revert commit f0e6dc6304; overload detection logic was fine already

btw, here's a test script to monitor the persistent context values:

function cycles(which:long) %{
        THIS->__retvalue = (THIS->which == 0) ? CONTEXT->cycles_base :
                                                CONTEXT->cycles_sum;
%}

probe timer.profile { /* just for */ backtrace() /* load generation */
                      printf("%d %d\n", cycles(0), cycles(1)) }
probe timer.s(1) { exit() }

2 files changed, 11 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 033db1b5..4d8d89ae 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2008-04-26  Frank Ch. Eigler  <fche@elastic.org>
+
+	* tapsets.cxx (common_probe_entryfn_prologue): Undo
+	clear of overload-related context vars; add explanation why.
+
 2008-04-25  Frank Ch. Eigler  <fche@elastic.org>
 
 	* systemtap.spec.in: Simplify configuration defaults.
diff --git a/tapsets.cxx b/tapsets.cxx
index 23e85a0e..c10196e2 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -216,10 +216,16 @@ common_probe_entryfn_prologue (translator_output* o, string statestr,
   o->newline() << "#ifdef STP_TIMING";
   o->newline() << "c->statp = 0;";
   o->newline() << "#endif";
+  // NB: The following would actually be incorrect.
+  // That's because cycles_sum/cycles_base values are supposed to survive
+  // between consecutive probes.  Periodically (STP_OVERLOAD_INTERVAL
+  // cycles), the values will be reset.
+  /*
   o->newline() << "#ifdef STP_OVERLOAD";
   o->newline() << "c->cycles_sum = 0;";
   o->newline() << "c->cycles_base = 0;";
   o->newline() << "#endif";  
+  */
 }