linux-kernel - Re: [PATCH -next] cgroup/cpuset: add dec_attach_in

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Message-ID: <b45c24d2-98ee-4ecc-8d7d-6ac5dfa65c17@redhat.com>
Date: Thu, 25 Jul 2024 15:07:56 -0400
From: Waiman Long <longman@...hat.com>
To: chenridong <chenridong@...wei.com>,
 Kamalesh Babulal <kamalesh.babulal@...cle.com>, tj@...nel.org,
 lizefan.x@...edance.com, hannes@...xchg.org, adityakali@...gle.com,
 sergeh@...nel.org, mkoutny@...e.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] cgroup/cpuset: add dec_attach_in_progress helper


On 7/25/24 07:40, chenridong wrote:
>
>
> On 2024/7/25 19:01, Kamalesh Babulal wrote:
>>
>>
>> On 7/25/24 7:25 AM, Chen Ridong wrote:
>>> There are several functions to decrease attach_in_progress, and they
>>> will wake up cpuset_attach_wq when attach_in_progress is zero. So,
>>> add a helper to make it concise.
>>>
>>> Signed-off-by: Chen Ridong <chenridong@...wei.com>
>>> ---
>>>   kernel/cgroup/cpuset.c | 28 +++++++++++++++-------------
>>>   1 file changed, 15 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>>> index d4322619e59a..c241845694ac 100644
>>> --- a/kernel/cgroup/cpuset.c
>>> +++ b/kernel/cgroup/cpuset.c
>>> @@ -490,6 +490,17 @@ static inline void 
>>> check_insane_mems_config(nodemask_t *nodes)
>>>       }
>>>   }
>>>   +/*
>>> + * decrease cs->attach_in_progress.
>>> + * wake_up cpuset_attach_wq if cs->attach_in_progress==0.
>>
>> In the description, adding locking constraint of cpuset_mutex would 
>> be helpful.
>> Something like "cpuset_mutex must be held by the caller."
>>
> Thank you, I will to that.
>>> + */
>>> +static inline void dec_attach_in_progress(struct cpuset *cs)
>>> +{
>>> +    cs->attach_in_progress--;
>>> +    if (!cs->attach_in_progress)
>>> +        wake_up(&cpuset_attach_wq);
>>> +}
>>> +

I would suggested a dec_attach_in_progress_locked() and a 
dec_attach_in_progress() helpers. The dec_attach_in_progress() helper 
acquires the cpuset_mutex and call dec_attach_in_progress_locked(). 
Inside the dec_attach_in_progress_locked(), you can either add a comment 
about requiring cpuset_mutex held or add a 
lockdep_assert_held(&cpuset_mutex).

Cheers,
Longman