 2ef269ef1ac00 ("cgroup/cpuset:
Free DL BW in case can_attach() fails"), maybe we can mention that in the
commit message?

> ---
>  include/linux/sched.h  |  1 -
>  kernel/cgroup/cpuset.c | 19 +++++++++++++++++++
>  kernel/sched/core.c    | 19 -------------------
>  3 files changed, 19 insertions(+), 20 deletions(-)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index e4ce0a76831e..4ee4fa973eda 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1849,7 +1849,6 @@ current_restore_flags(unsigned long orig_flags, unsigned long flags)
>  }
>  
>  extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial);
> -extern int task_can_attach(struct task_struct *p);
>  extern int dl_bw_alloc(int cpu, u64 dl_bw);
>  extern void dl_bw_free(int cpu, u64 dl_bw);
>  
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 27adb04df675..21fe872803e8 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -3009,6 +3009,25 @@ static void reset_migrate_dl_data(struct cpuset *cs)
>  	cs->sum_migrate_dl_bw = 0;
>  }
>  
> +static inline int task_can_attach(struct task_struct *p)
> +{
> +	int ret = 0;
> +
> +	/*
> +	 * Kthreads which disallow setaffinity shouldn't be moved
> +	 * to a new cpuset; we don't want to change their CPU
> +	 * affinity and isolating such threads by their set of
> +	 * allowed nodes is unnecessary.  Thus, cpusets are not
> +	 * applicable for such threads.  This prevents checking for
> +	 * success of set_cpus_allowed_ptr() on all attached tasks
> +	 * before cpus_mask may be changed.
> +	 */
> +	if (p->flags & PF_NO_SETAFFINITY)
> +		ret = -EINVAL;
> +
> +	return ret;

As we're cleaning up, we could just return -EINVAL and 0 directly and get
rid of that ret variable.

> +}
> +
>  /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
>  static int cpuset_can_attach(struct cgroup_taskset *tset)
>  {
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ccba6fc3c3fe..a195c4b25475 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -8070,25 +8070,6 @@ int cpuset_cpumask_can_shrink(const struct cpumask *cur,
>  	return ret;
>  }
>  
> -int task_can_attach(struct task_struct *p)
> -{
> -	int ret = 0;
> -
> -	/*
> -	 * Kthreads which disallow setaffinity shouldn't be moved
> -	 * to a new cpuset; we don't want to change their CPU
> -	 * affinity and isolating such threads by their set of
> -	 * allowed nodes is unnecessary.  Thus, cpusets are not
> -	 * applicable for such threads.  This prevents checking for
> -	 * success of set_cpus_allowed_ptr() on all attached tasks
> -	 * before cpus_mask may be changed.
> -	 */
> -	if (p->flags & PF_NO_SETAFFINITY)
> -		ret = -EINVAL;
> -
> -	return ret;
> -}
> -
>  bool sched_smp_initialized __read_mostly;
>  
>  #ifdef CONFIG_NUMA_BALANCING
> -- 
> 2.50.1
> 

Thanks,
-Andrea

Re: [PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Steven Rostedt 2 months, 2 weeks ago

On Fri, 3 Oct 2025 18:36:24 +0200
Andrea Righi <arighi@nvidia.com> wrote:

> Hi Steven,
> 
> On Fri, Oct 03, 2025 at 12:14:21PM -0400, Steven Rostedt wrote:
> > From: Steven Rostedt <rostedt@goodmis.org>
> > 
> > At our monthly stable meeting, we were talking about documenting non
> > static functions and randomly picked a function to look at. That was
> > task_can_attach(). It was then noticed that it's only used by
> > cgroup/cpuset.c and nothing else. It's a simple function that doesn't
> > reference anything unique to sched/core.c, hence there's no reason that
> > function should be there.
> > 
> > Move it to cgroup/cpuset.c as that's the only place it is used. Also make
> > it a static inline as it is so small.
> > 
> > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>  
> 
> Nice cleanup. :)

Thanks, since you also were the first to notice it is only used in one spot.

> 
> Apparently it became that small with commit 2ef269ef1ac00 ("cgroup/cpuset:
> Free DL BW in case can_attach() fails"), maybe we can mention that in the
> commit message?

Sure.

> 
> > ---
> >  include/linux/sched.h  |  1 -
> >  kernel/cgroup/cpuset.c | 19 +++++++++++++++++++
> >  kernel/sched/core.c    | 19 -------------------
> >  3 files changed, 19 insertions(+), 20 deletions(-)
> > 
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index e4ce0a76831e..4ee4fa973eda 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -1849,7 +1849,6 @@ current_restore_flags(unsigned long orig_flags, unsigned long flags)
> >  }
> >  
> >  extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial);
> > -extern int task_can_attach(struct task_struct *p);
> >  extern int dl_bw_alloc(int cpu, u64 dl_bw);
> >  extern void dl_bw_free(int cpu, u64 dl_bw);
> >  
> > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> > index 27adb04df675..21fe872803e8 100644
> > --- a/kernel/cgroup/cpuset.c
> > +++ b/kernel/cgroup/cpuset.c
> > @@ -3009,6 +3009,25 @@ static void reset_migrate_dl_data(struct cpuset *cs)
> >  	cs->sum_migrate_dl_bw = 0;
> >  }
> >  
> > +static inline int task_can_attach(struct task_struct *p)
> > +{
> > +	int ret = 0;
> > +
> > +	/*
> > +	 * Kthreads which disallow setaffinity shouldn't be moved
> > +	 * to a new cpuset; we don't want to change their CPU
> > +	 * affinity and isolating such threads by their set of
> > +	 * allowed nodes is unnecessary.  Thus, cpusets are not
> > +	 * applicable for such threads.  This prevents checking for
> > +	 * success of set_cpus_allowed_ptr() on all attached tasks
> > +	 * before cpus_mask may be changed.
> > +	 */
> > +	if (p->flags & PF_NO_SETAFFINITY)
> > +		ret = -EINVAL;
> > +
> > +	return ret;  
> 
> As we're cleaning up, we could just return -EINVAL and 0 directly and get
> rid of that ret variable.

That should be a separate patch. Moves should really not do much else. I
even wondered about making it a static inline too, but figured that wasn't
touching the logic, and the function was going to become static anyway.

-- Steve


> 
> > +}
> > +
> >  /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
> >  static int cpuset_can_attach(struct cgroup_taskset *tset)
> >  {
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index ccba6fc3c3fe..a195c4b25475 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -8070,25 +8070,6 @@ int cpuset_cpumask_can_shrink(const struct cpumask *cur,
> >  	return ret;
> >  }
> >  
> > -int task_can_attach(struct task_struct *p)
> > -{
> > -	int ret = 0;
> > -
> > -	/*
> > -	 * Kthreads which disallow setaffinity shouldn't be moved
> > -	 * to a new cpuset; we don't want to change their CPU
> > -	 * affinity and isolating such threads by their set of
> > -	 * allowed nodes is unnecessary.  Thus, cpusets are not
> > -	 * applicable for such threads.  This prevents checking for
> > -	 * success of set_cpus_allowed_ptr() on all attached tasks
> > -	 * before cpus_mask may be changed.
> > -	 */
> > -	if (p->flags & PF_NO_SETAFFINITY)
> > -		ret = -EINVAL;
> > -
> > -	return ret;
> > -}
> > -
> >  bool sched_smp_initialized __read_mostly;
> >  
> >  #ifdef CONFIG_NUMA_BALANCING
> > -- 
> > 2.50.1
> >   
> 
> Thanks,
> -Andrea

Re: [PATCH] sched: cgroup: Move task_can_attach() to cpuset.c

Posted by Andrea Righi 2 months, 2 weeks ago

On Fri, Oct 03, 2025 at 12:43:00PM -0400, Steven Rostedt wrote:
...
> > > +static inline int task_can_attach(struct task_struct *p)
> > > +{
> > > +	int ret = 0;
> > > +
> > > +	/*
> > > +	 * Kthreads which disallow setaffinity shouldn't be moved
> > > +	 * to a new cpuset; we don't want to change their CPU
> > > +	 * affinity and isolating such threads by their set of
> > > +	 * allowed nodes is unnecessary.  Thus, cpusets are not
> > > +	 * applicable for such threads.  This prevents checking for
> > > +	 * success of set_cpus_allowed_ptr() on all attached tasks
> > > +	 * before cpus_mask may be changed.
> > > +	 */
> > > +	if (p->flags & PF_NO_SETAFFINITY)
> > > +		ret = -EINVAL;
> > > +
> > > +	return ret;  
> > 
> > As we're cleaning up, we could just return -EINVAL and 0 directly and get
> > rid of that ret variable.
> 
> That should be a separate patch. Moves should really not do much else. I
> even wondered about making it a static inline too, but figured that wasn't
> touching the logic, and the function was going to become static anyway.

Oh yes, good point. In the meantime, FWIW:

Tested-by: Andrea Righi <arighi@nvidia.com>

Thanks,
-Andrea