Message-ID: <a23922e98926f14158d1cb8525026d7cdfea7b52.camel@collabora.com>
Date: Mon, 15 Sep 2025 16:14:18 -0400
From: Nicolas Dufresne <nicolas.dufresne@...labora.com>
To: "jackson.lee" <jackson.lee@...psnmedia.com>, "mchehab@...nel.org"	
 <mchehab@...nel.org>, "hverkuil-cisco@...all.nl"
 <hverkuil-cisco@...all.nl>,  "bob.beckett@...labora.com"	
 <bob.beckett@...labora.com>
Cc: "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>, 
 "linux-kernel@...r.kernel.org"	 <linux-kernel@...r.kernel.org>,
 "lafley.kim" <lafley.kim@...psnmedia.com>,  "b-brnich@...com"	
 <b-brnich@...com>, "hverkuil@...all.nl" <hverkuil@...all.nl>, Nas Chung	
 <nas.chung@...psnmedia.com>
Subject: Re: [PATCH v3 0/4] Performance improvement of decoder

Le lundi 15 septembre 2025 à 07:33 +0000, jackson.lee a écrit :
> Hi Nicolas
> 
> > Good catch, unfortunately it does not completely fix the problem for me.
> > You can find a the end of this message the patch I actually tested. Note
> > I ,ove the mutex_ret in a close scope, and fixed other occurence of this
> > pattern, except one that I highlighted to you with a FIXME.
> > 
> > Some new information, I had this trace from GStreamer when the bug occured
> > on forward seeks (very rare):
> > 
> > ** (gst-play-1.0:604): WARNING **: 00:03:59.965: v4l2h264dec0: Too old
> > frames, bug in decoder -- please file a bug
> > 
> > [root@...into nicolas]# echo w > /proc/sysrq-trigger [  335.116289] sysrq:
> > Show Blocked State
> > [  335.120054] task:typefind:sink   state:D stack:0     pid:607   tgid:604
> > ppid:543    task_flags:0x40044c flags:0x00000019
> > [  335.131147] Call trace:
> > [  335.133584]  __switch_to+0xf0/0x1c0 (T) [  335.137442]
> > __schedule+0x35c/0x9bc [  335.140935]  schedule+0x34/0x110 [  335.144162]
> > schedule_timeout+0x80/0x104 [  335.148081]
> > wait_for_completion_timeout+0x74/0x158
> > [  335.152955]  wave5_vpu_wait_interrupt+0x28/0x60 [wave5] [  335.158252]
> > wave5_vpu_dec_stop_streaming+0x68/0x28c [wave5] [  335.163915]
> > __vb2_queue_cancel+0x2c/0x2d4 [videobuf2_common] [  335.169668]
> > vb2_core_queue_release+0x20/0x74 [videobuf2_common] [  335.175678]
> > vb2_queue_release+0x10/0x1c [videobuf2_v4l2] [  335.181081]
> > v4l2_m2m_ctx_release+0x20/0x40 [v4l2_mem2mem] [  335.186567]
> > wave5_vpu_release_device+0x44/0x150 [wave5] [  335.191879]
> > wave5_vpu_dec_release+0x20/0x2c [wave5] [  335.196841]
> > v4l2_release+0xb4/0xf0 [videodev] [  335.201709]  __fput+0xd0/0x2e0
> > [  335.205090]  ____fput+0x14/0x20 [  335.208468]  task_work_run+0x64/0xd4
> > [  335.212164]  do_exit+0x240/0x8e0 [  335.215552]  do_group_exit+0x30/0xa4
> > [  335.219177]  get_signal+0x790/0x860 [  335.222676]  do_signal+0x94/0x394
> > [  335.225986]  do_notify_resume+0xd0/0x14c [  335.229910]
> > el0_svc+0xe4/0xe8 [  335.232967]  el0t_64_sync_handler+0xa0/0xe4
> > [  335.237154]  el0t_64_sync+0x198/0x19c
> > 
> > regards,
> > Nicolas
> > 
> 
> 
> There were two problems.
> 
> One is a logic double linked list managing, it caused crash.
> I added linked list(avail_src_bufs) to manage buffer list queued in order to improve performance of decoder.
> But when it was deleted from list, the prev and next pointer had the previous pointer address, so sometimes it caused crash and deadlock.
> 
> Second, when stop_call function was called, sometimes infinite loop was put. But it is needed since flush was added into streamoff_output.
> 
> To fix the above problems (deadlock and crash), the below patch is needed.
> 
> 
> 
> 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 4554a24df8a1..9572573ce606 100644
> --- a/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c
> +++ b/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c
> @@ -1139,6 +1139,24 @@ static int write_to_ringbuffer(struct vpu_instance *inst, void *buffer, size_t b
>  	return 0;
>  }
>  
> +static struct vpu_src_buffer *inst_buf_remove(struct vpu_instance *inst)
> +{
> +	struct vpu_src_buffer *b;
> +
> +	if (list_empty(&inst->avail_src_bufs))
> +		return NULL;
> +	inst->queued_count--;
> +	b = list_first_entry(&inst->avail_src_bufs, struct vpu_src_buffer, list);
> +	list_del(&b->list);
> +	b->list.prev = b->list.next = NULL;
> +	INIT_LIST_HEAD(&b->list);
> +	if (inst->queued_count == 0) {
> +		inst->avail_src_bufs.prev = inst->avail_src_bufs.next = NULL;
> +		INIT_LIST_HEAD(&inst->avail_src_bufs);
> +	}
> +	return b;
> +}
> +
>  static int fill_ringbuffer(struct vpu_instance *inst)
>  {
>  	struct v4l2_m2m_ctx *m2m_ctx = inst->v4l2_fh.m2m_ctx;
> @@ -1154,7 +1172,7 @@ static int fill_ringbuffer(struct vpu_instance *inst)
>  		}
>  	}
>  
> -	list_for_each_entry(vpu_buf, &inst->avail_src_bufs, list) {
> +	while((vpu_buf = inst_buf_remove(inst)) != NULL) {

Can't you make sure of list_for_each_safe() ?

Nicolas


>  		struct vb2_v4l2_buffer *vbuf = &vpu_buf->v4l2_m2m_buf.vb;
>  		struct vpu_buf *ring_buffer = &inst->bitstream_vbuf;
>  		size_t src_size = vb2_get_plane_payload(&vbuf->vb2_buf, 0);
> @@ -1217,7 +1235,6 @@ static int fill_ringbuffer(struct vpu_instance *inst)
>  		}
>  
>  		inst->queuing_num++;
> -		list_del_init(&vpu_buf->list);
>  		break;
>  	}
>  
> @@ -1233,13 +1250,9 @@ static void wave5_vpu_dec_buf_queue_src(struct vb2_buffer *vb)
>  
>  	vpu_buf->consumed = false;
>  	vbuf->sequence = inst->queued_src_buf_num++;
> -
> -	v4l2_m2m_buf_queue(m2m_ctx, vbuf);
> -
> -	INIT_LIST_HEAD(&vpu_buf->list);
> -	mutex_lock(&inst->feed_lock);
>  	list_add_tail(&vpu_buf->list, &inst->avail_src_bufs);
> -	mutex_unlock(&inst->feed_lock);
> +	inst->queued_count++;
> +	v4l2_m2m_buf_queue(m2m_ctx, vbuf);
>  }
>  
>  static void wave5_vpu_dec_buf_queue_dst(struct vb2_buffer *vb)
> @@ -1292,9 +1305,12 @@ static void wave5_vpu_dec_buf_queue(struct vb2_buffer *vb)
>  		vb2_plane_size(&vbuf->vb2_buf, 1), vb2_plane_size(&vbuf->vb2_buf, 2));
>  
>  	if (vb->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE) {
> +		mutex_lock(&inst->feed_lock);
> +		wave5_vpu_dec_buf_queue_src(vb);
> +
>  		if (inst->empty_queue)
>  			inst->empty_queue = false;
> -		wave5_vpu_dec_buf_queue_src(vb);
> +		mutex_unlock(&inst->feed_lock);
>  	} else if (vb->type == V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE) {
>  		wave5_vpu_dec_buf_queue_dst(vb);
>  	}
> @@ -1396,9 +1412,13 @@ static int streamoff_output(struct vb2_queue *q)
>  
>  	inst->retry = false;
>  	inst->queuing_num = 0;
> -
> -	list_for_each_entry_safe(vpu_buf, tmp, &inst->avail_src_bufs, list)
> -		list_del_init(&vpu_buf->list);
> +	inst->queued_count = 0;
> +	mutex_lock(&inst->feed_lock);
> +	list_for_each_entry_safe(vpu_buf, tmp, &inst->avail_src_bufs, list) {
> +		vpu_buf->consumed = false;
> +		list_del(&vpu_buf->list);
> +	}
> +	mutex_unlock(&inst->feed_lock);
>  
>  	for (i = 0; i < v4l2_m2m_num_dst_bufs_ready(m2m_ctx); i++) {
>  		ret = wave5_vpu_dec_set_disp_flag(inst, i);
> @@ -1484,28 +1504,9 @@ static void wave5_vpu_dec_stop_streaming(struct vb2_queue *q)
>  {
>  	struct vpu_instance *inst = vb2_get_drv_priv(q);
>  	struct v4l2_m2m_ctx *m2m_ctx = inst->v4l2_fh.m2m_ctx;
> -	bool check_cmd = TRUE;
>  
>  	dev_dbg(inst->dev->dev, "%s: type: %u\n", __func__, q->type);
>  	pm_runtime_resume_and_get(inst->dev->dev);
> -	inst->empty_queue = false;
> -	inst->sent_eos = false;
> -
> -	while (check_cmd) {
> -		struct queue_status_info q_status;
> -		struct dec_output_info dec_output_info;
> -
> -		wave5_vpu_dec_give_command(inst, DEC_GET_QUEUE_STATUS, &q_status);
> -
> -		if ((inst->state == VPU_INST_STATE_STOP || q_status.instance_queue_count == 0) &&
> -		    q_status.report_queue_count == 0)
> -			break;
> -
> -		wave5_vpu_wait_interrupt(inst, VPU_DEC_STOP_TIMEOUT);
> -
> -		if (wave5_vpu_dec_get_output_info(inst, &dec_output_info))
> -			dev_dbg(inst->dev->dev, "there is no output info\n");
> -	}
>  
>  	v4l2_m2m_update_stop_streaming_state(m2m_ctx, q);
>  
> @@ -1514,6 +1515,8 @@ static void wave5_vpu_dec_stop_streaming(struct vb2_queue *q)
>  	else
>  		streamoff_capture(q);
>  
> +	inst->empty_queue = false;
> +	inst->sent_eos = false;
>  	pm_runtime_mark_last_busy(inst->dev->dev);
>  	pm_runtime_put_autosuspend(inst->dev->dev);
>  }
> diff --git a/drivers/media/platform/chips-media/wave5/wave5-vpu.h b/drivers/media/platform/chips-media/wave5/wave5-vpu.h
> index 3847332551fc..2e7a6b0bf74a 100644
> --- a/drivers/media/platform/chips-media/wave5/wave5-vpu.h
> +++ b/drivers/media/platform/chips-media/wave5/wave5-vpu.h
> @@ -22,8 +22,8 @@
>  
>  struct vpu_src_buffer {
>  	struct v4l2_m2m_buffer	v4l2_m2m_buf;
> -	struct list_head	list;
>  	bool			consumed;
> +	struct list_head	list;
>  };
>  
>  struct vpu_dst_buffer {
> 
> diff --git a/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c b/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
> index edbe69540ef1..fb41890fc9c1 100644
> --- a/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
> +++ b/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
> @@ -52,11 +52,12 @@ int wave5_vpu_init_with_bitcode(struct device *dev, u8 *bitcode, size_t size)
>  int wave5_vpu_flush_instance(struct vpu_instance *inst)
>  {
>  	int ret = 0;
> +	int mutex_ret = 0;
>  	int retry = 0;
>  
> -	ret = mutex_lock_interruptible(&inst->dev->hw_lock);
> -	if (ret)
> -		return ret;
> +	mutex_ret = mutex_lock_interruptible(&inst->dev->hw_lock);
> +	if (mutex_ret)
> +		return mutex_ret;
>  	do {
>  		/*
>  		 * Repeat the FLUSH command until the firmware reports that the
> @@ -80,15 +81,16 @@ int wave5_vpu_flush_instance(struct vpu_instance *inst)
>  
>  			mutex_unlock(&inst->dev->hw_lock);
>  			wave5_vpu_dec_get_output_info(inst, &dec_info);
> -			ret = mutex_lock_interruptible(&inst->dev->hw_lock);
> -			if (ret)
> -				return ret;
> +			mutex_ret = mutex_lock_interruptible(&inst->dev->hw_lock);
> +			if (mutex_ret) {
> +				printk("lock fail...... \n");
> +				return mutex_ret;
> +			}
>  			if (dec_info.index_frame_display > 0)
>  				wave5_vpu_dec_set_disp_flag(inst, dec_info.index_frame_display);
>  		}
>  	} while (ret != 0);
>  	mutex_unlock(&inst->dev->hw_lock);
> -
>  	return ret;
>  }
>  
> @@ -208,6 +210,7 @@ int wave5_vpu_dec_close(struct vpu_instance *inst, u32 *fail_res)
>  	struct vpu_device *vpu_dev = inst->dev;
>  	int i;
>  	struct dec_output_info dec_info;
> +	int ret_mutex;
>  
>  	*fail_res = 0;
>  	if (!inst->codec_info)
> @@ -215,10 +218,10 @@ int wave5_vpu_dec_close(struct vpu_instance *inst, u32 *fail_res)
>  
>  	pm_runtime_resume_and_get(inst->dev->dev);
>  
> -	ret = mutex_lock_interruptible(&vpu_dev->hw_lock);
> -	if (ret) {
> +	ret_mutex = mutex_lock_interruptible(&vpu_dev->hw_lock);
> +	if (ret_mutex) {
>  		pm_runtime_put_sync(inst->dev->dev);
> -		return ret;
> +		return ret_mutex;
>  	}
>  
>  	do {
> @@ -243,10 +246,10 @@ int wave5_vpu_dec_close(struct vpu_instance *inst, u32 *fail_res)
>  
>  		mutex_unlock(&vpu_dev->hw_lock);
>  		wave5_vpu_dec_get_output_info(inst, &dec_info);
> -		ret = mutex_lock_interruptible(&vpu_dev->hw_lock);
> -		if (ret) {
> +		ret_mutex = mutex_lock_interruptible(&vpu_dev->hw_lock);
> +		if (ret_mutex) {
>  			pm_runtime_put_sync(inst->dev->dev);
> -			return ret;
> +			return ret_mutex;
>  		}
>  	} while (ret != 0);
>  
> diff --git a/drivers/media/platform/chips-media/wave5/wave5-vpuapi.h b/drivers/media/platform/chips-media/wave5/wave5-vpuapi.h
> index d9da80d64278..10f89f327436 100644
> --- a/drivers/media/platform/chips-media/wave5/wave5-vpuapi.h
> +++ b/drivers/media/platform/chips-media/wave5/wave5-vpuapi.h
> @@ -822,6 +822,7 @@ struct vpu_instance {
>  	bool sent_eos; /* check if EOS is sent to application */
>  	bool retry; /* retry to feed bitstream if failure reason is WAVE5_SYSERR_QUEUEING_FAIL*/
>  	int queuing_num; /* count of bitstream queued */
> +	int queued_count;
>  	struct mutex feed_lock; /* lock for feeding bitstream buffers */
>  	bool empty_queue;
>  	struct vpu_buf bitstream_vbuf;

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