Re: [PATCH v0] cgroup: Add lock guard support

[Jemmy Wong <jemmywong512@gmail.com>]

Hi Michal,

> On Jun 6, 2025, at 5:34 PM, Michal Koutný <mkoutny@suse.com> wrote:
> 
> Hello.
> 
> On Fri, Jun 06, 2025 at 05:10:53AM +0800, Jemmy Wong <jemmywong512@gmail.com> wrote:
>> This change replaces manual lock acquisition and release with lock guards
>> to improve code robustness and reduce the risk of lock mismanagement.
>> No functional changes to the cgroup logic are introduced.
> 
> I like this.
> Could you possible split it to individual commits to ease the review
> for: cgroup_mutex, css_set_lock, RCU and the rest?
> 

Thanks for your support. I’ll split the patch into several parts.

> ...
>> --- a/include/linux/cgroup.h
>> +++ b/include/linux/cgroup.h
>> @@ -382,6 +382,10 @@ static inline void cgroup_put(struct cgroup *cgrp)
>> 
>> extern struct mutex cgroup_mutex;
>> 
>> +DEFINE_LOCK_GUARD_0(cgroup_mutex,
>> + mutex_lock(&cgroup_mutex),
>> + mutex_unlock(&cgroup_mutex))
>> +
>> static inline void cgroup_lock(void)
>> {
>> mutex_lock(&cgroup_mutex);
>> @@ -656,6 +660,9 @@ struct cgroup *cgroup_get_from_id(u64 id);
>> struct cgroup_subsys_state;
>> struct cgroup;
>> 
>> +extern struct mutex cgroup_mutex;
> 
> I assume this was because of the BPF code, which wouldn't be needed in
> the end.
> 

Yeah, other modules also need cgroup_mutex, cgroup_lock/unlock must be retained.

> ...
> 
> Thanks,
> Michal

Best, 
Jemmy