linux-kernel - [PATCH v2 2/3] media: vimc: Serialize vimc_streamer_s

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Date:   Fri, 24 Jul 2020 17:32:12 +0530
From:   Kaaira Gupta <kgupta@...iitr.ac.in>
To:     Helen Koike <helen.koike@...labora.com>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kieran Bingham <kieran.bingham@...asonboard.com>,
        Niklas Söderlund <niklas.soderlund@...natech.se>
Cc:     Kaaira Gupta <kgupta@...iitr.ac.in>
Subject: [PATCH v2 2/3] media: vimc: Serialize vimc_streamer_s_stream()

Prepare for multiple video streams from the same sensor by serializing
vimc_streamer_s_stream(). Multiple streams will allow for multiple
concurrent calls to this function that could involve the same
subdevices.

If that happens the internal state of the involved subdevices could go
out of sync as they are being started and stopped at the same time,
prevent this by serializing starting and stopping of the vimc streamer.

[Kaaira: rebased the patch on current HEAD of media-tree
(8f2a4a9d5ff5202d0b3e3a144ebb9b67aabadd29)]

Signed-off-by: Niklas Söderlund <niklas.soderlund@...natech.se>
Signed-off-by: Kaaira Gupta <kgupta@...iitr.ac.in>
---
 .../media/test-drivers/vimc/vimc-streamer.c   | 23 ++++++++++++-------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/media/test-drivers/vimc/vimc-streamer.c b/drivers/media/test-drivers/vimc/vimc-streamer.c
index 451a32c0d034..5cd2f86a146a 100644
--- a/drivers/media/test-drivers/vimc/vimc-streamer.c
+++ b/drivers/media/test-drivers/vimc/vimc-streamer.c
@@ -192,18 +192,23 @@ int vimc_streamer_s_stream(struct vimc_stream *stream,
 			   struct vimc_ent_device *ved,
 			   int enable)
 {
+	static DEFINE_MUTEX(vimc_streamer_lock);
 	int ret;
 
 	if (!stream || !ved)
 		return -EINVAL;
 
+	ret = mutex_lock_interruptible(&vimc_streamer_lock);
+	if (ret)
+		return ret;
+
 	if (enable) {
 		if (stream->kthread)
-			return 0;
+			goto out;
 
 		ret = vimc_streamer_pipeline_init(stream, ved);
 		if (ret)
-			return ret;
+			goto out;
 
 		stream->kthread = kthread_run(vimc_streamer_thread, stream,
 					      "vimc-streamer thread");
@@ -211,14 +216,12 @@ int vimc_streamer_s_stream(struct vimc_stream *stream,
 		if (IS_ERR(stream->kthread)) {
 			ret = PTR_ERR(stream->kthread);
 			dev_err(ved->dev, "kthread_run failed with %d\n", ret);
-			vimc_streamer_pipeline_terminate(stream);
-			stream->kthread = NULL;
-			return ret;
+			goto out;
 		}
 
 	} else {
 		if (!stream->kthread)
-			return 0;
+			goto out;
 
 		ret = kthread_stop(stream->kthread);
 		/*
@@ -227,13 +230,17 @@ int vimc_streamer_s_stream(struct vimc_stream *stream,
 		 * a chance to run. Ignore errors to stop the stream in the
 		 * pipeline.
 		 */
-		if (ret)
+		if (ret) {
 			dev_dbg(ved->dev, "kthread_stop returned '%d'\n", ret);
+			goto out;
+		}
 
 		stream->kthread = NULL;
 
 		vimc_streamer_pipeline_terminate(stream);
 	}
+out:
+	mutex_unlock(&vimc_streamer_lock);
 
-	return 0;
+	return ret;
 }
-- 
2.17.1