In set_cpus_allowed_force() we use kfree_rcu() because kfree() is unsafe under p->pi_lock.
With kfree_nolock() now being able to free arbitrary kmalloc() objects, we can switch to kfree_nolock() and avoid the unnecessary rcu grace period delay. Only in some cases the freeing might be deferred to irq_work(). Signed-off-by: Vlastimil Babka (SUSE) <[email protected]> --- kernel/sched/core.c | 9 ++------- kernel/sched/sched.h | 7 +------ 2 files changed, 3 insertions(+), 13 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 96226707c2f6..d2929e4e23f1 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2807,20 +2807,15 @@ void set_cpus_allowed_force(struct task_struct *p, const struct cpumask *new_mas .user_mask = NULL, .flags = SCA_USER, /* clear the user requested mask */ }; - union cpumask_rcuhead { - cpumask_t cpumask; - struct rcu_head rcu; - }; scoped_guard (__task_rq_lock, p) do_set_cpus_allowed(p, &ac); /* * Because this is called with p->pi_lock held, it is not possible - * to use kfree() here (when PREEMPT_RT=y), therefore punt to using - * kfree_rcu(). + * to use kfree() here (when PREEMPT_RT=y), thus use kfree_nolock() */ - kfree_rcu((union cpumask_rcuhead *)ac.user_mask, rcu); + kfree_nolock(ac.user_mask); } int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src, diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 56acf502ba26..6a8d0578e963 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2886,12 +2886,7 @@ static inline bool task_allowed_on_cpu(struct task_struct *p, int cpu) static inline cpumask_t *alloc_user_cpus_ptr(int node) { - /* - * See set_cpus_allowed_force() above for the rcu_head usage. - */ - int size = max_t(int, cpumask_size(), sizeof(struct rcu_head)); - - return kmalloc_node(size, GFP_KERNEL, node); + return kmalloc_node(cpumask_size(), GFP_KERNEL, node); } static inline struct task_struct *get_push_task(struct rq *rq) -- 2.55.0
