On Fri, May 31, 2024 at 04:07:32PM -0400, Waiman Long wrote: > > On 5/26/24 14:35, Tejun Heo wrote: > > On Sat, May 25, 2024 at 09:46:48AM +0000, Xiu Jianfeng wrote: > > > 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<xiujianfeng@xxxxxxxxxx> > > > --- > > > 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); > > The code looks weird to me. It's doing the same thing under the > > is_in_v2_mode() block and the cgroup_subsys_on_dfl() block and the former is > > also run when the latter condition is true. Looks like we can get rid of the > > latter block? Waiman? > > Sorry for the late reply. > > The handling of the CS_SCHED_LOAD_BALANCE flag is different between v1 and > v2. For v1, CS_SCHED_LOAD_BALANCE is default to ON unless it is explicitly > turned off by writing to cpuset.sched_load_balance. For v2, the state will > follow its parent when a new cpuset is brought online. Since is_in_v2_mode() > can be on with cgroup v1, we can't group the two together. > > I agree that we don't need to protect the clearing of CS_SCHED_LOAD_BALANCE > with the callback lock. So I don't have objection to this patch. > > Acked-by: Waiman Long <longman@xxxxxxxxxx> Applied to cgroup/for-6.11. Thanks. -- tejun
