Patch-Source: https://gist.github.com/classilla/1202f8d467749c029325278a87a068c8
--
--- a/toolkit/components/terminator/nsTerminator.cpp
+++ b/toolkit/components/terminator/nsTerminator.cpp
@@ -455,16 +455,21 @@
       // Defend against overflow
       crashAfterMS = INT32_MAX;
     } else {
       crashAfterMS *= scaleUp;
     }
   }
 #endif
 
+  // Disable watchdog for PGO train builds - writting profile information at
+  // exit may take time and it is better to make build hang rather than
+  // silently produce poorly performing binary.
+  crashAfterMS = INT32_MAX;
+
   UniquePtr<Options> options(new Options());
   // crashAfterTicks is guaranteed to be > 0 as
   // crashAfterMS >= ADDITIONAL_WAIT_BEFORE_CRASH_MS >> HEARTBEAT_INTERVAL_MS
   options->crashAfterTicks = crashAfterMS / HEARTBEAT_INTERVAL_MS;
 
   DebugOnly<PRThread*> watchdogThread =
       CreateSystemThread(RunWatchdog, options.release());
   MOZ_ASSERT(watchdogThread);