Quoting Laurent Pinchart (2024-05-05 18:45:44)
> The histogram support mixes _irqsave and _irq, causing the following
> smatch warning:
>
> drivers/media/platform/renesas/vsp1/vsp1_histo.c:153 histo_stop_streaming()
> warn: mixing irqsave and irq
>
> The histo_stop_streaming() calls spin_lock_irqsave() followed by
> wait_event_lock_irq(). The former hints that interrupts may be disabled
> by the caller, while the latter reenables interrupts unconditionally.
> This doesn't cause any real bug, as the function is always called with
> interrupts enabled, but the pattern is still in correct.
>
> Fix the problem by using spin_lock_irq() instead of spin_lock_irqsave()
> in histo_stop_streaming(). While at it, switch to spin_lock_irq() and
> spin_lock() as appropriate elsewhere.
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> Fixes: 99362e32332b ("[media] v4l: vsp1: Add histogram support")
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Closes: https://lore.kernel.org/linux-renesas-soc/164d74ff-312c-468f-be64-afa7182cd2f4@moroto.mountain/
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
> ---
> .../media/platform/renesas/vsp1/vsp1_histo.c | 20 ++++++++-----------
> 1 file changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/media/platform/renesas/vsp1/vsp1_histo.c b/drivers/media/platform/renesas/vsp1/vsp1_histo.c
> index 71155282ca11..cd1c8778662e 100644
> --- a/drivers/media/platform/renesas/vsp1/vsp1_histo.c
> +++ b/drivers/media/platform/renesas/vsp1/vsp1_histo.c
> @@ -36,9 +36,8 @@ struct vsp1_histogram_buffer *
> vsp1_histogram_buffer_get(struct vsp1_histogram *histo)
> {
> struct vsp1_histogram_buffer *buf = NULL;
> - unsigned long flags;
>
> - spin_lock_irqsave(&histo->irqlock, flags);
> + spin_lock(&histo->irqlock);
>
> if (list_empty(&histo->irqqueue))
> goto done;
> @@ -49,7 +48,7 @@ vsp1_histogram_buffer_get(struct vsp1_histogram *histo)
> histo->readout = true;
>
> done:
> - spin_unlock_irqrestore(&histo->irqlock, flags);
> + spin_unlock(&histo->irqlock);
> return buf;
> }
>
> @@ -58,7 +57,6 @@ void vsp1_histogram_buffer_complete(struct vsp1_histogram *histo,
> size_t size)
> {
> struct vsp1_pipeline *pipe = histo->entity.pipe;
> - unsigned long flags;
>
> /*
> * The pipeline pointer is guaranteed to be valid as this function is
> @@ -70,10 +68,10 @@ void vsp1_histogram_buffer_complete(struct vsp1_histogram *histo,
> vb2_set_plane_payload(&buf->buf.vb2_buf, 0, size);
> vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_DONE);
>
> - spin_lock_irqsave(&histo->irqlock, flags);
> + spin_lock(&histo->irqlock);
> histo->readout = false;
> wake_up(&histo->wait_queue);
> - spin_unlock_irqrestore(&histo->irqlock, flags);
> + spin_unlock(&histo->irqlock);
> }
>
> /* -----------------------------------------------------------------------------
> @@ -124,11 +122,10 @@ static void histo_buffer_queue(struct vb2_buffer *vb)
> struct vb2_v4l2_buffer *vbuf = to_vb2_v4l2_buffer(vb);
> struct vsp1_histogram *histo = vb2_get_drv_priv(vb->vb2_queue);
> struct vsp1_histogram_buffer *buf = to_vsp1_histogram_buffer(vbuf);
> - unsigned long flags;
>
> - spin_lock_irqsave(&histo->irqlock, flags);
> + spin_lock_irq(&histo->irqlock);
> list_add_tail(&buf->queue, &histo->irqqueue);
> - spin_unlock_irqrestore(&histo->irqlock, flags);
> + spin_unlock_irq(&histo->irqlock);
> }
>
> static int histo_start_streaming(struct vb2_queue *vq, unsigned int count)
> @@ -140,9 +137,8 @@ static void histo_stop_streaming(struct vb2_queue *vq)
> {
> struct vsp1_histogram *histo = vb2_get_drv_priv(vq);
> struct vsp1_histogram_buffer *buffer;
> - unsigned long flags;
>
> - spin_lock_irqsave(&histo->irqlock, flags);
> + spin_lock_irq(&histo->irqlock);
>
> /* Remove all buffers from the IRQ queue. */
> list_for_each_entry(buffer, &histo->irqqueue, queue)
> @@ -152,7 +148,7 @@ static void histo_stop_streaming(struct vb2_queue *vq)
> /* Wait for the buffer being read out (if any) to complete. */
> wait_event_lock_irq(histo->wait_queue, !histo->readout, histo->irqlock);
>
> - spin_unlock_irqrestore(&histo->irqlock, flags);
> + spin_unlock_irq(&histo->irqlock);
> }
>
> static const struct vb2_ops histo_video_queue_qops = {
>
> base-commit: e695668af8523b059127dfa8b261c76e7c9cde10
> --
> Regards,
>
> Laurent Pinchart
>
