[PATCH v1 1/9] media: chips-media: wave5: Ensure Atomic Access to src_buf list

[Jackson.lee]

From: Brandon Brnich <b-brnich@xxxxxx>

feed_lock was introduced in decoder performance improvements. This was
used to ensure atomic access to the driver's avail_src_buf list during
fill_ringbuffer, streamoff_output, and buf_queue. While this protected
the drivers available src bufs, the v4l2_m2m_src_bufs were not being
protected at driver level. Three separate threads have access to remove
buffers: start_decode fail path, streamoff_output, and finish_decode.

In streamoff_output(), replace the inst_src_buf_remove() loop with
list_for_each_entry_safe(). inst_src_buf_remove() takes feed_lock
itself, so calling it while streamoff_output() holds feed_lock would
take the same mutex twice and deadlock. Unlink each entry with
list_del_init() directly instead.

Fixes: a176ac5e701f ("media: chips-media: wave5: Improve performance of decoder")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Brandon Brnich <b-brnich@xxxxxx>
Signed-off-by: Jackson Lee <jackson.lee@xxxxxxxxxxxxxxx>
Signed-off-by: Nas Chung <nas.chung@xxxxxxxxxxxxxxx>
---
 .../media/platform/chips-media/wave5/wave5-vpu-dec.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c b/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c
index 6564cf3ec739..6af7d2e9a9f3 100644
--- a/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c
+++ b/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c
@@ -198,6 +198,7 @@ static void wave5_handle_src_buffer(struct vpu_instance *inst, dma_addr_t rd_ptr
 	dev_dbg(inst->dev->dev, "%s: %zu bytes of bitstream was consumed", __func__,
 		consumed_bytes);
 
+	mutex_lock(&inst->feed_lock);
 	v4l2_m2m_for_each_src_buf_safe(m2m_ctx, buf, n) {
 		struct vb2_v4l2_buffer *src_buf = &buf->vb;
 		size_t src_size = vb2_get_plane_payload(&src_buf->vb2_buf, 0);
@@ -224,6 +225,7 @@ static void wave5_handle_src_buffer(struct vpu_instance *inst, dma_addr_t rd_ptr
 			break;
 		}
 	}
+	mutex_unlock(&inst->feed_lock);
 
 	inst->remaining_consumed_bytes = consumed_bytes;
 }
@@ -237,9 +239,11 @@ static int start_decode(struct vpu_instance *inst, u32 *fail_res)
 	if (ret) {
 		struct vb2_v4l2_buffer *src_buf;
 
+		mutex_lock(&inst->feed_lock);
 		src_buf = v4l2_m2m_src_buf_remove(m2m_ctx);
 		if (src_buf)
 			v4l2_m2m_buf_done(src_buf, VB2_BUF_STATE_ERROR);
+		mutex_unlock(&inst->feed_lock);
 		set_instance_state(inst, VPU_INST_STATE_STOP);
 
 		dev_dbg(inst->dev->dev, "%s: pic run failed / finish job", __func__);
@@ -1453,12 +1457,13 @@ static int streamoff_output(struct vb2_queue *q)
 	dma_addr_t new_rd_ptr;
 	struct dec_output_info dec_info;
 	unsigned int i;
-	struct vpu_src_buffer *vpu_buf;
+	struct vpu_src_buffer *vpu_buf, *tmp;
 
 	inst->retry = false;
 	inst->queuing_num = 0;
-	while ((vpu_buf = inst_src_buf_remove(inst)) != NULL)
-		;
+	mutex_lock(&inst->feed_lock);
+	list_for_each_entry_safe(vpu_buf, tmp, &inst->avail_src_bufs, list)
+		list_del_init(&vpu_buf->list);
 
 	for (i = 0; i < v4l2_m2m_num_dst_bufs_ready(m2m_ctx); i++) {
 		ret = wave5_vpu_dec_set_disp_flag(inst, i);
@@ -1473,6 +1478,7 @@ static int streamoff_output(struct vb2_queue *q)
 			__func__, buf->vb2_buf.type, buf->vb2_buf.index);
 		v4l2_m2m_buf_done(buf, VB2_BUF_STATE_ERROR);
 	}
+	mutex_unlock(&inst->feed_lock);
 
 	while (wave5_vpu_dec_get_output_info(inst, &dec_info) == 0) {
 		if (dec_info.index_frame_display >= 0)
-- 
2.43.0