Re: [PATCH 4/5] media: staging: rkisp1: stats: replace locks wq_lock, irq_lock with one lock

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Cc: linux-media@vger.kernel.org, helen.koike@collabora.com,
	ezequiel@collabora.com, hverkuil@xs4all.nl, kernel@collabora.com,
	dafna3@gmail.com, sakari.ailus@linux.intel.com,
	linux-rockchip@lists.infradead.org, mchehab@kernel.org
Subject: Re: [PATCH 4/5] media: staging: rkisp1: stats: replace locks wq_lock, irq_lock with one lock
Date: Thu, 21 May 2020 02:48:10 +0300	[thread overview]
Message-ID: <20200520234810.GD25474@pendragon.ideasonboard.com> (raw)
In-Reply-To: <20200512120522.25960-5-dafna.hirschfeld@collabora.com>

Hi Dafna,

Thank you for the patch.

On Tue, May 12, 2020 at 02:05:21PM +0200, Dafna Hirschfeld wrote:
> This patch removes two locks in the rkisp1_stats struct:
> - The mutex 'wq_lock' that is used to protect the buffers list 'stat'
> - The spin_lock 'irq_lock' that is used to protect the
> variable 'is_streaming'
> 
> It replaces them with one spin_lock 'stats_lock' that protects
> both the buffers list and the 'is_streaming' variable.

You should explain in the commit message why this is needed.

> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
> ---
>  drivers/staging/media/rkisp1/rkisp1-common.h |  5 ++--
>  drivers/staging/media/rkisp1/rkisp1-stats.c  | 27 ++++++++++----------
>  2 files changed, 15 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/staging/media/rkisp1/rkisp1-common.h b/drivers/staging/media/rkisp1/rkisp1-common.h
> index c0ab16c6b3db..c635bb0a7727 100644
> --- a/drivers/staging/media/rkisp1/rkisp1-common.h
> +++ b/drivers/staging/media/rkisp1/rkisp1-common.h
> @@ -178,7 +178,7 @@ struct rkisp1_capture {
>  /*
>   * struct rkisp1_stats - ISP Statistics device
>   *
> - * @irq_lock: buffer queue lock
> + * @stats_lock: locks the buffer list 'stat' and 'is_streaming'
>   * @stat: stats buffer list
>   * @readout_wq: workqueue for statistics information read
>   */
> @@ -186,13 +186,12 @@ struct rkisp1_stats {
>  	struct rkisp1_vdev_node vnode;
>  	struct rkisp1_device *rkisp1;
>  
> -	spinlock_t irq_lock;
> +	spinlock_t stats_lock; /* locks 'is_streaming', and 'stats' */

If there's a single lock, how about simply calling it 'lock' ?

>  	struct list_head stat;
>  	struct v4l2_format vdev_fmt;
>  	bool is_streaming;
>  
>  	struct workqueue_struct *readout_wq;
> -	struct mutex wq_lock;
>  };
>  
>  /*
> diff --git a/drivers/staging/media/rkisp1/rkisp1-stats.c b/drivers/staging/media/rkisp1/rkisp1-stats.c
> index 5578fdeb8a18..e6fb2c5f3b3e 100644
> --- a/drivers/staging/media/rkisp1/rkisp1-stats.c
> +++ b/drivers/staging/media/rkisp1/rkisp1-stats.c
> @@ -130,12 +130,13 @@ static void rkisp1_stats_vb2_buf_queue(struct vb2_buffer *vb)
>  		container_of(vbuf, struct rkisp1_buffer, vb);
>  	struct vb2_queue *vq = vb->vb2_queue;
>  	struct rkisp1_stats *stats_dev = vq->drv_priv;
> +	unsigned long flags;
>  
>  	stats_buf->vaddr[0] = vb2_plane_vaddr(vb, 0);
>  
> -	mutex_lock(&stats_dev->wq_lock);
> +	spin_lock_irqsave(&stats_dev->stats_lock, flags);

As I explained in a previous e-mail in this series, you could use
spin_lock_irq() here as there's a guarantee interrupts are not disabled.
Up to you.

>  	list_add_tail(&stats_buf->queue, &stats_dev->stat);
> -	mutex_unlock(&stats_dev->wq_lock);
> +	spin_unlock_irqrestore(&stats_dev->stats_lock, flags);
>  }
>  
>  static int rkisp1_stats_vb2_buf_prepare(struct vb2_buffer *vb)
> @@ -156,13 +157,13 @@ static void rkisp1_stats_vb2_stop_streaming(struct vb2_queue *vq)
>  	unsigned int i;
>  
>  	/* Make sure no new work queued in isr before draining wq */
> -	spin_lock_irqsave(&stats->irq_lock, flags);
> +	spin_lock_irqsave(&stats->stats_lock, flags);
>  	stats->is_streaming = false;
> -	spin_unlock_irqrestore(&stats->irq_lock, flags);
> +	spin_unlock_irqrestore(&stats->stats_lock, flags);
>  
>  	drain_workqueue(stats->readout_wq);
>  
> -	mutex_lock(&stats->wq_lock);
> +	spin_lock_irqsave(&stats->stats_lock, flags);
>  	for (i = 0; i < RKISP1_ISP_STATS_REQ_BUFS_MAX; i++) {
>  		if (list_empty(&stats->stat))
>  			break;
> @@ -171,7 +172,7 @@ static void rkisp1_stats_vb2_stop_streaming(struct vb2_queue *vq)
>  		list_del(&buf->queue);
>  		vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_ERROR);
>  	}
> -	mutex_unlock(&stats->wq_lock);
> +	spin_unlock_irqrestore(&stats->stats_lock, flags);
>  }
>  
>  static int
> @@ -333,6 +334,7 @@ rkisp1_stats_send_measurement(struct rkisp1_stats *stats,
>  	unsigned int frame_sequence =
>  		atomic_read(&stats->rkisp1->isp.frame_sequence);
>  	u64 timestamp = ktime_get_ns();
> +	unsigned long flags;
>  
>  	if (frame_sequence != meas_work->frame_id) {
>  		dev_warn(stats->rkisp1->dev,
> @@ -341,14 +343,14 @@ rkisp1_stats_send_measurement(struct rkisp1_stats *stats,
>  		frame_sequence = meas_work->frame_id;
>  	}
>  
> -	mutex_lock(&stats->wq_lock);
> +	spin_lock_irqsave(&stats->stats_lock, flags);
>  	/* get one empty buffer */
>  	if (!list_empty(&stats->stat)) {
>  		cur_buf = list_first_entry(&stats->stat,
>  					   struct rkisp1_buffer, queue);
>  		list_del(&cur_buf->queue);
>  	}
> -	mutex_unlock(&stats->wq_lock);
> +	spin_unlock_irqrestore(&stats->stats_lock, flags);
>  
>  	if (!cur_buf)
>  		return;
> @@ -406,7 +408,7 @@ void rkisp1_stats_isr(struct rkisp1_stats *stats, u32 isp_ris)
>  	unsigned long flags;
>  	u32 val;
>  
> -	spin_lock_irqsave(&stats->irq_lock, flags);
> +	spin_lock_irqsave(&stats->stats_lock, flags);
>  
>  	val = RKISP1_STATS_MEAS_MASK;
>  	rkisp1_write(rkisp1, val, RKISP1_CIF_ISP_ICR);
> @@ -436,7 +438,7 @@ void rkisp1_stats_isr(struct rkisp1_stats *stats, u32 isp_ris)
>  	}
>  
>  unlock:
> -	spin_unlock_irqrestore(&stats->irq_lock, flags);
> +	spin_unlock_irqrestore(&stats->stats_lock, flags);
>  }
>  
>  static void rkisp1_init_stats(struct rkisp1_stats *stats)
> @@ -456,10 +458,9 @@ int rkisp1_stats_register(struct rkisp1_stats *stats,
>  	int ret;
>  
>  	stats->rkisp1 = rkisp1;
> -	mutex_init(&stats->wq_lock);
>  	mutex_init(&node->vlock);
>  	INIT_LIST_HEAD(&stats->stat);
> -	spin_lock_init(&stats->irq_lock);
> +	spin_lock_init(&stats->stats_lock);
>  
>  	strscpy(vdev->name, RKISP1_STATS_DEV_NAME, sizeof(vdev->name));
>  
> @@ -506,7 +507,6 @@ int rkisp1_stats_register(struct rkisp1_stats *stats,
>  err_release_queue:
>  	vb2_queue_release(vdev->queue);
>  	mutex_destroy(&node->vlock);
> -	mutex_destroy(&stats->wq_lock);
>  	return ret;
>  }
>  
> @@ -520,5 +520,4 @@ void rkisp1_stats_unregister(struct rkisp1_stats *stats)
>  	media_entity_cleanup(&vdev->entity);
>  	vb2_queue_release(vdev->queue);
>  	mutex_destroy(&node->vlock);
> -	mutex_destroy(&stats->wq_lock);
>  }

-- 
Regards,

Laurent Pinchart