From 556c152c54e20ae1173e565720341f6fe3f8590e Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <nnethercote@mozilla.com>
Date: Thu, 13 Dec 2012 19:42:47 -0800
Subject: [PATCH] Bug 821577 - DMD: Fix hang at start-up on Mac.  r=jlebar.

--HG--
extra : rebase_source : 39b46f3a7b8aead6e971f55cb0821f443b7368dc
---
 memory/replace/dmd/DMD.cpp | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/memory/replace/dmd/DMD.cpp b/memory/replace/dmd/DMD.cpp
index f78424ac4c10..8e62ec6fd34a 100644
--- a/memory/replace/dmd/DMD.cpp
+++ b/memory/replace/dmd/DMD.cpp
@@ -1637,6 +1637,13 @@ BadArg(const char* aArg)
   exit(1);
 }
 
+#ifdef XP_MACOSX
+static void
+NopStackWalkCallback(void* aPc, void* aSp, void* aClosure)
+{
+}
+#endif
+
 // Note that fopen() can allocate.
 static FILE*
 OpenTestOrStressFile(const char* aFilename)
@@ -1729,6 +1736,16 @@ Init(const malloc_table_t* aMallocTable)
 
   StatusMsg("DMD is enabled\n");
 
+#ifdef XP_MACOSX
+  // On Mac OS X we need to call StackWalkInitCriticalAddress() very early
+  // (prior to the creation of any mutexes, apparently) otherwise we can get
+  // hangs when getting stack traces (bug 821577).  But
+  // StackWalkInitCriticalAddress() isn't exported from xpcom/, so instead we
+  // just call NS_StackWalk, because that calls StackWalkInitCriticalAddress().
+  // See the comment above StackWalkInitCriticalAddress() for more details.
+  (void)NS_StackWalk(NopStackWalkCallback, 0, nullptr, 0, nullptr);
+#endif
+
   gStateLock = InfallibleAllocPolicy::new_<Mutex>();
 
   gSmallBlockActualSizeCounter = 0;