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

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Message-ID: <e97d96fc-cbdf-4c03-aa1a-b0cde5419681@redhat.com>
Date: Sun, 11 Jan 2026 20:43:16 -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 1/1/26 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.

Cheers,
Longman