2006-01-03 Frank Ch. Eigler <fche@redhat.com>

	PR 1144, 1379
	* tapsets.cxx (emit_probe_prologue, _epilogue): New routines.
	Call from existing derived_probe spots.  Implement soft errors in
	epilogue code.  Implement reentrancy detection in prologue code.
	(dwarf_derived_probe::emit_deregistration): Add kprobes layer
	"nmissed" to skipped_count.
	* translate.cxx (varlock): Use nsleep(TRYLOCKDELAY) in lock
	contention loop.
	(emit_module_exit): Report number of soft errors and skipped probes.
	(emit_function, _probe): Add __restrict__ marker to context pointer.
	(translate_pass): Define new MAXTRYLOCK, TRYLOCKDELAY, MAXERRORS,
	MAXSKIPPED parameters.
	* tapset/logging.stp (error): Don't stp_error, just set context state.
	* stap.1.in, stapfuncs.5.in: Document soft errors.
	* elaborate.h: Corresponding changes.

2006-01-03  Frank Ch. Eigler  <fche@redhat.com>

	* io.c (_stp_softerror): New function.

2006-01-03  Frank Ch. Eigler  <fche@redhat.com>

	* systemtap.base/timers.exp: Extend the test run duration.
	Accept skipped probe warnings at shutdown.

9 files changed, 193 insertions, 139 deletions

diff --git a/ChangeLog b/ChangeLog
index 9489c0d8..e1f6ed91 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,21 @@
+2006-01-03  Frank Ch. Eigler  <fche@redhat.com>
+
+	PR 1144, 1379
+	* tapsets.cxx (emit_probe_prologue, _epilogue): New routines.
+	Call from existing derived_probe spots.  Implement soft errors in
+	epilogue code.  Implement reentrancy detection in prologue code.
+	(dwarf_derived_probe::emit_deregistration): Add kprobes layer
+	"nmissed" to skipped_count.
+	* translate.cxx (varlock): Use nsleep(TRYLOCKDELAY) in lock
+	contention loop.
+	(emit_module_exit): Report number of soft errors and skipped probes.
+	(emit_function, _probe): Add __restrict__ marker to context pointer.
+	(translate_pass): Define new MAXTRYLOCK, TRYLOCKDELAY, MAXERRORS,
+	MAXSKIPPED parameters.
+	* tapset/logging.stp (error): Don't stp_error, just set context state.
+	* stap.1.in, stapfuncs.5.in: Document soft errors.
+	* elaborate.h: Corresponding changes.
+
 2005-12-23  Kevin Stafford  <krstaffo@us.ibm.com>
 
 	* tapset/2.6.9-20.ELsmp/syscalls.stp: added kernel
diff --git a/elaborate.h b/elaborate.h
index f2a4bd56..afaf8b18 100644
--- a/elaborate.h
+++ b/elaborate.h
@@ -1,5 +1,5 @@
 // -*- C++ -*-
-// Copyright (C) 2005 Red Hat Inc.
+// Copyright (C) 2005, 2006 Red Hat Inc.
 //
 // This file is part of systemtap, and is free software.  You can
 // redistribute it and/or modify it under the terms of the GNU General
@@ -128,11 +128,14 @@ struct derived_probe: public probe
                                    unsigned probeidx) = 0;
   // ... for all probe-points:
   // ELABORATE_SPECIFIC_SIGNATURE ENTRYFN {
-  //   /* allocate context */
+  //   /* allocate context - probe_prologue */
   //   /* copy parameters, initial state into context */
   //   probe_NUMBER (context);
-  //   /* deallocate context */
+  //   /* deallocate context - probe_epilogue */
   // }
+
+  void emit_probe_prologue (translator_output* o, const std::string&);
+  void emit_probe_epilogue (translator_output* o);
 };
 
 // ------------------------------------------------------------------------
diff --git a/runtime/ChangeLog b/runtime/ChangeLog
index 7155d74c..07973c93 100644
--- a/runtime/ChangeLog
+++ b/runtime/ChangeLog
@@ -1,3 +1,7 @@
+2006-01-03  Frank Ch. Eigler  <fche@redhat.com>
+
+	* io.c (_stp_softerror): New function.
+
 2005-12-14  Martin Hunt  <hunt@redhat.com>
 
 	* pmap-gen.c (_stp_pmap_new_*): Initialize lock.
diff --git a/runtime/io.c b/runtime/io.c
index cf178951..b72590f3 100644
--- a/runtime/io.c
+++ b/runtime/io.c
@@ -1,6 +1,6 @@
 /* -*- linux-c -*- 
  * I/O for printing warnings, errors and debug messages
- * Copyright (C) 2005 Red Hat Inc.
+ * Copyright (C) 2005, 2006 Red Hat Inc.
  *
  * This file is part of systemtap, and is free software.  You can
  * redistribute it and/or modify it under the terms of the GNU General
@@ -138,6 +138,25 @@ void _stp_error (const char *fmt, ...)
 	_stp_exit();
 }
 
+
+/** Prints error message.
+ * This function sends an error message immediately to stpd. It
+ * will also be sent over the bulk transport (relayfs) if it is
+ * being used. If the last character is not a newline, then one 
+ * is added. 
+ *
+ * @param fmt A variable number of args.
+ * @sa _stp_error
+ */
+void _stp_softerror (const char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	_stp_vlog (ERROR, NULL, 0, fmt, args);
+	va_end(args);
+}
+
+
 static void _stp_dbug (char *func, int line, const char *fmt, ...)
 {
 	va_list args;
diff --git a/stap.1.in b/stap.1.in
index e90bb09e..69c1e6d2 100644
--- a/stap.1.in
+++ b/stap.1.in
@@ -50,7 +50,7 @@ a named file, from standard input, or from the command line.  The
 program runs until it is interrupted by the user, or if the script
 voluntarily invokes the
 .I exit()
-function, or by any fatal error.
+function, or by sufficient number of soft errors.
 .PP
 The language, which is described in a later section, is strictly typed,
 declaration free, procedural, and inspired by
@@ -639,8 +639,9 @@ the module then communicates with it, copying trace data from the
 kernel into temporary files, until the user sends an interrupt signal.
 Any run-time error encountered by the probe handlers, such as running
 out of memory, division by zero, exceeding nesting or runtime limits,
-results in an error condition that prevents further probes from
-running.  Finally, stpd unloads the module, and cleans up.
+results in a soft error indication.  Soft errors in excess of
+MAXERRORS block of all subsequent probes, and terminate the session.
+Finally, stpd unloads the module, and cleans up.
 
 .SH EXAMPLES
 See the 
@@ -692,6 +693,12 @@ Maximum number of statements to execute during any single probe hit.
 .TP
 MAXMAPENTRIES
 Maximum number of rows in any single global array.
+.TP
+MAXERRORS
+Maximum number of soft errors before an exit is triggered.
+.TP
+MAXSKIPPED
+Maximum number of skipped reentrant probes before an exit is triggered.
 
 .PP
 In case something goes wrong with 
diff --git a/stapfuncs.5.in b/stapfuncs.5.in
index 806a0906..56d6aed5 100644
--- a/stapfuncs.5.in
+++ b/stapfuncs.5.in
@@ -48,13 +48,13 @@ prepends the string "WARNING:".
 
 .TP
 error:unknown (msg:string)
-A fatal error has occurred.  Log the given string to the error stream.
+An error has occurred.  Log the given string to the error stream.
 Append an implicit end-of-line.
 .I stpd
 prepends the string "ERROR:".
-Block any further execution of statements in this probe, block
-any new probe handlers, and end the systemtap session as soon
-as possible.
+Block any further execution of statements in this probe.  If the number
+of errors so far exceeds the MAXERRORS parameter, also trigger an 
+.IR exit() .
 
 .TP
 exit:unknown ()
diff --git a/tapset/logging.stp b/tapset/logging.stp
index 54f4c272..c9c60c8d 100644
--- a/tapset/logging.stp
+++ b/tapset/logging.stp
@@ -1,5 +1,5 @@
 // logging tapset
-// Copyright (C) 2005 Red Hat Inc.
+// Copyright (C) 2005, 2006 Red Hat Inc.
 //
 // This file is part of systemtap, and is free software.  You can
 // redistribute it and/or modify it under the terms of the GNU General
@@ -26,6 +26,12 @@ function exit () %{
 %}
 
 function error (msg:string) %{
-    CONTEXT->last_error = "called error()"; /* kill current probe */
-    _stp_error ("%s", THIS->msg); /* implies _stp_exit */
+    /* This is an assignment of a local char[] to a global char*.
+       It would normally be just as unsafe as returning a pointer to
+       a local variable from a function.  However, the translated
+       code ensures that upon an error (last_error != NULL), the
+       context stack is only ever unwound, and not reused, before
+       the probe-level stp-error call.  */
+    CONTEXT->last_error = THIS->msg;
+    CONTEXT->last_stmt = NULL;
 %}
diff --git a/tapsets.cxx b/tapsets.cxx
index fcf84820..a6c57b80 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -1,5 +1,5 @@
 // tapset resolution
-// Copyright (C) 2005 Red Hat Inc.
+// Copyright (C) 2005, 2006 Red Hat Inc.
 // Copyright (C) 2005 Intel Corporation.
 //
 // This file is part of systemtap, and is free software.  You can
@@ -86,6 +86,63 @@ lex_cast_qstring(IN const & in)
 
 
 // ------------------------------------------------------------------------
+
+void
+derived_probe::emit_probe_prologue (translator_output* o,
+                                    const std::string& statereq)
+{
+  o->newline() << "struct context* c = per_cpu_ptr "
+               << "(contexts, smp_processor_id());";
+  o->newline() << "if (atomic_read (&session_state) != " << statereq << ")";
+  o->newline(1) << "goto probe_epilogue;";
+
+  o->newline(-1) << "if (unlikely (atomic_inc_return (&c->busy) != 1)) {";
+
+  o->newline(1) << "if (atomic_inc_return (& skipped_count) > MAXSKIPPED) {";
+  o->newline(1) << "atomic_set (& session_state, STAP_SESSION_ERROR);";
+  // NB: We don't assume that we can safely call stp_error etc. in such
+  // a reentrant context.  But this is OK:
+  o->newline() << "_stp_exit ();";
+  o->newline(-1) << "}";
+
+  o->newline() << "atomic_dec (& c->busy);";
+  o->newline() << "goto probe_epilogue;";
+  o->newline(-1) << "}";
+  o->newline();
+  o->newline() << "c->last_error = 0;";
+  o->newline() << "c->probe_point = probe_point;";
+  o->newline() << "c->nesting = 0;";
+  o->newline() << "c->regs = 0;";
+  o->newline() << "c->actioncount = 0;";
+}
+
+void
+derived_probe::emit_probe_epilogue (translator_output* o)
+{
+  o->newline() << "if (unlikely (c->last_error && c->last_error[0])) {";
+  o->newline(1) << "if (c->last_stmt != NULL)";
+  o->newline(1) << "_stp_softerror (\"%s near %s\", c->last_error, c->last_stmt);";
+  o->newline(-1) << "else";
+  o->newline(1) << "_stp_softerror (\"%s\", c->last_error);";
+  o->indent(-1);
+  o->newline() << "atomic_inc (& error_count);";
+
+  o->newline() << "if (atomic_read (& error_count) > MAXERRORS) {";
+  o->newline(1) << "atomic_set (& session_state, STAP_SESSION_ERROR);";
+  o->newline() << "_stp_exit ();";
+  o->newline(-1) << "}";
+
+  o->newline(-1) << "}";
+  
+  o->newline() << "atomic_dec (&c->busy);";
+  o->newline(-1) << "probe_epilogue: ;";
+  o->indent(1);
+}
+
+
+
+
+// ------------------------------------------------------------------------
 // begin/end probes are run right during registration / deregistration
 // ------------------------------------------------------------------------
 
@@ -147,40 +204,19 @@ be_derived_probe::emit_probe_entries (translator_output* o, unsigned j)
 
       // While begin/end probes are executed single-threaded, we
       // still code defensively and use a per-cpu context.
-      o->newline(1) << "struct context* c = per_cpu_ptr (contexts, smp_processor_id());";
+      o->indent(1);
       o->newline() << "const char* probe_point = "
-		   << lex_cast_qstring(*l) << ";";
-
-      // A precondition for running a probe handler is that we're in STARTING
-      // or STOPPING state (not ERROR), and that no one else is already using
-      // this context.
-      o->newline() << "if (atomic_read (&session_state) != ";
-      if (begin) o->line() << "STAP_SESSION_STARTING)";
-      else o->line() << "STAP_SESSION_STOPPING)";
-      o->newline(1) << "return;";
-      o->newline(-1) << "if (atomic_inc_return (&c->busy) != 1) {";
-      o->newline(1) << "_stp_warn (\"probe reentrancy (%s vs %s)\\n\", "
-		    << "c->probe_point, probe_point);";
-      o->newline() << "atomic_set (& session_state, STAP_SESSION_ERROR);";
-      o->newline() << "atomic_dec (&c->busy);";
-      o->newline() << "return;";
-      o->newline(-1) << "}";
-      o->newline();
-      o->newline() << "c->last_error = 0;";
-      o->newline() << "c->probe_point = probe_point;";
-      o->newline() << "c->nesting = 0;";
-      o->newline() << "c->regs = 0;";
-      o->newline() << "c->actioncount = 0;";
+                   << lex_cast_qstring(*l) << ";";
+      emit_probe_prologue (o,
+                           (begin ?
+                            "STAP_SESSION_STARTING" :
+                            "STAP_SESSION_STOPPING"));
 
       // NB: locals are initialized by probe function itself
       o->newline() << "probe_" << j << " (c);";
 
-      o->newline() << "if (c->last_error && c->last_error[0]) {";
-      o->newline(1) << "_stp_error (\"%s near %s\", c->last_error, c->last_stmt);";
-      o->newline() << "atomic_set (& session_state, STAP_SESSION_ERROR);";
-      o->newline(-1) << "}";
+      emit_probe_epilogue (o);
 
-      o->newline() << "atomic_dec (&c->busy);";
       o->newline(-1) << "}" << endl;
     }
 }
@@ -2936,12 +2972,24 @@ dwarf_derived_probe::emit_deregistrations (translator_output* o, unsigned proben
     {
       o->newline() << "#ifdef ARCH_SUPPORTS_KRETPROBES";
       o->newline() << "unregister_kretprobe (&(" << probe_name << "));";
+      o->newline() << "atomic_add ("
+                   << probe_name << ".kp.nmissed,"
+                   << "& skipped_count);";
+      o->newline() << "atomic_add ("
+                   << probe_name << ".nmissed,"
+                   << "& skipped_count);";
       o->newline() << "#else";
       o->newline() << ";";
       o->newline() << "#endif";
     }
   else
-    o->newline() << "unregister_kprobe (&(" << probe_name << "));";
+    {
+      o->newline() << "unregister_kprobe (&(" << probe_name << "));";
+      o->newline() << "atomic_add ("
+                   << probe_name << ".nmissed,"
+                   << "& skipped_count);";
+    }
+
   o->indent(-1);
   o->newline(-1) << "}";
 }
@@ -3053,7 +3101,7 @@ dwarf_derived_probe::emit_probe_entries (translator_output* o,
   else
     o->line() << "struct kprobe *probe_instance";
   o->line() << ", struct pt_regs *regs) {";
-  o->newline(1) << "struct context* c = per_cpu_ptr (contexts, smp_processor_id());";
+  o->indent(1);
 
   // Calculate the name of the current probe by finding its index in the probe array.
   if (has_return)
@@ -3064,35 +3112,14 @@ dwarf_derived_probe::emit_probe_entries (translator_output* o,
     o->newline() << "const char* probe_point = "
 		 << string_array
 		 << "[ (probe_instance - &(" << probe_array << "[0]))];";
-
-  // A precondition for running a probe handler is that we're in RUNNING
-  // state (not ERROR), and that no one else is already using this context.
-  o->newline() << "if (atomic_read (&session_state) != STAP_SESSION_RUNNING)";
-  o->newline(1) << "return 0;";
-  o->newline(-1) << "if (atomic_inc_return (&c->busy) != 1) {";
-  o->newline(1) << "_stp_warn (\"probe reentrancy (%s vs %s)\\n\", "
-		    << "c->probe_point, probe_point);";
-  o->newline() << "atomic_set (& session_state, STAP_SESSION_ERROR);";
-  o->newline() << "atomic_dec (&c->busy);";
-  o->newline() << "return 0;";
-  o->newline(-1) << "}";
-  o->newline();
-
-  o->newline() << "c->last_error = 0;";
-  o->newline() << "c->probe_point = probe_point;";
-  o->newline() << "c->nesting = 0;";
+  emit_probe_prologue (o, "STAP_SESSION_RUNNING");
   o->newline() << "c->regs = regs;";
-  o->newline() << "c->actioncount = 0;";
 
   // NB: locals are initialized by probe function itself
   o->newline() << "probe_" << probenum << " (c);";
 
-  o->newline() << "if (c->last_error && c->last_error[0]) {";
-  o->newline(1) << "_stp_error (\"%s near %s\", c->last_error, c->last_stmt);";
-  o->newline() << "atomic_set (& session_state, STAP_SESSION_ERROR);";
-  o->newline(-1) << "}";
+  emit_probe_epilogue (o);
 
-  o->newline() << "atomic_dec (& c->busy);";
   o->newline() << "return 0;";
   o->newline(-1) << "}" << endl;
   if (has_return)
@@ -3244,26 +3271,12 @@ timer_derived_probe::emit_probe_entries (translator_output* o, unsigned j)
   o->newline() << "static struct timer_list timer_" << j << ";";
 
   o->newline() << "void enter_" << j << " (unsigned long val) {";
-  o->newline(1) << "struct context* c = per_cpu_ptr (contexts, smp_processor_id());";
+  o->indent(1);
   o->newline() << "const char* probe_point = "
 	       << lex_cast_qstring(*locations[0]) << ";";
-  o->newline() << "(void) val;";
-
-  // A precondition for running a probe handler is that we're in
-  // RUNNING state (not ERROR), and that no one else is already using
-  // this context.
-  o->newline() << "if (atomic_read (&session_state) != STAP_SESSION_RUNNING)";
-  o->newline(1) << "return;";
-
-  o->newline(-1) << "if (atomic_inc_return (&c->busy) != 1) {";
-  o->newline(1) << "_stp_warn (\"probe reentrancy (%s vs %s)\\n\", "
-		<< "c->probe_point, probe_point);";
-  o->newline() << "atomic_set (& session_state, STAP_SESSION_ERROR);";
-  o->newline() << "atomic_dec (&c->busy);";
-  o->newline() << "return;";
-  o->newline(-1) << "}";
-  o->newline();
+  emit_probe_prologue (o, "STAP_SESSION_RUNNING");
 
+  o->newline() << "(void) val;";
   o->newline() << "mod_timer (& timer_" << j << ", jiffies + ";
   if (time_is_msecs)
     o->line() << "msecs_to_jiffies(";
@@ -3274,21 +3287,10 @@ timer_derived_probe::emit_probe_entries (translator_output* o, unsigned j)
     o->line() << ")";
   o->line() << ");";
 
-  o->newline() << "c->probe_point = probe_point;";
-  o->newline() << "c->last_error = 0;";
-  o->newline() << "c->nesting = 0;";
-  o->newline() << "c->regs = 0;";
-  o->newline() << "c->actioncount = 0;";
-
   // NB: locals are initialized by probe function itself
   o->newline() << "probe_" << j << " (c);";
 
-  o->newline() << "if (c->last_error && c->last_error[0]) {";
-  o->newline(1) << "_stp_error (\"%s near %s\", c->last_error, c->last_stmt);";
-  o->newline() << "atomic_set (& session_state, STAP_SESSION_ERROR);";
-  o->newline(-1) << "}";
-
-  o->newline() << "atomic_dec (&c->busy);";
+  emit_probe_epilogue (o);
   o->newline(-1) << "}" << endl;
 }
 
@@ -3394,45 +3396,19 @@ profile_derived_probe::emit_probe_entries (translator_output* o, unsigned j)
     o->newline() << "int enter_" << j << " (struct pt_regs *regs) {";
   }
 
-  o->newline(1) << "struct context* c = per_cpu_ptr (contexts, smp_processor_id());";
+  o->indent(1);
   o->newline() << "const char* probe_point = "
 	       << lex_cast_qstring(*locations[0]) << ";";
+  emit_probe_prologue (o, "STAP_SESSION_RUNNING");
 
   if (using_rpn) {
     o->newline() << "(void) self;";
     o->newline() << "(void) val;";
   }
 
-  // A precondition for running a probe handler is that we're in
-  // RUNNING state (not ERROR), and that no one else is already using
-  // this context.
-  o->newline() << "if (atomic_read (&session_state) != STAP_SESSION_RUNNING)";
-  o->newline(1) << "return 0;";
-
-  o->newline(-1) << "if (atomic_inc_return (&c->busy) != 1) {";
-  o->newline(1) << "_stp_warn (\"probe reentrancy (%s vs %s)\\n\", "
-		<< "c->probe_point, probe_point);";
-  o->newline() << "atomic_set (& session_state, STAP_SESSION_ERROR);";
-  o->newline() << "atomic_dec (&c->busy);";
-  o->newline() << "return 0;";
-  o->newline(-1) << "}";
-  o->newline();
-
-  o->newline() << "c->probe_point = probe_point;";
-  o->newline() << "c->last_error = 0;";
-  o->newline() << "c->nesting = 0;";
-  o->newline() << "c->regs = regs;";
-  o->newline() << "c->actioncount = 0;";
-
-  // NB: locals are initialized by probe function itself
   o->newline() << "probe_" << j << " (c);";
 
-  o->newline() << "if (c->last_error && c->last_error[0]) {";
-  o->newline(1) << "_stp_error (\"%s near %s\", c->last_error, c->last_stmt);";
-  o->newline() << "atomic_set (& session_state, STAP_SESSION_ERROR);";
-  o->newline(-1) << "}";
-
-  o->newline() << "atomic_dec (&c->busy);";
+  emit_probe_epilogue (o);
   o->newline() << "return 0;";
   o->newline(-1) << "}" << endl;
 }
diff --git a/translate.cxx b/translate.cxx
index bda28e8b..78788de9 100644
--- a/translate.cxx
+++ b/translate.cxx
@@ -1,5 +1,5 @@
 // translation pass
-// Copyright (C) 2005 Red Hat Inc.
+// Copyright (C) 2005, 2006 Red Hat Inc.
 // Copyright (C) 2005 Intel Corporation
 //
 // This file is part of systemtap, and is free software.  You can
@@ -444,11 +444,10 @@ struct varlock
 	c.o->newline() << "{";
 	c.o->newline(1) << "unsigned trylock_count = 0;";
 	c.o->newline() << "while ("
-		       << "!(write_trylock (& " << v << "_lock))"
-		       << " && "
-		       << "(trylock_count++ < MAXTRYLOCK)"
-		       << ") ; /* spin */";
-	c.o->newline() << "if (unlikely (trylock_count >= MAXTRYLOCK)) {";
+		       << "!(write_trylock (& " << v << "_lock)) &&";
+        c.o->newline(1) << "(trylock_count++ < MAXTRYLOCK)"
+		       << ") ndelay (TRYLOCKDELAY); /* spin */";
+	c.o->newline(-1) << "if (unlikely (trylock_count >= MAXTRYLOCK)) {";
 	c.o->newline(1) << "c->last_error = \"locking timeout over variable "
 			<< v << "\";";
 	c.o->newline() << "goto " << post_unlock_label << ";";
@@ -820,6 +819,8 @@ c_unparser::emit_common_header ()
   o->newline() << "#define STAP_SESSION_STOPPING 3";
   o->newline() << "#define STAP_SESSION_STOPPED 4";
   o->newline() << "atomic_t session_state = ATOMIC_INIT (STAP_SESSION_STARTING);";
+  o->newline() << "atomic_t error_count = ATOMIC_INIT (0);";
+  o->newline() << "atomic_t skipped_count = ATOMIC_INIT (0);";
   o->newline();
   o->newline() << "struct context {";
   o->newline(1) << "atomic_t busy;";
@@ -942,7 +943,7 @@ void
 c_unparser::emit_functionsig (functiondecl* v)
 {
   o->newline() << "static void function_" << v->name
-	       << " (struct context *c);";
+	       << " (struct context * __restrict__ c);";
 }
 
 
@@ -1101,6 +1102,15 @@ c_unparser::emit_module_exit ()
 
   o->newline() << "free_percpu (contexts);";
 
+  // print final error/reentrancy counts if non-zero
+  o->newline() << "if (atomic_read (& skipped_count) || "
+               << "atomic_read (& error_count))";
+  o->newline(1) << "_stp_warn (\"Number of errors: %d, "
+                << "skipped probes: %d\\n\", "
+                << "(int) atomic_read (& error_count), "
+                << "(int) atomic_read (& skipped_count));";
+  o->indent(-1);
+
   o->newline(-1) << "}" << endl;
 }
 
@@ -1109,7 +1119,7 @@ void
 c_unparser::emit_function (functiondecl* v)
 {
   o->newline() << "void function_" << c_varname (v->name)
-            << " (struct context* c) {";
+            << " (struct context* __restrict__ c) {";
   o->indent(1);
   this->current_probe = 0;
   this->current_probenum = 0;
@@ -1160,8 +1170,8 @@ c_unparser::emit_function (functiondecl* v)
 void
 c_unparser::emit_probe (derived_probe* v, unsigned i)
 {
-  o->newline() << "static void probe_" << i << " (struct context *c);";
-  o->newline() << "void probe_" << i << " (struct context *c) {";
+  // o->newline() << "static void probe_" << i << " (struct context *c);";
+  o->newline() << "static void probe_" << i << " (struct context * __restrict__ c) {";
   o->indent(1);
 
   // initialize frame pointer
@@ -1667,6 +1677,7 @@ c_unparser::visit_statement (statement *s, unsigned actions)
   if (actions > 0)
     {
       o->newline() << "c->actioncount += " << actions << ";";
+      // XXX: This check is inserted too frequently.
       o->newline() << "if (unlikely (c->actioncount > MAXACTION)) {";
       o->newline(1) << "c->last_error = \"MAXACTION exceeded\";";
       o->newline() << "goto " << outlabel << ";";
@@ -3437,15 +3448,24 @@ translate_pass (systemtap_session& s)
       s.op->newline() << "#ifndef MAXSTRINGLEN";
       s.op->newline() << "#define MAXSTRINGLEN 128";
       s.op->newline() << "#endif";
-      s.op->newline() << "#ifndef MAXTRYLOCK";
-      s.op->newline() << "#define MAXTRYLOCK 20";
-      s.op->newline() << "#endif";
       s.op->newline() << "#ifndef MAXACTION";
       s.op->newline() << "#define MAXACTION 1000";
       s.op->newline() << "#endif";
+      s.op->newline() << "#ifndef MAXTRYLOCK";
+      s.op->newline() << "#define MAXTRYLOCK MAXACTION";
+      s.op->newline() << "#endif";
+      s.op->newline() << "#ifndef TRYLOCKDELAY";
+      s.op->newline() << "#define TRYLOCKDELAY 100";
+      s.op->newline() << "#endif";
       s.op->newline() << "#ifndef MAXMAPENTRIES";
       s.op->newline() << "#define MAXMAPENTRIES 2048";
       s.op->newline() << "#endif";
+      s.op->newline() << "#ifndef MAXERRORS";
+      s.op->newline() << "#define MAXERRORS 10";
+      s.op->newline() << "#endif";
+      s.op->newline() << "#ifndef MAXSKIPPED";
+      s.op->newline() << "#define MAXSKIPPED 100";
+      s.op->newline() << "#endif";
 
       // impedance mismatch
       s.op->newline() << "#define STP_STRING_SIZE MAXSTRINGLEN";
@@ -3463,6 +3483,7 @@ translate_pass (systemtap_session& s)
       s.op->newline() << "#include \"regs.c\"";
       s.op->newline() << "#include <linux/string.h>";
       s.op->newline() << "#include <linux/timer.h>";
+      s.op->newline() << "#include <linux/delay.h>";
       s.op->newline() << "#include <linux/profile.h>";
       s.op->newline() << "#endif";
       s.op->newline() << "#include \"loc2c-runtime.h\" ";