From: Jan Grulich <jgrulich@redhat.com>
Date: Tue, 13 Feb 2024 13:12:00 +0000
Subject: Bug 1879752 - WebRTC backport: Video capture PipeWire - simplify
 thread and lock annotations r=pehrsons,webrtc-reviewers

This is a simple backport of an WebRTC upstream change.

Upstream commit: 541f202354e2b4906935c8db6e54386aa8bc8d1f

Differential Revision: https://phabricator.services.mozilla.com/D201328
Mercurial Revision: https://hg.mozilla.org/mozilla-central/rev/dc12e6eecaa8dc91ee0a517cfd27570691c441b9
---
 .../linux/video_capture_pipewire.cc           | 25 ++++++++++++-------
 .../linux/video_capture_pipewire.h            | 14 +++++------
 2 files changed, 22 insertions(+), 17 deletions(-)

diff --git a/modules/video_capture/linux/video_capture_pipewire.cc b/modules/video_capture/linux/video_capture_pipewire.cc
index fb813e331f..8af483636a 100644
--- a/modules/video_capture/linux/video_capture_pipewire.cc
+++ b/modules/video_capture/linux/video_capture_pipewire.cc
@@ -121,7 +121,6 @@ static spa_pod* BuildFormat(spa_pod_builder* builder,
 
 int32_t VideoCaptureModulePipeWire::StartCapture(
     const VideoCaptureCapability& capability) {
-  RTC_CHECK_RUNS_SERIALIZED(&capture_checker_);
   RTC_DCHECK_RUN_ON(&api_checker_);
 
   if (initialized_) {
@@ -134,10 +133,17 @@ int32_t VideoCaptureModulePipeWire::StartCapture(
 
   uint8_t buffer[1024] = {};
 
+  // We don't want members above to be guarded by capture_checker_ as
+  // it's meant to be for members that are accessed on the API thread
+  // only when we are not capturing. The code above can be called many
+  // times while sharing instance of VideoCapturePipeWire between
+  // websites and therefore it would not follow the requirements of this
+  // checker.
+  RTC_CHECK_RUNS_SERIALIZED(&capture_checker_);
+  PipeWireThreadLoopLock thread_loop_lock(session_->pw_main_loop_);
+
   RTC_LOG(LS_VERBOSE) << "Creating new PipeWire stream for node " << node_id_;
 
-  PipeWireThreadLoopLock thread_loop_lock(session_->pw_main_loop_);
-  RTC_CHECK_RUNS_SERIALIZED(&pipewire_checker_);
   pw_properties* reuse_props =
       pw_properties_new_string("pipewire.client.reuse=1");
   stream_ = pw_stream_new(session_->pw_core_, "camera-stream", reuse_props);
@@ -188,11 +194,13 @@ int32_t VideoCaptureModulePipeWire::StartCapture(
 }
 
 int32_t VideoCaptureModulePipeWire::StopCapture() {
-  RTC_CHECK_RUNS_SERIALIZED(&capture_checker_);
   RTC_DCHECK_RUN_ON(&api_checker_);
 
   PipeWireThreadLoopLock thread_loop_lock(session_->pw_main_loop_);
-  RTC_CHECK_RUNS_SERIALIZED(&pipewire_checker_);
+  // PipeWireSession is guarded by API checker so just make sure we do
+  // race detection when the PipeWire loop is locked/stopped to not run
+  // any callback at this point.
+  RTC_CHECK_RUNS_SERIALIZED(&capture_checker_);
   if (stream_) {
     pw_stream_destroy(stream_);
     stream_ = nullptr;
@@ -225,14 +233,14 @@ void VideoCaptureModulePipeWire::OnStreamParamChanged(
   VideoCaptureModulePipeWire* that =
       static_cast<VideoCaptureModulePipeWire*>(data);
   RTC_DCHECK(that);
-  RTC_CHECK_RUNS_SERIALIZED(&that->pipewire_checker_);
+  RTC_CHECK_RUNS_SERIALIZED(&that->capture_checker_);
 
   if (format && id == SPA_PARAM_Format)
     that->OnFormatChanged(format);
 }
 
 void VideoCaptureModulePipeWire::OnFormatChanged(const struct spa_pod* format) {
-  RTC_CHECK_RUNS_SERIALIZED(&pipewire_checker_);
+  RTC_CHECK_RUNS_SERIALIZED(&capture_checker_);
 
   uint32_t media_type, media_subtype;
 
@@ -331,7 +339,6 @@ void VideoCaptureModulePipeWire::OnStreamStateChanged(
   VideoCaptureModulePipeWire* that =
       static_cast<VideoCaptureModulePipeWire*>(data);
   RTC_DCHECK(that);
-  RTC_CHECK_RUNS_SERIALIZED(&that->capture_checker_);
 
   MutexLock lock(&that->api_lock_);
   switch (state) {
@@ -374,7 +381,7 @@ static VideoRotation VideorotationFromPipeWireTransform(uint32_t transform) {
 }
 
 void VideoCaptureModulePipeWire::ProcessBuffers() {
-  RTC_CHECK_RUNS_SERIALIZED(&pipewire_checker_);
+  RTC_CHECK_RUNS_SERIALIZED(&capture_checker_);
 
   while (pw_buffer* buffer = pw_stream_dequeue_buffer(stream_)) {
     struct spa_meta_header* h;
diff --git a/modules/video_capture/linux/video_capture_pipewire.h b/modules/video_capture/linux/video_capture_pipewire.h
index 5d6794ed65..eeb3b9497c 100644
--- a/modules/video_capture/linux/video_capture_pipewire.h
+++ b/modules/video_capture/linux/video_capture_pipewire.h
@@ -43,18 +43,16 @@ class VideoCaptureModulePipeWire : public VideoCaptureImpl {
   void OnFormatChanged(const struct spa_pod* format);
   void ProcessBuffers();
 
-  rtc::RaceChecker pipewire_checker_;
-
   const rtc::scoped_refptr<PipeWireSession> session_
-      RTC_GUARDED_BY(capture_checker_);
+      RTC_GUARDED_BY(api_checker_);
+  bool initialized_ RTC_GUARDED_BY(api_checker_);
+  bool started_ RTC_GUARDED_BY(api_lock_);
   int node_id_ RTC_GUARDED_BY(capture_checker_);
   VideoCaptureCapability configured_capability_
-      RTC_GUARDED_BY(pipewire_checker_);
-  bool initialized_ RTC_GUARDED_BY(capture_checker_);
-  bool started_ RTC_GUARDED_BY(api_lock_);
+      RTC_GUARDED_BY(capture_checker_);
 
-  struct pw_stream* stream_ RTC_GUARDED_BY(pipewire_checker_) = nullptr;
-  struct spa_hook stream_listener_ RTC_GUARDED_BY(pipewire_checker_);
+  struct pw_stream* stream_ RTC_GUARDED_BY(capture_checker_) = nullptr;
+  struct spa_hook stream_listener_ RTC_GUARDED_BY(capture_checker_);
 };
 }  // namespace videocapturemodule
 }  // namespace webrtc