8240295: hs_err elapsed time in seconds is not accurate enough

Backport-of: a11912c

Author: Larry-N

src/hotspot/share/runtime/os.cpp

@@ -999,10 +999,9 @@ void os::print_date_and_time(outputStream *st, char* buf, size_t buflen) {
   }
 
   double t = os::elapsedTime();
-  // NOTE: It tends to crash after a SEGV if we want to printf("%f",...) in
-  //       Linux. Must be a bug in glibc ? Workaround is to round "t" to int
-  //       before printf. We lost some precision, but who cares?
+  // NOTE: a crash using printf("%f",...) on Linux was historically noted here.
   int eltime = (int)t;  // elapsed time in seconds
+  int eltimeFraction = (int) ((t - eltime) * 1000000);
 
   // print elapsed time in a human-readable format:
   int eldays = eltime / secs_per_day;
@@ -1012,7 +1011,7 @@ void os::print_date_and_time(outputStream *st, char* buf, size_t buflen) {
   int elmins = (eltime - day_secs - hour_secs) / secs_per_min;
   int minute_secs = elmins * secs_per_min;
   int elsecs = (eltime - day_secs - hour_secs - minute_secs);
-  st->print_cr(" elapsed time: %d seconds (%dd %dh %dm %ds)", eltime, eldays, elhours, elmins, elsecs);
+  st->print_cr(" elapsed time: %d.%06d seconds (%dd %dh %dm %ds)", eltime, eltimeFraction, eldays, elhours, elmins, elsecs);
 }