Commit b90ca8ba authored by Will Deacon's avatar Will Deacon Committed by Peter Zijlstra
Browse files

sched: Introduce task_struct::user_cpus_ptr to track requested affinity 



In preparation for saving and restoring the user-requested CPU affinity
mask of a task, add a new cpumask_t pointer to 'struct task_struct'.

If the pointer is non-NULL, then the mask is copied across fork() and
freed on task exit.

Signed-off-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarValentin Schneider <Valentin.Schneider@arm.com>
Link: https://lore.kernel.org/r/20210730112443.23245-7-will@kernel.org
parent 234a503e

include/linux/sched.h

+13 −0
Original line number Diff line number Diff line
@@ -748,6 +748,7 @@ struct task_struct { 
	unsigned int			policy;

	int				nr_cpus_allowed;

	const cpumask_t			*cpus_ptr;

	cpumask_t			*user_cpus_ptr;

	cpumask_t			cpus_mask;

	void				*migration_pending;

#ifdef CONFIG_SMP
@@ -1706,6 +1707,8 @@ extern int task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_ 
#ifdef CONFIG_SMP

extern void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask);

extern int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask);

extern int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src, int node);

extern void release_user_cpus_ptr(struct task_struct *p);

#else

static inline void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)

{
@@ -1716,6 +1719,16 @@ static inline int set_cpus_allowed_ptr(struct task_struct *p, const struct cpuma 
		return -EINVAL;

	return 0;

}

static inline int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src, int node)

{

	if (src->user_cpus_ptr)

		return -EINVAL;

	return 0;

}

static inline void release_user_cpus_ptr(struct task_struct *p)

{

	WARN_ON(p->user_cpus_ptr);

}

#endif



extern int yield_to(struct task_struct *p, bool preempt);

init/init_task.c

+1 −0
Original line number Diff line number Diff line
@@ -80,6 +80,7 @@ struct task_struct init_task 
	.normal_prio	= MAX_PRIO - 20,

	.policy		= SCHED_NORMAL,

	.cpus_ptr	= &init_task.cpus_mask,

	.user_cpus_ptr	= NULL,

	.cpus_mask	= CPU_MASK_ALL,

	.nr_cpus_allowed= NR_CPUS,

	.mm		= NULL,

kernel/fork.c

+2 −0
Original line number Diff line number Diff line
@@ -446,6 +446,7 @@ void put_task_stack(struct task_struct *tsk) 


void free_task(struct task_struct *tsk)

{

	release_user_cpus_ptr(tsk);

	scs_release(tsk);



#ifndef CONFIG_THREAD_INFO_IN_TASK
@@ -919,6 +920,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) 
#endif

	if (orig->cpus_ptr == &orig->cpus_mask)

		tsk->cpus_ptr = &tsk->cpus_mask;

	dup_user_cpus_ptr(tsk, orig, node);



	/*

	 * One for the user space visible state that goes away when reaped.

kernel/sched/core.c

+20 −0
Original line number Diff line number Diff line
@@ -2480,6 +2480,26 @@ void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) 
	__do_set_cpus_allowed(p, new_mask, 0);

}



int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src,

		      int node)

{

	if (!src->user_cpus_ptr)

		return 0;



	dst->user_cpus_ptr = kmalloc_node(cpumask_size(), GFP_KERNEL, node);

	if (!dst->user_cpus_ptr)

		return -ENOMEM;



	cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr);

	return 0;

}



void release_user_cpus_ptr(struct task_struct *p)

{

	kfree(p->user_cpus_ptr);

	p->user_cpus_ptr = NULL;

}



/*

 * This function is wildly self concurrent; here be dragons.

 *