usb: fix pending transfers queue pop race condition when stopping stream

src/comms/USB/USBDMAEmulation.cpp

@@ -54,6 +54,8 @@ USBDMAEmulation::~USBDMAEmulation()
 void USBDMAEmulation::AbortAllTransfers()
 {
  std::vector<AsyncXfer*> temp;
+
+ std::unique_lock lck{ queuesMutex };
  temp.reserve(pendingXfers.size());
  while (!pendingXfers.empty())
  {
@@ -68,6 +70,8 @@ void USBDMAEmulation::AbortAllTransfers()
  port->FinishDataXfer(async->xfer);
  transfers.push(async);
  }
+ assert(pendingXfers.empty());
+ assert(transfers.size() == maxAsyncTransfers);
 }
 
 std::vector<IDMA::Buffer> USBDMAEmulation::GetBuffers() const
@@ -107,6 +111,7 @@ OpStatus USBDMAEmulation::EnableContinuous(bool enable, uint32_t maxTransferSize
  if (dir != DataTransferDirection::DeviceToHost)
  return OpStatus::Success;
  // For continuous transferring, preemptively request data to be transferred
+ std::unique_lock lck{ queuesMutex };
  while (!transfers.empty())
  {
  AsyncXfer* async = transfers.front();
@@ -123,6 +128,7 @@ OpStatus USBDMAEmulation::EnableContinuous(bool enable, uint32_t maxTransferSize
 
 void USBDMAEmulation::UpdateProducerStates()
 {
+ std::unique_lock lck{ queuesMutex };
  while (!pendingXfers.empty())
  {
  AsyncXfer* async = pendingXfers.front();
@@ -149,7 +155,7 @@ USBDMAEmulation::State USBDMAEmulation::GetCounters()
 OpStatus USBDMAEmulation::SubmitRequest(uint64_t index, uint32_t bytesCount, DataTransferDirection dir, bool irq)
 {
  int count = 1;
-
+ std::unique_lock lck{ queuesMutex };
  count = std::min(size_t(count), transfers.size());
  if (!transfers.empty() && count > 0)
  {
@@ -169,6 +175,7 @@ OpStatus USBDMAEmulation::SubmitRequest(uint64_t index, uint32_t bytesCount, Dat
 
 OpStatus USBDMAEmulation::Wait()
 {
+ std::unique_lock lck{ queuesMutex };
  if (pendingXfers.empty())
  return OpStatus::Success;
 

src/comms/USB/USBDMAEmulation.h

@@ -5,6 +5,7 @@
 
 #include <cstdint>
 #include <memory>
+#include <mutex>
 #include <vector>
 #include <queue>
 
@@ -48,6 +49,7 @@ class USBDMAEmulation : public IDMA
  std::queue<AsyncXfer*> transfers;
  std::queue<AsyncXfer*> pendingXfers;
  std::vector<Buffer> mappings;
+ std::mutex queuesMutex;
 
  void AbortAllTransfers();
  void UpdateProducerStates();