diff --git a/include/llvm/Support/Watchdog.h b/include/llvm/Support/Watchdog.h
new file mode 100644
index 00000000000..b58496b2fb8
--- /dev/null
+++ b/include/llvm/Support/Watchdog.h
@@ -0,0 +1,38 @@
+//===--- Watchdog.h - Watchdog timer ----------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file declares the llvm::sys::Watchdog class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_WATCHDOG_H
+#define LLVM_SUPPORT_WATCHDOG_H
+
+#include "llvm/Support/Compiler.h"
+
+namespace llvm {
+  namespace sys {
+
+    /// This class provides an abstraction for a timeout around an operation
+    /// that must complete in a given amount of time. Failure to complete before
+    /// the timeout is an unrecoverable situation and no mechanisms to attempt
+    /// to handle it are provided.
+    class Watchdog {
+    public:
+      Watchdog(unsigned int seconds);
+      ~Watchdog();
+    private:
+      // Noncopyable.
+      Watchdog(const Watchdog &other) LLVM_DELETED_FUNCTION;
+      Watchdog &operator=(const Watchdog &other) LLVM_DELETED_FUNCTION;
+    };
+  }
+}
+
+#endif
diff --git a/lib/Support/CMakeLists.txt b/lib/Support/CMakeLists.txt
index 5ba69fc3c8c..a83558fafb7 100644
--- a/lib/Support/CMakeLists.txt
+++ b/lib/Support/CMakeLists.txt
@@ -95,6 +95,7 @@ add_llvm_library(LLVMSupport
   Unix/system_error.inc
   Unix/ThreadLocal.inc
   Unix/TimeValue.inc
+  Unix/Watchdog.inc
   Windows/DynamicLibrary.inc
   Windows/Host.inc
   Windows/Memory.inc
@@ -108,4 +109,5 @@ add_llvm_library(LLVMSupport
   Windows/system_error.inc
   Windows/ThreadLocal.inc
   Windows/TimeValue.inc
+  Windows/Watchdog.inc
   )
diff --git a/lib/Support/PrettyStackTrace.cpp b/lib/Support/PrettyStackTrace.cpp
index 21d56adb5e0..23ee5ab105a 100644
--- a/lib/Support/PrettyStackTrace.cpp
+++ b/lib/Support/PrettyStackTrace.cpp
@@ -17,6 +17,7 @@
 #include "llvm/Config/config.h"     // Get autoconf configuration settings
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/ThreadLocal.h"
+#include "llvm/Support/Watchdog.h"
 #include "llvm/Support/raw_ostream.h"
 
 #ifdef HAVE_CRASHREPORTERCLIENT_H
@@ -37,7 +38,10 @@ static unsigned PrintStack(const PrettyStackTraceEntry *Entry, raw_ostream &OS){
   if (Entry->getNextEntry())
     NextID = PrintStack(Entry->getNextEntry(), OS);
   OS << NextID << ".\t";
-  Entry->print(OS);
+  {
+    sys::Watchdog W(5);
+    Entry->print(OS);
+  }
   
   return NextID+1;
 }
diff --git a/lib/Support/Unix/Watchdog.inc b/lib/Support/Unix/Watchdog.inc
new file mode 100644
index 00000000000..5d89c0e51b1
--- /dev/null
+++ b/lib/Support/Unix/Watchdog.inc
@@ -0,0 +1,32 @@
+//===--- Unix/Watchdog.inc - Unix Watchdog Implementation -------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides the generic Unix implementation of the Watchdog class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
+namespace llvm {
+  namespace sys {
+    Watchdog::Watchdog(unsigned int seconds) {
+#ifdef HAVE_UNISTD_H
+      alarm(seconds);
+#endif
+    }
+
+    Watchdog::~Watchdog() {
+#ifdef HAVE_UNISTD_H
+      alarm(0);
+#endif
+    }
+  }
+}
diff --git a/lib/Support/Watchdog.cpp b/lib/Support/Watchdog.cpp
new file mode 100644
index 00000000000..724aa001f16
--- /dev/null
+++ b/lib/Support/Watchdog.cpp
@@ -0,0 +1,23 @@
+//===---- Watchdog.cpp - Implement Watchdog ---------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements the Watchdog class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Watchdog.h"
+#include "llvm/Config/config.h"
+
+// Include the platform-specific parts of this class.
+#ifdef LLVM_ON_UNIX
+#include "Unix/Watchdog.inc"
+#endif
+#ifdef LLVM_ON_WIN32
+#include "Windows/Watchdog.inc"
+#endif
diff --git a/lib/Support/Windows/Watchdog.inc b/lib/Support/Windows/Watchdog.inc
new file mode 100644
index 00000000000..fab2bdf2a94
--- /dev/null
+++ b/lib/Support/Windows/Watchdog.inc
@@ -0,0 +1,24 @@
+//===--- Windows/Watchdog.inc - Windows Watchdog Implementation -*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides the generic Windows implementation of the Watchdog class.
+//
+//===----------------------------------------------------------------------===//
+
+// TODO: implement.
+// Currently this is only used by PrettyStackTrace which is also unimplemented
+// on Windows. Roughly, a Windows implementation would use CreateWaitableTimer
+// and a second thread to run the TimerAPCProc.
+
+namespace llvm {
+  namespace sys {
+    Watchdog::Watchdog(unsigned int seconds) {}
+    Watchdog::~Watchdog() {}
+  }
+}