From c599e85c50858d57de92ba4316011ea3872b95a3 Mon Sep 17 00:00:00 2001
From: Tim Blechmann <tim@klingt.org>
Date: Wed, 24 Apr 2024 13:45:25 +0800
Subject: GStreamer: QGstreamerImageCapture - add mutex
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`probeBuffer` and `saveBufferToImage` are called from gstreamer threads.
We therefore need to guard all members with a mutex that are accessed
from both the owning thread and the gstreamer thread.

Pick-to: 6.5 6.7
Change-Id: If9ba7fd761c7756b1eb8cc83f757a80c6a4cac8e
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
---
 .../gstreamer/mediacapture/qgstreamerimagecapture.cpp     | 15 +++++++++++++--
 .../gstreamer/mediacapture/qgstreamerimagecapture_p.h     |  3 +++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamerimagecapture.cpp b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamerimagecapture.cpp
index 5ef797d6e..2f8a1d776 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamerimagecapture.cpp
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamerimagecapture.cpp
@@ -81,6 +81,7 @@ QGstreamerImageCapture::~QGstreamerImageCapture()
 
 bool QGstreamerImageCapture::isReadyForCapture() const
 {
+    QMutexLocker guard(&m_mutex);
     return m_session && !passImage && cameraActive;
 }
 
@@ -107,6 +108,7 @@ int QGstreamerImageCapture::doCapture(const QString &fileName)
         QMetaObject::invokeMethod(this, std::forward<decltype(fn)>(fn), Qt::QueuedConnection);
     };
 
+    QMutexLocker guard(&m_mutex);
     if (!m_session) {
         invokeDeferred([this] {
             emit error(-1, QImageCapture::ResourceError,
@@ -161,6 +163,8 @@ void QGstreamerImageCapture::setResolution(const QSize &resolution)
 
 bool QGstreamerImageCapture::probeBuffer(GstBuffer *buffer)
 {
+    QMutexLocker guard(&m_mutex);
+
     if (!passImage)
         return false;
     qCDebug(qLcImageCaptureGst) << "probe buffer";
@@ -214,6 +218,7 @@ bool QGstreamerImageCapture::probeBuffer(GstBuffer *buffer)
 
 void QGstreamerImageCapture::setCaptureSession(QPlatformMediaCaptureSession *session)
 {
+    QMutexLocker guard(&m_mutex);
     QGstreamerMediaCapture *captureSession = static_cast<QGstreamerMediaCapture *>(session);
     if (m_session == captureSession)
         return;
@@ -241,7 +246,10 @@ void QGstreamerImageCapture::setCaptureSession(QPlatformMediaCaptureSession *ses
 
 void QGstreamerImageCapture::setMetaData(const QMediaMetaData &m)
 {
-    QPlatformImageCapture::setMetaData(m);
+    {
+        QMutexLocker guard(&m_mutex);
+        QPlatformImageCapture::setMetaData(m);
+    }
 
     // ensure taginject injects this metaData
     applyMetaDataToTagSetter(m, muxer);
@@ -259,9 +267,11 @@ void QGstreamerImageCapture::cameraActiveChanged(bool active)
 
 void QGstreamerImageCapture::onCameraChanged()
 {
+    QMutexLocker guard(&m_mutex);
     if (m_session->camera()) {
         cameraActiveChanged(m_session->camera()->isActive());
-        connect(m_session->camera(), &QPlatformCamera::activeChanged, this, &QGstreamerImageCapture::cameraActiveChanged);
+        connect(m_session->camera(), &QPlatformCamera::activeChanged, this,
+                &QGstreamerImageCapture::cameraActiveChanged);
     } else {
         cameraActiveChanged(false);
     }
@@ -276,6 +286,7 @@ gboolean QGstreamerImageCapture::saveImageFilter(GstElement *, GstBuffer *buffer
 
 void QGstreamerImageCapture::saveBufferToImage(GstBuffer *buffer)
 {
+    QMutexLocker guard(&m_mutex);
     passImage = false;
 
     if (pendingImages.isEmpty())
diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamerimagecapture_p.h b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamerimagecapture_p.h
index 7be44a239..4b2220d12 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamerimagecapture_p.h
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamerimagecapture_p.h
@@ -18,6 +18,7 @@
 #include <QtMultimedia/private/qplatformimagecapture_p.h>
 #include <QtMultimedia/private/qmultimediautils_p.h>
 
+#include <QtCore/qmutex.h>
 #include <QtCore/qqueue.h>
 
 #include <common/qgst_p.h>
@@ -65,6 +66,8 @@ private:
 
     void saveBufferToImage(GstBuffer *buffer);
 
+    mutable QRecursiveMutex
+            m_mutex; // guard all elements accessed from probeBuffer/saveBufferToImage
     QGstreamerMediaCapture *m_session = nullptr;
     int m_lastId = 0;
     QImageEncoderSettings m_settings;
-- 
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