[Nouveau] [RFC v4 02/12] kthread: Add kthread_(un)block_work_queuing() and kthread_work_queuable()

[William Lewis]

Minor nitpick.  s/queuing/queueing/ and s/queuable/queueable/.

On 2020-05-08 15:46, Lyude Paul wrote:
> Add some simple wrappers around incrementing/decrementing
> kthread_work.cancelling under lock, along with checking whether queuing
> is currently allowed on a given kthread_work, which we'll use want to
> implement work cancelling with DRM's vblank work helpers.
>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Tejun Heo <tj at kernel.org>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: dri-devel at lists.freedesktop.org
> Cc: nouveau at lists.freedesktop.org
> Signed-off-by: Lyude Paul <lyude at redhat.com>
> ---
>   include/linux/kthread.h | 19 +++++++++++++++++
>   kernel/kthread.c        | 46 +++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 65 insertions(+)
>
> diff --git a/include/linux/kthread.h b/include/linux/kthread.h
> index 0006540ce7f9..c6fee200fced 100644
> --- a/include/linux/kthread.h
> +++ b/include/linux/kthread.h
> @@ -211,9 +211,28 @@ void kthread_flush_worker(struct kthread_worker *worker);
>   
>   bool kthread_cancel_work_sync(struct kthread_work *work);
>   bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *work);
> +void kthread_block_work_queuing(struct kthread_worker *worker,
> +				struct kthread_work *work);
> +void kthread_unblock_work_queuing(struct kthread_worker *worker,
> +				  struct kthread_work *work);
>   
>   void kthread_destroy_worker(struct kthread_worker *worker);
>   
> +/**
> + * kthread_work_queuable - whether or not a kthread work can be queued
> + * @work: The kthread work to check
> + *
> + * Checks whether or not queuing @work is currently blocked from queuing,
> + * either by kthread_cancel_work_sync() and friends or
> + * kthread_block_work_queuing().
> + *
> + * Returns: whether or not the @work may be queued.
> + */
> +static inline bool kthread_work_queuable(struct kthread_work *work)
> +{
> +	return READ_ONCE(work->canceling) == 0;
> +}
> +
>   struct cgroup_subsys_state;
>   
>   #ifdef CONFIG_BLK_CGROUP
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index c1f8ec9d5836..f8a5c5a87cc6 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -1187,6 +1187,52 @@ bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
>   }
>   EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);
>   
> +/**
> + * kthread_block_work_queuing - prevent a kthread_work from being queued
> + * without actually cancelling it
> + * @worker: kthread worker to use
> + * @work: work to block queuing on
> + *
> + * Prevents @work from being queued using kthread_queue_work() and friends,
> + * but doesn't attempt to cancel any previous queuing. The caller must unblock
> + * queuing later by calling kthread_unblock_work_queuing(). This call can be
> + * called multiple times.
> + *
> + * See also: kthread_work_queuable()
> + */
> +void kthread_block_work_queuing(struct kthread_worker *worker,
> +				struct kthread_work *work)
> +{
> +	unsigned long flags;
> +
> +	raw_spin_lock_irqsave(&worker->lock, flags);
> +	work->canceling++;
> +	raw_spin_unlock_irqrestore(&worker->lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(kthread_block_work_queuing);
> +
> +/**
> + * kthread_unblock_work_queuing - unblock queuing on a kthread_work
> + * @worker: kthread worker to use
> + * @work: work to unblock queuing on
> + *
> + * Removes a request to prevent @work from being queued with
> + * kthread_queue_work() and friends, so that it may potentially be queued
> + * again.
> + *
> + * See also: kthread_work_queuable()
> + */
> +void kthread_unblock_work_queuing(struct kthread_worker *worker,
> +				  struct kthread_work *work)
> +{
> +	unsigned long flags;
> +
> +	raw_spin_lock_irqsave(&worker->lock, flags);
> +	WARN_ON_ONCE(--work->canceling < 0);
> +	raw_spin_unlock_irqrestore(&worker->lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(kthread_unblock_work_queuing);
> +
>   /**
>    * kthread_flush_worker - flush all current works on a kthread_worker
>    * @worker: worker to flush