[SYCL] Clear event_impl dependencies with graph cleanup (#4793)

When event_impl's d-tor is called its dependencies are starting to recursive releasing. It leads to stack overflow.
Clearing event_impl dependencies in graph cleanup helps to eliminate this problem.
getWaitList was moved to event_impl class so the work with dependencies could be wrapped to mutex.
Test : intel/llvm-test-suite#574
Signed-off-by: mdimakov <[email protected]>

sycl/source/detail/event_impl.cpp

@@ -210,18 +210,24 @@ void event_impl::wait(
 
 void event_impl::wait_and_throw(
     std::shared_ptr<cl::sycl::detail::event_impl> Self) {
-  Command *Cmd = static_cast<Command *>(Self->getCommand());
-  QueueImplPtr submittedQueue = nullptr;
-  if (Cmd)
-    submittedQueue = Cmd->getSubmittedQueue();
+  Scheduler &Sched = Scheduler::getInstance();
 
+  QueueImplPtr submittedQueue = nullptr;
+  {
+    Scheduler::ReadLockT Lock(Sched.MGraphLock);
+    Command *Cmd = static_cast<Command *>(Self->getCommand());
+    if (Cmd)
+      submittedQueue = Cmd->getSubmittedQueue();
+  }
   wait(Self);
 
-  for (auto &EventImpl :
-       detail::Scheduler::getInstance().getWaitList(std::move(Self))) {
-    Command *Cmd = (Command *)EventImpl->getCommand();
-    if (Cmd)
-      Cmd->getSubmittedQueue()->throw_asynchronous();
+  {
+    Scheduler::ReadLockT Lock(Sched.MGraphLock);
+    for (auto &EventImpl : getWaitList()) {
+      Command *Cmd = (Command *)EventImpl->getCommand();
+      if (Cmd)
+        Cmd->getSubmittedQueue()->throw_asynchronous();
+    }
   }
   if (submittedQueue)
     submittedQueue->throw_asynchronous();
@@ -325,6 +331,25 @@ pi_native_handle event_impl::getNative() const {
   return Handle;
 }
 
+std::vector<EventImplPtr> event_impl::getWaitList() {
+  std::lock_guard<std::mutex> Lock(MMutex);
+
+  std::vector<EventImplPtr> Result;
+  Result.reserve(MPreparedDepsEvents.size() + MPreparedHostDepsEvents.size());
+  Result.insert(Result.end(), MPreparedDepsEvents.begin(),
+                MPreparedDepsEvents.end());
+  Result.insert(Result.end(), MPreparedHostDepsEvents.begin(),
+                MPreparedHostDepsEvents.end());
+
+  return Result;
+}
+
+void event_impl::cleanupDependencyEvents() {
+  std::lock_guard<std::mutex> Lock(MMutex);
+  MPreparedDepsEvents.clear();
+  MPreparedHostDepsEvents.clear();
+}
+
 } // namespace detail
 } // namespace sycl
 } // __SYCL_INLINE_NAMESPACE(cl)

sycl/source/detail/event_impl.hpp

@@ -27,6 +27,8 @@ class context_impl;
 using ContextImplPtr = std::shared_ptr<cl::sycl::detail::context_impl>;
 class queue_impl;
 using QueueImplPtr = std::shared_ptr<cl::sycl::detail::queue_impl>;
+class event_impl;
+using EventImplPtr = std::shared_ptr<cl::sycl::detail::event_impl>;
 
 class event_impl {
 public:
@@ -175,6 +177,14 @@ class event_impl {
     return MPreparedHostDepsEvents;
   }
 
+  /// Returns vector of event_impl that this event_impl depends on.
+  ///
+  /// @return a vector of "immediate" dependencies for this event_impl.
+  std::vector<EventImplPtr> getWaitList();
+
+  /// Cleans dependencies of this event_impl
+  void cleanupDependencyEvents();
+
 private:
   // When instrumentation is enabled emits trace event for event wait begin and
   // returns the telemetry event generated for the wait
@@ -192,15 +202,17 @@ class event_impl {
   void *MCommand = nullptr;
 
   /// Dependency events prepared for waiting by backend.
-  std::vector<std::shared_ptr<event_impl>> MPreparedDepsEvents;
-  std::vector<std::shared_ptr<event_impl>> MPreparedHostDepsEvents;
+  std::vector<EventImplPtr> MPreparedDepsEvents;
+  std::vector<EventImplPtr> MPreparedHostDepsEvents;
 
   enum HostEventState : int { HES_NotComplete = 0, HES_Complete };
 
   // State of host event. Employed only for host events and event with no
   // backend's representation (e.g. alloca). Used values are listed in
   // HostEventState enum.
   std::atomic<int> MState;
+
+  std::mutex MMutex;
 };
 
 } // namespace detail

sycl/source/detail/scheduler/graph_builder.cpp

@@ -129,6 +129,7 @@ static void handleVisitedNodes(std::vector<Command *> &Visited) {
   for (Command *Cmd : Visited) {
     if (Cmd->MMarks.MToBeDeleted) {
       Cmd->getEvent()->setCommand(nullptr);
+      Cmd->getEvent()->cleanupDependencyEvents();
       delete Cmd;
     } else
       Cmd->MMarks.MVisited = false;

sycl/source/detail/scheduler/graph_processor.cpp

@@ -21,19 +21,6 @@ static Command *getCommand(const EventImplPtr &Event) {
   return (Command *)Event->getCommand();
 }
 
-std::vector<EventImplPtr>
-Scheduler::GraphProcessor::getWaitList(EventImplPtr Event) {
-  std::vector<EventImplPtr> Result;
-  const std::vector<EventImplPtr> &PDeps = Event->getPreparedDepsEvents();
-  const std::vector<EventImplPtr> &PHDeps = Event->getPreparedHostDepsEvents();
-
-  Result.reserve(PDeps.size() + PHDeps.size());
-  Result.insert(Result.end(), PDeps.begin(), PDeps.end());
-  Result.insert(Result.end(), PHDeps.begin(), PHDeps.end());
-
-  return Result;
-}
-
 void Scheduler::GraphProcessor::waitForEvent(EventImplPtr Event,
                                              ReadLockT &GraphReadLock,
                                              bool LockTheLock) {

sycl/source/detail/scheduler/scheduler.cpp

@@ -206,11 +206,6 @@ Scheduler &Scheduler::getInstance() {
   return GlobalHandler::instance().getScheduler();
 }
 
-std::vector<EventImplPtr> Scheduler::getWaitList(EventImplPtr Event) {
-  ReadLockT Lock(MGraphLock);
-  return GraphProcessor::getWaitList(std::move(Event));
-}
-
 void Scheduler::waitForEvent(EventImplPtr Event) {
   ReadLockT Lock(MGraphLock);
   // It's fine to leave the lock unlocked upon return from waitForEvent as

sycl/source/detail/scheduler/scheduler.hpp

@@ -427,9 +427,6 @@ class Scheduler {
   /// \return an instance of the scheduler object.
   static Scheduler &getInstance();
 
-  /// \return a vector of "immediate" dependencies for the Event given.
-  std::vector<EventImplPtr> getWaitList(EventImplPtr Event);
-
   /// Allocate buffers in the pool for a provided stream
   ///
   /// \param Impl to the stream object
@@ -721,10 +718,6 @@ class Scheduler {
   /// \ingroup sycl_graph
   class GraphProcessor {
   public:
-    /// \return a list of events that represent immediate dependencies of the
-    /// command associated with Event passed.
-    static std::vector<EventImplPtr> getWaitList(EventImplPtr Event);
-
     /// Waits for the command, associated with Event passed, is completed.
     /// \param GraphReadLock read-lock which is already acquired for reading
     /// \param LockTheLock selects if graph lock should be locked upon return
@@ -763,6 +756,7 @@ class Scheduler {
   friend class Command;
   friend class DispatchHostTask;
   friend class queue_impl;
+  friend class event_impl;
 
   /// Stream buffers structure.
   ///

sycl/source/event.cpp

@@ -55,7 +55,7 @@ void event::wait_and_throw(const std::vector<event> &EventList) {
 std::vector<event> event::get_wait_list() {
   std::vector<event> Result;
 
-  for (auto &EventImpl : detail::Scheduler::getInstance().getWaitList(impl))
+  for (auto &EventImpl : impl->getWaitList())
     Result.push_back(detail::createSyclObjFromImpl<event>(EventImpl));
 
   return Result;