From 018ee567def3b43f810aebf15221eef3858177b2 Mon Sep 17 00:00:00 2001 From: Xiu Jianfeng Date: Sat, 25 May 2024 09:46:48 +0000 Subject: [PATCH] cgroup/cpuset: Reduce the lock protecting CS_SCHED_LOAD_BALANCE In the cpuset_css_online(), clearing the CS_SCHED_LOAD_BALANCE bit of cs->flags is guarded by callback_lock and cpuset_mutex. There is no problem with itself, because it is consistent with the description of there two global lock at the beginning of this file. However, since the operation of checking, setting and clearing the flag bit is atomic, protection of callback_lock is unnecessary here, see CS_SPREAD_*. so to make it more consistent with the other code, move the operation outside the critical section of callback_lock. No functional changes intended. Signed-off-by: Xiu Jianfeng Acked-by: Waiman Long Signed-off-by: Tejun Heo --- kernel/cgroup/cpuset.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index f9d2a3487645..315f8cbd6d35 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -4038,6 +4038,12 @@ static int cpuset_css_online(struct cgroup_subsys_state *css) set_bit(CS_SPREAD_PAGE, &cs->flags); if (is_spread_slab(parent)) set_bit(CS_SPREAD_SLAB, &cs->flags); + /* + * For v2, clear CS_SCHED_LOAD_BALANCE if parent is isolated + */ + if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) && + !is_sched_load_balance(parent)) + clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags); cpuset_inc(); @@ -4048,14 +4054,6 @@ static int cpuset_css_online(struct cgroup_subsys_state *css) cs->use_parent_ecpus = true; parent->child_ecpus_count++; } - - /* - * For v2, clear CS_SCHED_LOAD_BALANCE if parent is isolated - */ - if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) && - !is_sched_load_balance(parent)) - clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags); - spin_unlock_irq(&callback_lock); if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags))