diff -up mozilla-beta/xpcom/threads/ThreadStackHelper.cpp.rt-tgsigqueueinfo mozilla-beta/xpcom/threads/ThreadStackHelper.cpp
--- mozilla-beta/xpcom/threads/ThreadStackHelper.cpp.rt-tgsigqueueinfo	2015-04-16 23:45:29.000000000 +0200
+++ mozilla-beta/xpcom/threads/ThreadStackHelper.cpp	2015-04-22 09:10:25.291166226 +0200
@@ -240,10 +240,13 @@ ThreadStackHelper::GetStack(Stack& aStac
   uinfo.si_pid = getpid();
   uinfo.si_uid = getuid();
   uinfo.si_value.sival_ptr = this;
+#ifdef SYS_rt_tgsigqueueinfo
   if (::syscall(SYS_rt_tgsigqueueinfo, uinfo.si_pid,
-                mThreadID, sFillStackSignum, &uinfo)) {
+                mThreadID, sFillStackSignum, &uinfo))
     // rt_tgsigqueueinfo was added in Linux 2.6.31.
     // Could have failed because the syscall did not exist.
+#endif
+  {
     return;
   }
   MOZ_ALWAYS_TRUE(!::sem_wait(&mSem));