linux-kernel - Re: [PATCH 12/33] cpuset: Provide lockdep check for cpuset lock held

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Message-ID: <f8ca375e-9051-4c7c-880d-e56e07206788@redhat.com>
Date: Mon, 12 Jan 2026 12:53:49 -0500
From: Waiman Long <llong@...hat.com>
To: Frederic Weisbecker <frederic@...nel.org>,
 LKML <linux-kernel@...r.kernel.org>
Cc: Michal Koutný <mkoutny@...e.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Bjorn Helgaas <bhelgaas@...gle.com>,
 Catalin Marinas <catalin.marinas@....com>,
 Chen Ridong <chenridong@...wei.com>, Danilo Krummrich <dakr@...nel.org>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Gabriele Monaco <gmonaco@...hat.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Ingo Molnar <mingo@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
 Jens Axboe <axboe@...nel.dk>, Johannes Weiner <hannes@...xchg.org>,
 Lai Jiangshan <jiangshanlai@...il.com>,
 Marco Crivellari <marco.crivellari@...e.com>, Michal Hocko
 <mhocko@...e.com>, Muchun Song <muchun.song@...ux.dev>,
 Paolo Abeni <pabeni@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Phil Auld <pauld@...hat.com>, "Rafael J . Wysocki" <rafael@...nel.org>,
 Roman Gushchin <roman.gushchin@...ux.dev>,
 Shakeel Butt <shakeel.butt@...ux.dev>, Simon Horman <horms@...nel.org>,
 Tejun Heo <tj@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
 Vlastimil Babka <vbabka@...e.cz>, Will Deacon <will@...nel.org>,
 cgroups@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-block@...r.kernel.org, linux-mm@...ck.org, linux-pci@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH 12/33] cpuset: Provide lockdep check for cpuset lock held

On 1/11/26 8:43 PM, Waiman Long wrote:
> On 1/1/26 5:13 PM, Frederic Weisbecker wrote:
>> cpuset modifies partitions, including isolated, while holding the cpuset
>> mutex.
>>
>> This means that holding the cpuset mutex is safe to synchronize against
>> housekeeping cpumask changes.
>>
>> Provide a lockdep check to validate that.
>>
>> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
>> ---
>>   include/linux/cpuset.h | 2 ++
>>   kernel/cgroup/cpuset.c | 7 +++++++
>>   2 files changed, 9 insertions(+)
>>
>> diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
>> index a98d3330385c..1c49ffd2ca9b 100644
>> --- a/include/linux/cpuset.h
>> +++ b/include/linux/cpuset.h
>> @@ -18,6 +18,8 @@
>>   #include <linux/mmu_context.h>
>>   #include <linux/jump_label.h>
>>   +extern bool lockdep_is_cpuset_held(void);
>> +
>>   #ifdef CONFIG_CPUSETS
>>     /*
>> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
>> index 3afa72f8d579..5e2e3514c22e 100644
>> --- a/kernel/cgroup/cpuset.c
>> +++ b/kernel/cgroup/cpuset.c
>> @@ -283,6 +283,13 @@ void cpuset_full_unlock(void)
>>       cpus_read_unlock();
>>   }
>>   +#ifdef CONFIG_LOCKDEP
>> +bool lockdep_is_cpuset_held(void)
>> +{
>> +    return lockdep_is_held(&cpuset_mutex);
>> +}
>> +#endif
>> +
>>   static DEFINE_SPINLOCK(callback_lock);
>>     void cpuset_callback_lock_irq(void)
>
> The cgroup/for-next tree already have a similar 
> lockdep_assert_cpuset_lock_held() defined. So you can drop this patch 
> if this series won't land in the next merge window. 

Sorry, the other new lockdep API isn't exactly the same as what you 
propose here. So it is not a replacement for your use case. Sorry for 
the noise.

Cheers,
Longman