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, 2 insertions, 15 deletions

diff --git a/tapset/timestamp_gtod.stp b/tapset/timestamp_gtod.stp
index 43b127dc..b916a3b1 100644
--- a/tapset/timestamp_gtod.stp
+++ b/tapset/timestamp_gtod.stp
@@ -7,23 +7,10 @@
 // Public License (GPL); either version 2, or (at your option) any
 // later version.
 
-function _gettimeofday_init:long() %{
-  THIS->__retvalue = _stp_init_time(); /* Kick off the Big Bang.  */
+%{
+#define STAP_NEED_GETTIMEOFDAY 1
 %}
 
-probe begin(-0x8000000000000000) {
-  if (_gettimeofday_init() != 0)
-    error("couldn't initialize gettimeofday")
-}
-
-function _gettimeofday_kill() %{
-  _stp_kill_time();  /* Go to a beach.  Drink a beer.  */
-%}
-
-probe end(0x7FFFFFFFFFFFFFFF), error(0x7FFFFFFFFFFFFFFF) {
-  _gettimeofday_kill()
-}
-
 
 /**
  * sfunction gettimeofday_ns - Number of nanoseconds since UNIX epoch.