From 32de9efebce4afadb599a2a24d85d65468a4ad5a Mon Sep 17 00:00:00 2001
From: Jamie Madill <jmadill@chromium.org>
Date: Thu, 17 Sep 2020 12:03:12 -0400
Subject: [PATCH] Guard against race in perf warnings.

Expose the "debug" mutex so insertPerfWarning can use it.

This was detected using TSAN and MultithreadingTest.

Bug: b/168744561
Change-Id: Idde95a7b217f21f007893192a4a1f0a69b4ed3a9
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2415184
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
---
 src/common/debug.cpp   |  7 ++++++-
 src/common/debug.h     |  3 +++
 src/libANGLE/Debug.cpp | 20 +++++++++++++++-----
 3 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/src/common/debug.cpp b/src/common/debug.cpp
index a2f8bba29..e14a9e39f 100644
--- a/src/common/debug.cpp
+++ b/src/common/debug.cpp
@@ -14,7 +14,6 @@
 #include <cstdio>
 #include <cstring>
 #include <fstream>
-#include <mutex>
 #include <ostream>
 #include <vector>
 
@@ -114,6 +113,12 @@ void InitializeDebugMutexIfNeeded()
     }
 }
 
+std::mutex &GetDebugMutex()
+{
+    ASSERT(g_debugMutex);
+    return *g_debugMutex;
+}
+
 ScopedPerfEventHelper::ScopedPerfEventHelper(const char *format, ...) : mFunctionName(nullptr)
 {
     bool dbgTrace = DebugAnnotationsActive();
diff --git a/src/common/debug.h b/src/common/debug.h
index 3e7e18b31..59a5000a0 100644
--- a/src/common/debug.h
+++ b/src/common/debug.h
@@ -15,6 +15,7 @@
 
 #include <iomanip>
 #include <ios>
+#include <mutex>
 #include <sstream>
 #include <string>
 
@@ -103,6 +104,8 @@ bool DebugAnnotationsInitialized();
 
 void InitializeDebugMutexIfNeeded();
 
+std::mutex &GetDebugMutex();
+
 namespace priv
 {
 // This class is used to explicitly ignore values in the conditional logging macros. This avoids
diff --git a/src/libANGLE/Debug.cpp b/src/libANGLE/Debug.cpp
index 1443bb387..5125b2164 100644
--- a/src/libANGLE/Debug.cpp
+++ b/src/libANGLE/Debug.cpp
@@ -340,18 +340,28 @@ size_t Debug::getGroupStackDepth() const
 
 void Debug::insertPerfWarning(GLenum severity, const char *message, uint32_t *repeatCount) const
 {
-    constexpr uint32_t kMaxRepeat = 4;
-    if (*repeatCount >= kMaxRepeat)
+    bool repeatLast;
+
     {
-        return;
+        constexpr uint32_t kMaxRepeat = 4;
+        std::lock_guard<std::mutex> lock(GetDebugMutex());
+
+        if (*repeatCount >= kMaxRepeat)
+        {
+            return;
+        }
+
+        ++*repeatCount;
+        repeatLast = (*repeatCount == kMaxRepeat);
     }
 
-    ++*repeatCount;
     std::string msg = message;
-    if (*repeatCount == kMaxRepeat)
+    if (repeatLast)
     {
         msg += " (this message will no longer repeat)";
     }
+
+    // Release the lock before we call insertMessage. It will re-acquire the lock.
     insertMessage(GL_DEBUG_SOURCE_API, GL_DEBUG_TYPE_PERFORMANCE, 0, severity, std::move(msg),
                   gl::LOG_INFO);
 }