Re: [PATCHv3] media: venus: provide video device lock

[Sergey Senozhatsky <senozhatsky@chromium.org>]

On (23/05/24 22:06), Vikash Garodia wrote:
> > Instead the struct v4l2_m2m_ctx q_lock pointer, if set, will use that
> > mutex for all vb2 operations.
> > 
> > I think you can set it to the 'lock' mutex in struct venus_inst.
> 
> IIUC, the suggestion is to use the 'lock' in struct venus_inst while
> initializing the queue. This might lead to deadlock as the same lock is used
> during vb2 operations in driver. Might be introducing a new lock for this
> purpose in struct venus_inst would do, unless we are trying to serialize at
> video device (or core) context.

Something like this?

Video device has to provide a lock so that __video_do_ioctl()
can serialize IOCTL calls. Introduce a dedicated venus_inst
mutex (which is set a ctx ->q_lock) for the purpose of vb2
operations synchronization.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 drivers/media/platform/qcom/venus/core.h | 2 ++
 drivers/media/platform/qcom/venus/vdec.c | 4 ++++
 drivers/media/platform/qcom/venus/venc.c | 3 +++
 3 files changed, 9 insertions(+)

diff --git a/drivers/media/platform/qcom/venus/core.h b/drivers/media/platform/qcom/venus/core.h
index 4f81669986ba..6ac5236d6888 100644
--- a/drivers/media/platform/qcom/venus/core.h
+++ b/drivers/media/platform/qcom/venus/core.h
@@ -389,6 +389,7 @@ enum venus_inst_modes {
  * @sequence_out:	a sequence counter for output queue
  * @m2m_dev:	a reference to m2m device structure
  * @m2m_ctx:	a reference to m2m context structure
+ * @ctx_queue_lock:	a lock to serialize video device ioctl calls
  * @state:	current state of the instance
  * @done:	a completion for sync HFI operation
  * @error:	an error returned during last HFI sync operation
@@ -460,6 +461,7 @@ struct venus_inst {
 	u32 sequence_out;
 	struct v4l2_m2m_dev *m2m_dev;
 	struct v4l2_m2m_ctx *m2m_ctx;
+	struct mutex ctx_queue_lock;
 	unsigned int state;
 	struct completion done;
 	unsigned int error;
diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
index 51a53bf82bd3..2caeba5b6378 100644
--- a/drivers/media/platform/qcom/venus/vdec.c
+++ b/drivers/media/platform/qcom/venus/vdec.c
@@ -1641,6 +1641,7 @@ static int vdec_open(struct file *file)
 	INIT_LIST_HEAD(&inst->internalbufs);
 	INIT_LIST_HEAD(&inst->list);
 	mutex_init(&inst->lock);
+	mutex_init(&inst->ctx_queue_lock);
 
 	inst->core = core;
 	inst->session_type = VIDC_SESSION_TYPE_DEC;
@@ -1684,8 +1685,10 @@ static int vdec_open(struct file *file)
 		goto err_m2m_release;
 	}
 
+
 	v4l2_fh_init(&inst->fh, core->vdev_dec);
 
+	inst->m2m_ctx->q_lock = &inst->ctx_queue_lock;
 	inst->fh.ctrl_handler = &inst->ctrl_handler;
 	v4l2_fh_add(&inst->fh);
 	inst->fh.m2m_ctx = inst->m2m_ctx;
@@ -1716,6 +1719,7 @@ static int vdec_close(struct file *file)
 	ida_destroy(&inst->dpb_ids);
 	hfi_session_destroy(inst);
 	mutex_destroy(&inst->lock);
+	mutex_destroy(&inst->ctx_queue_lock);
 	v4l2_fh_del(&inst->fh);
 	v4l2_fh_exit(&inst->fh);
 
diff --git a/drivers/media/platform/qcom/venus/venc.c b/drivers/media/platform/qcom/venus/venc.c
index 4666f42feea3..4292b299f014 100644
--- a/drivers/media/platform/qcom/venus/venc.c
+++ b/drivers/media/platform/qcom/venus/venc.c
@@ -1443,6 +1443,7 @@ static int venc_open(struct file *file)
 	INIT_LIST_HEAD(&inst->internalbufs);
 	INIT_LIST_HEAD(&inst->list);
 	mutex_init(&inst->lock);
+	mutex_init(&inst->ctx_queue_lock);
 
 	inst->core = core;
 	inst->session_type = VIDC_SESSION_TYPE_ENC;
@@ -1483,6 +1484,7 @@ static int venc_open(struct file *file)
 
 	v4l2_fh_init(&inst->fh, core->vdev_enc);
 
+	inst->m2m_ctx->q_lock = &inst->ctx_queue_lock;
 	inst->fh.ctrl_handler = &inst->ctrl_handler;
 	v4l2_fh_add(&inst->fh);
 	inst->fh.m2m_ctx = inst->m2m_ctx;
@@ -1512,6 +1514,7 @@ static int venc_close(struct file *file)
 	venc_ctrl_deinit(inst);
 	hfi_session_destroy(inst);
 	mutex_destroy(&inst->lock);
+	mutex_destroy(&inst->ctx_queue_lock);
 	v4l2_fh_del(&inst->fh);
 	v4l2_fh_exit(&inst->fh);
 
-- 
2.40.1.698.g37aff9b760-goog