From d71932a6ec3aabd2515e4eb94c0d88dc428a41f2 Mon Sep 17 00:00:00 2001
From: Dan Engelbrecht <dan.engelbrecht@epicgames.com>
Date: Mon, 4 Aug 2025 18:37:52 +0200
Subject: Don't set m_DispatchComplete in ParallelWork until after pending work
 countdown succeeds (#455)

---
 src/zenutil/parallelwork.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'src/zenutil/parallelwork.cpp')

diff --git a/src/zenutil/parallelwork.cpp b/src/zenutil/parallelwork.cpp
index aa806438b..1edca5050 100644
--- a/src/zenutil/parallelwork.cpp
+++ b/src/zenutil/parallelwork.cpp
@@ -33,6 +33,7 @@ ParallelWork::~ParallelWork()
 				"ParallelWork disposed without explicit wait for completion, likely caused by an exception, waiting for dispatched threads "
 				"to complete");
 			m_PendingWork.CountDown();
+			m_DispatchComplete = true;
 		}
 		m_PendingWork.Wait();
 		ptrdiff_t RemainingWork = m_PendingWork.Remaining();
@@ -82,10 +83,9 @@ void
 ParallelWork::Wait(int32_t UpdateIntervalMS, UpdateCallback&& UpdateCallback)
 {
 	ZEN_ASSERT(!m_DispatchComplete);
-	m_DispatchComplete = true;
-
 	ZEN_ASSERT(m_PendingWork.Remaining() > 0);
 	m_PendingWork.CountDown();
+	m_DispatchComplete = true;
 
 	while (!m_PendingWork.Wait(UpdateIntervalMS))
 	{
@@ -99,10 +99,10 @@ void
 ParallelWork::Wait()
 {
 	ZEN_ASSERT(!m_DispatchComplete);
-	m_DispatchComplete = true;
-
 	ZEN_ASSERT(m_PendingWork.Remaining() > 0);
 	m_PendingWork.CountDown();
+	m_DispatchComplete = true;
+
 	m_PendingWork.Wait();
 
 	RethrowErrors();
-- 
cgit v1.2.3


From 3a2d008eb35ff3635c7336ac684873c0e315e5c2 Mon Sep 17 00:00:00 2001
From: Dan Engelbrecht <dan.engelbrecht@epicgames.com>
Date: Wed, 6 Aug 2025 10:52:24 +0200
Subject: more details in parallel work when wait fails/destructor has
 inconsistent state (#457)

---
 src/zenutil/parallelwork.cpp | 42 ++++++++++++++++++++++++++++++------------
 1 file changed, 30 insertions(+), 12 deletions(-)

(limited to 'src/zenutil/parallelwork.cpp')

diff --git a/src/zenutil/parallelwork.cpp b/src/zenutil/parallelwork.cpp
index 1edca5050..a571d1d11 100644
--- a/src/zenutil/parallelwork.cpp
+++ b/src/zenutil/parallelwork.cpp
@@ -35,17 +35,19 @@ ParallelWork::~ParallelWork()
 			m_PendingWork.CountDown();
 			m_DispatchComplete = true;
 		}
-		m_PendingWork.Wait();
-		ptrdiff_t RemainingWork = m_PendingWork.Remaining();
+		const bool		WaitSucceeded = m_PendingWork.Wait();
+		const ptrdiff_t RemainingWork = m_PendingWork.Remaining();
+		if (!WaitSucceeded)
+		{
+			ZEN_ERROR("ParallelWork::~ParallelWork(): waiting for latch failed, pending work count at {}", RemainingWork);
+		}
 		if (RemainingWork != 0)
 		{
 			void*			 Frames[8];
 			uint32_t		 FrameCount = GetCallstack(2, 8, Frames);
 			CallstackFrames* Callstack	= CreateCallstack(FrameCount, Frames);
-			ZEN_ERROR("ParallelWork destructor waited for outstanding work but pending work count is {} instead of 0\n{}",
-					  RemainingWork,
-					  CallstackToString(Callstack, "  "));
-			FreeCallstack(Callstack);
+			auto			 _			= MakeGuard([Callstack]() { FreeCallstack(Callstack); });
+			ZEN_WARN("ParallelWork::~ParallelWork(): waited for outstanding work but pending work count is {} instead of 0", RemainingWork);
 
 			uint32_t WaitedMs = 0;
 			while (m_PendingWork.Remaining() > 0 && WaitedMs < 2000)
@@ -53,20 +55,27 @@ ParallelWork::~ParallelWork()
 				Sleep(50);
 				WaitedMs += 50;
 			}
-			RemainingWork = m_PendingWork.Remaining();
-			if (RemainingWork != 0)
+			ptrdiff_t RemainingWorkAfterSafetyWait = m_PendingWork.Remaining();
+			if (RemainingWorkAfterSafetyWait != 0)
 			{
-				ZEN_WARN("ParallelWork destructor safety wait failed, pending work count at {}", RemainingWork)
+				ZEN_ERROR("ParallelWork::~ParallelWork(): safety wait for {} tasks failed, pending work count at {} after {}\n{}",
+						  RemainingWork,
+						  RemainingWorkAfterSafetyWait,
+						  NiceLatencyNs(WaitedMs * 1000000u),
+						  CallstackToString(Callstack, "  "))
 			}
 			else
 			{
-				ZEN_INFO("ParallelWork destructor safety wait succeeded");
+				ZEN_ERROR("ParallelWork::~ParallelWork(): safety wait for {} tasks completed after {}\n{}",
+						  RemainingWork,
+						  NiceLatencyNs(WaitedMs * 1000000u),
+						  CallstackToString(Callstack, "  "));
 			}
 		}
 	}
 	catch (const std::exception& Ex)
 	{
-		ZEN_ERROR("Exception in ~ParallelWork: {}", Ex.what());
+		ZEN_ERROR("Exception in ParallelWork::~ParallelWork(): {}", Ex.what());
 	}
 }
 
@@ -103,7 +112,16 @@ ParallelWork::Wait()
 	m_PendingWork.CountDown();
 	m_DispatchComplete = true;
 
-	m_PendingWork.Wait();
+	const bool		WaitSucceeded = m_PendingWork.Wait();
+	const ptrdiff_t RemainingWork = m_PendingWork.Remaining();
+	if (!WaitSucceeded)
+	{
+		ZEN_ERROR("ParallelWork::Wait(): waiting for latch failed, pending work count at {}", RemainingWork);
+	}
+	else if (RemainingWork != 0)
+	{
+		ZEN_ERROR("ParallelWork::Wait(): pending work count at {} after successful wait for latch", RemainingWork);
+	}
 
 	RethrowErrors();
 }
-- 
cgit v1.2.3