Add thread checks to FifoBuffer (test-only class)

These checks replace the need for a mutex as the usage of the
StreamInterface methods is consistently on the same thread as
the callbacks.

Bug: none
Change-Id: I0c5aaddcbdaa4a6a84c3bc73306563a9f8a8821d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/347902
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#42148}

rtc_base/memory/BUILD.gn

@@ -36,7 +36,6 @@ rtc_library("fifo_buffer") {
     "..:stream",
     "..:threading",
     "../../api/task_queue:pending_task_safety_flag",
-    "../synchronization:mutex",
   ]
 }
 

rtc_base/memory/fifo_buffer.cc

@@ -39,20 +39,20 @@ FifoBuffer::FifoBuffer(size_t size, Thread* owner)
 FifoBuffer::~FifoBuffer() {}
 
 bool FifoBuffer::GetBuffered(size_t* size) const {
-  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK_RUN_ON(&callback_sequence_);
   *size = data_length_;
   return true;
 }
 
 StreamState FifoBuffer::GetState() const {
-  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK_RUN_ON(&callback_sequence_);
   return state_;
 }
 
 StreamResult FifoBuffer::Read(rtc::ArrayView<uint8_t> buffer,
                               size_t& bytes_read,
                               int& error) {
-  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK_RUN_ON(&callback_sequence_);
   const bool was_writable = data_length_ < buffer_length_;
   size_t copy = 0;
   StreamResult result = ReadLocked(buffer.data(), buffer.size(), &copy);
@@ -75,7 +75,7 @@ StreamResult FifoBuffer::Read(rtc::ArrayView<uint8_t> buffer,
 StreamResult FifoBuffer::Write(rtc::ArrayView<const uint8_t> buffer,
                                size_t& bytes_written,
                                int& error) {
-  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK_RUN_ON(&callback_sequence_);
 
   const bool was_readable = (data_length_ > 0);
   size_t copy = 0;
@@ -94,12 +94,12 @@ StreamResult FifoBuffer::Write(rtc::ArrayView<const uint8_t> buffer,
 }
 
 void FifoBuffer::Close() {
-  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK_RUN_ON(&callback_sequence_);
   state_ = SS_CLOSED;
 }
 
 const void* FifoBuffer::GetReadData(size_t* size) {
-  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK_RUN_ON(&callback_sequence_);
   *size = (read_position_ + data_length_ <= buffer_length_)
               ? data_length_
               : buffer_length_ - read_position_;
@@ -107,8 +107,8 @@ const void* FifoBuffer::GetReadData(size_t* size) {
 }
 
 void FifoBuffer::ConsumeReadData(size_t size) {
-  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK_RUN_ON(&callback_sequence_);
-  RTC_DCHECK(size <= data_length_);
+  RTC_DCHECK_LE(size, data_length_);
   const bool was_writable = data_length_ < buffer_length_;
   read_position_ = (read_position_ + size) % buffer_length_;
   data_length_ -= size;
@@ -118,7 +118,8 @@ void FifoBuffer::ConsumeReadData(size_t size) {
 }
 
 void* FifoBuffer::GetWriteBuffer(size_t* size) {
-  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK_RUN_ON(&callback_sequence_);
+
   if (state_ == SS_CLOSED) {
     return nullptr;
   }
@@ -138,8 +139,8 @@ void* FifoBuffer::GetWriteBuffer(size_t* size) {
 }
 
 void FifoBuffer::ConsumeWriteBuffer(size_t size) {
-  webrtc::MutexLock lock(&mutex_);
+  RTC_DCHECK_RUN_ON(&callback_sequence_);
-  RTC_DCHECK(size <= buffer_length_ - data_length_);
+  RTC_DCHECK_LE(size, buffer_length_ - data_length_);
   const bool was_readable = (data_length_ > 0);
   data_length_ += size;
   if (!was_readable && size > 0) {

rtc_base/memory/fifo_buffer.h

@@ -15,7 +15,6 @@
 
 #include "api/task_queue/pending_task_safety_flag.h"
 #include "rtc_base/stream.h"
-#include "rtc_base/synchronization/mutex.h"
 
 namespace rtc {
 
@@ -78,6 +77,7 @@ class FifoBuffer final : public StreamInterface {
 
  private:
   void PostEvent(int events, int err) {
+    RTC_DCHECK_RUN_ON(owner_);
     owner_->PostTask(
         webrtc::SafeTask(task_safety_.flag(), [this, events, err]() {
           RTC_DCHECK_RUN_ON(&callback_sequence_);
@@ -88,31 +88,29 @@ class FifoBuffer final : public StreamInterface {
   // Helper method that implements Read. Caller must acquire a lock
   // when calling this method.
   StreamResult ReadLocked(void* buffer, size_t bytes, size_t* bytes_read)
-      RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(callback_sequence_);
 
   // Helper method that implements Write. Caller must acquire a lock
   // when calling this method.
   StreamResult WriteLocked(const void* buffer,
                            size_t bytes,
                            size_t* bytes_written)
-      RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+      RTC_EXCLUSIVE_LOCKS_REQUIRED(callback_sequence_);
 
   webrtc::ScopedTaskSafety task_safety_;
 
   // keeps the opened/closed state of the stream
-  StreamState state_ RTC_GUARDED_BY(mutex_);
+  StreamState state_ RTC_GUARDED_BY(callback_sequence_);
   // the allocated buffer
-  std::unique_ptr<char[]> buffer_ RTC_GUARDED_BY(mutex_);
+  std::unique_ptr<char[]> buffer_ RTC_GUARDED_BY(callback_sequence_);
   // size of the allocated buffer
   const size_t buffer_length_;
   // amount of readable data in the buffer
-  size_t data_length_ RTC_GUARDED_BY(mutex_);
+  size_t data_length_ RTC_GUARDED_BY(callback_sequence_);
   // offset to the readable data
-  size_t read_position_ RTC_GUARDED_BY(mutex_);
+  size_t read_position_ RTC_GUARDED_BY(callback_sequence_);
   // stream callbacks are dispatched on this thread
   Thread* const owner_;
-  // object lock
-  mutable webrtc::Mutex mutex_;
 };
 
 }  // namespace rtc