[PATCH 5/5] utils/rpctrace: fix output so that replies can be attributed to requests

[Justus Winter]

Currently, it is impossible to properly attribute response messages to
requests.  Even though rpctrace is single-threaded, its tracee may
not.  Or there might be more than one tracee.  In any such case it is
not guaranteed that the reply message we just processed is for the
request we just printed.  Fix this by printing ellipsis with the port
name, so that reply messages can be properly attributed:

task129(pid3312)->mach_port_allocate (3) ...134
task129(pid3312)->mach_port_deallocate (pn{  1}) ...160
134... = 0 pn{ 30}
160... = 0

* utils/rpctrace.c (last_reply_port): New variable.
(print_ellipsis): New function.
(print_request_header): Optionally print ellipsis and update
last_reply_port.
(print_reply_header): Likewise.
---
 utils/rpctrace.c |   28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/utils/rpctrace.c b/utils/rpctrace.c
index f6e255b..9605089 100644
--- a/utils/rpctrace.c
+++ b/utils/rpctrace.c
@@ -1,7 +1,7 @@
 /* Trace RPCs sent to selected ports
 
-   Copyright (C) 1998, 1999, 2001, 2002, 2003, 2005, 2006, 2009, 2011
-   Free Software Foundation, Inc.
+   Copyright (C) 1998, 1999, 2001, 2002, 2003, 2005, 2006, 2009, 2011,
+   2013 Free Software Foundation, Inc.
 
    This file is part of the GNU Hurd.
 
@@ -1486,10 +1486,27 @@ static const char *const msg_types[] =
 };
 #endif
 
+/* We keep track of the last reply port used in a request we print to
+   ostream.  This way we can end incomplete requests with an ellipsis
+   and the name of the reply port.  When the reply finally arrives, we
+   start a new line with that port name and an ellipsis, making it
+   easy to match it to the associated request.  */
+static mach_port_t last_reply_port;
+
+/* Print an ellipsis if necessary.  */
+static void
+print_ellipsis (void)
+{
+  if (MACH_PORT_VALID (last_reply_port))
+    fprintf (ostream, " ...%u\n", (unsigned int) last_reply_port);
+}
+
 static void
 print_request_header (struct sender_info *receiver, mach_msg_header_t *msg)
 {
   const char *msgname = msgid_name (msg->msgh_id);
+  print_ellipsis ();
+  last_reply_port = msg->msgh_local_port;
 
   if (TRACED_INFO (receiver)->name != 0)
     fprintf (ostream, "%4s->", TRACED_INFO (receiver)->name);
@@ -1507,6 +1524,13 @@ static void
 print_reply_header (struct send_once_info *info, mig_reply_header_t *reply,
                    struct req_info *req)
 {
+  if (last_reply_port != info->pi.pi.port_right)
+    {
+      print_ellipsis ();
+      fprintf (ostream, "%u...", (unsigned int) info->pi.pi.port_right);
+    }
+  last_reply_port = MACH_PORT_NULL;
+
   /* We have printed a partial line for the request message,
      and now we have the corresponding reply.  */
   if (reply->Head.msgh_id == req->req_id + 100)
-- 
1.7.10.4