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, 13 insertions, 0 deletions

diff --git a/testsuite/buildok/gtod_noinit.stp b/testsuite/buildok/gtod_noinit.stp
new file mode 100755
index 00000000..94a9dfdc
--- /dev/null
+++ b/testsuite/buildok/gtod_noinit.stp
@@ -0,0 +1,13 @@
+#! stap -gp4
+
+# check that STAP_NEED_GETTIMEOFDAY is NOT defined without a gettimeofday
+function check() %{
+#ifdef STAP_NEED_GETTIMEOFDAY
+#error "STAP_NEED_GETTIMEOFDAY should not be defined!"
+#endif
+%}
+
+probe begin {
+    check()
+    println(get_cycles())
+}