Re: [PATCH 11/33] cpuset: Provide lockdep check for cpuset lock held

Chen Ridong
2025-10-14T13:29:31Z

On 2025/10/14 4:31, 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@kernel.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 2ddb256187b5..051d36fec578 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 8595f1eadf23..aa1ac7bcf2ea 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -279,6 +279,13 @@ 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)

Is the lockdep_is_cpuset_held function actually being used?
If CONFIG_LOCKDEP is disabled, compilation would fail with an "undefined reference to
lockdep_is_cpuset_held" error.

--
Best regards,
Ridong