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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: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Link: https://lore.kernel.org/r/20210730112443.23245-7-will@kernel.org
This commit is contained in:
Will Deacon 2021-07-30 12:24:33 +01:00 committed by Peter Zijlstra
parent 234a503e67
commit b90ca8badb
4 changed files with 36 additions and 0 deletions
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13
include/linux/sched.h
View File

@ -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);

1
init/init_task.c
View File

@ -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,

2
kernel/fork.c
View File

@ -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.

20
kernel/sched/core.c
View File

@ -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.
*