timeval: Fix occasional backtrace() related deadlock.

Occasionally, backtrace() will deadlock in the signal handler
because it does some non signal safe initialization.  Specifically,
it opens a shared object.  As a work around, this patch forces
backtrace() to run outside of a signal handler, so that future
calls will perform as expected.

Signed-off-by: Ethan Jackson <ethan@nicira.com>

lib/timeval.c

@@ -121,6 +121,16 @@ time_init(void)
     }
     inited = true;
 
+    /* The implementation of backtrace() in glibc does some one time
+     * initialization which is not signal safe.  This can cause deadlocks if
+     * run from the signal handler.  As a workaround, force the initialization
+     * to happen here. */
+    if (HAVE_EXECINFO_H) {
+        void *bt[1];
+
+        backtrace(bt, ARRAY_SIZE(bt));
+    }
+
     memset(traces, 0, sizeof traces);
 
     if (HAVE_EXECINFO_H && CACHE_TIME) {