From a54ea933155986a0af84cbd5426f4beebed778e0 Mon Sep 17 00:00:00 2001
From: Vladimir Vukicevic <vladimir@pobox.com>
Date: Tue, 3 Nov 2015 15:13:09 -0500
Subject: [PATCH] Bug 1221160 - fix AutoTraceLogLock deadlock on Windows;
 r=froydnj From e3a1e57c0c8be8214a12e31c6e4950a676efd9bc Mon Sep 17 00:00:00
 2001

MozReview-Commit-ID: JrPiE7eixpy

--HG--
extra : rebase_source : 7f322a0c95c46c0bd1721f982fab8ab421866d70
extra : source : 883ed100b755b9a528104a62ed631beaff6c8cf2
---
 xpcom/base/nsTraceRefcnt.cpp | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/xpcom/base/nsTraceRefcnt.cpp b/xpcom/base/nsTraceRefcnt.cpp
index caa30e000afb..13ba3f7f7871 100644
--- a/xpcom/base/nsTraceRefcnt.cpp
+++ b/xpcom/base/nsTraceRefcnt.cpp
@@ -61,17 +61,24 @@
 // only held for a very short time, and gets grabbed at a very high frequency
 // (~100000 times per second). On Mac, the overhead of using a regular lock
 // is very high, see bug 1137963.
-static mozilla::Atomic<bool, mozilla::ReleaseAcquire> gTraceLogLocked;
+static mozilla::Atomic<uintptr_t, mozilla::ReleaseAcquire> gTraceLogLocked;
 
 struct MOZ_STACK_CLASS AutoTraceLogLock final
 {
+  bool doRelease;
   AutoTraceLogLock()
+    : doRelease(true)
   {
-    while (!gTraceLogLocked.compareExchange(false, true)) {
-      PR_Sleep(PR_INTERVAL_NO_WAIT); /* yield */
+    uintptr_t currentThread = reinterpret_cast<uintptr_t>(PR_GetCurrentThread());
+    if (gTraceLogLocked == currentThread) {
+      doRelease = false;
+    } else {
+      while (!gTraceLogLocked.compareExchange(0, currentThread)) {
+        PR_Sleep(PR_INTERVAL_NO_WAIT); /* yield */
+      }
     }
   }
-  ~AutoTraceLogLock() { gTraceLogLocked = false; }
+  ~AutoTraceLogLock() { if (doRelease) gTraceLogLocked = 0; }
 };
 
 static PLHashTable* gBloatView;
@@ -1119,14 +1126,14 @@ NS_LogAddRef(void* aPtr, nsrefcnt aRefcnt,
 
     bool loggingThisObject = (!gObjectsToLog || LogThisObj(serialno));
     if (aRefcnt == 1 && gAllocLog && loggingThisType && loggingThisObject) {
-      fprintf(gAllocLog, "\n<%s> %p %" PRIdPTR " Create\n", aClass, aPtr, serialno);
+      fprintf(gAllocLog, "\n<%s> %p %" PRIdPTR " Create [thread %p]\n", aClass, aPtr, serialno, PR_GetCurrentThread());
       nsTraceRefcnt::WalkTheStackCached(gAllocLog);
     }
 
     if (gRefcntsLog && loggingThisType && loggingThisObject) {
       // Can't use MOZ_LOG(), b/c it truncates the line
-      fprintf(gRefcntsLog, "\n<%s> %p %" PRIuPTR " AddRef %" PRIuPTR "\n",
-              aClass, aPtr, serialno, aRefcnt);
+      fprintf(gRefcntsLog, "\n<%s> %p %" PRIuPTR " AddRef %" PRIuPTR " [thread %p]\n",
+              aClass, aPtr, serialno, aRefcnt, PR_GetCurrentThread());
       nsTraceRefcnt::WalkTheStackCached(gRefcntsLog);
       fflush(gRefcntsLog);
     }
@@ -1173,8 +1180,8 @@ NS_LogRelease(void* aPtr, nsrefcnt aRefcnt, const char* aClass)
     if (gRefcntsLog && loggingThisType && loggingThisObject) {
       // Can't use MOZ_LOG(), b/c it truncates the line
       fprintf(gRefcntsLog,
-              "\n<%s> %p %" PRIuPTR " Release %" PRIuPTR "\n",
-              aClass, aPtr, serialno, aRefcnt);
+              "\n<%s> %p %" PRIuPTR " Release %" PRIuPTR " [thread %p]\n",
+              aClass, aPtr, serialno, aRefcnt, PR_GetCurrentThread());
       nsTraceRefcnt::WalkTheStackCached(gRefcntsLog);
       fflush(gRefcntsLog);
     }
@@ -1183,7 +1190,7 @@ NS_LogRelease(void* aPtr, nsrefcnt aRefcnt, const char* aClass)
     // yet we still want to see deletion information:
 
     if (aRefcnt == 0 && gAllocLog && loggingThisType && loggingThisObject) {
-      fprintf(gAllocLog, "\n<%s> %p %" PRIdPTR " Destroy\n", aClass, aPtr, serialno);
+      fprintf(gAllocLog, "\n<%s> %p %" PRIdPTR " Destroy [thread %p]\n", aClass, aPtr, serialno, PR_GetCurrentThread());
       nsTraceRefcnt::WalkTheStackCached(gAllocLog);
     }