PR10177: init/kill time in sleepy context only

Previously, _stp_init_time and _stp_kill_time were being called from
begin/end/error probes, which will run with preemption disabled.  The
BUG reported on RT kernels showed that cpufreq_unregister_notifier can
end up sleeping, which violates our preemption block.

This patch moves the init/kill into systemtap_module_init/exit, where it
is safe to sleep.  The code maintains a new predicate with the define
STAP_NEED_GETTIMEOFDAY, so we don't still incur any timer overhead if
it's not used.

1 files changed, 14 insertions, 0 deletions

diff --git a/translate.cxx b/translate.cxx
index 62c71aeb..9f45f5d1 100644
--- a/translate.cxx
+++ b/translate.cxx
@@ -1133,6 +1133,15 @@ c_unparser::emit_module_init ()
   o->newline(-1) << "}";
   o->newline() << "if (rc) goto out;";
 
+  // initialize gettimeofday (if needed)
+  o->newline() << "#ifdef STAP_NEED_GETTIMEOFDAY";
+  o->newline() << "rc = _stp_init_time();";  // Kick off the Big Bang.
+  o->newline() << "if (rc) {";
+  o->newline(1) << "_stp_error (\"couldn't initialize gettimeofday\");";
+  o->newline() << "goto out;";
+  o->newline(-1) << "}";
+  o->newline() << "#endif";
+
   o->newline() << "(void) probe_point;";
   o->newline() << "(void) i;";
   o->newline() << "(void) j;";
@@ -1359,6 +1368,11 @@ c_unparser::emit_module_exit ()
     o->newline() << "#endif";
   }
 
+  // teardown gettimeofday (if needed)
+  o->newline() << "#ifdef STAP_NEED_GETTIMEOFDAY";
+  o->newline() << " _stp_kill_time();";  // Go to a beach.  Drink a beer.
+  o->newline() << "#endif";
+
   // print final error/skipped counts if non-zero
   o->newline() << "if (atomic_read (& skipped_count) || "
                << "atomic_read (& error_count) || "