From 718dadcb900e5a206833f25b40cfbafb4d111c35 Mon Sep 17 00:00:00 2001
From: Simon McVittie <simon.mcvittie@collabora.co.uk>
Date: Fri, 13 May 2011 11:35:03 +0100
Subject: [PATCH 5/7] DBusPendingCall: optionally trace refcount changes

---
 dbus/dbus-pending-call.c |   80 ++++++++++++++++++++++++++++++++++++++++------
 1 files changed, 70 insertions(+), 10 deletions(-)

diff --git a/dbus/dbus-pending-call.c b/dbus/dbus-pending-call.c
index 1e5f0c6..3440ba2 100644
--- a/dbus/dbus-pending-call.c
+++ b/dbus/dbus-pending-call.c
@@ -30,6 +30,7 @@
 #include "dbus-list.h"
 #include "dbus-threads.h"
 #include "dbus-test.h"
+#include "dbus-valgrind-internal.h"
 
 /**
  * @defgroup DBusPendingCallInternals DBusPendingCall implementation details
@@ -79,6 +80,47 @@ struct DBusPendingCall
   unsigned int timeout_added : 1;                 /**< Have added the timeout */
 };
 
+#ifdef DBUS_ENABLE_VERBOSE_MODE
+static void
+_dbus_pending_call_trace_ref (DBusPendingCall *pending_call,
+    int old_refcount,
+    int new_refcount,
+    const char *why)
+{
+  static int enabled = -1;
+
+  if (enabled < 0)
+    {
+      const char *s = _dbus_getenv ("DBUS_PENDING_CALL_TRACE");
+
+      enabled = FALSE;
+
+      if (s && *s)
+        {
+          if (*s == '0')
+            enabled = FALSE;
+          else if (*s == '1')
+            enabled = TRUE;
+          else
+            _dbus_warn ("DBUS_PENDING_CALL_TRACE should be 0 or 1 if set, "
+                "not '%s'", s);
+        }
+    }
+
+  if (enabled)
+    {
+      if (RUNNING_ON_VALGRIND)
+        VALGRIND_PRINTF_BACKTRACE ("DBusPendingCall %p %d -> %d refs (%s)",
+            pending_call, old_refcount, new_refcount, why);
+      else
+        _dbus_verbose ("DBusPendingCall %p %d -> %d refs (%s)",
+            pending_call, old_refcount, new_refcount, why);
+    }
+}
+#else
+#define _dbus_pending_call_trace_ref(p,o,n,w) do {} while (0)
+#endif
+
 static dbus_int32_t notify_user_data_slot = -1;
 
 /**
@@ -138,7 +180,9 @@ _dbus_pending_call_new_unlocked (DBusConnection    *connection,
   _dbus_connection_ref_unlocked (pending->connection);
 
   _dbus_data_slot_list_init (&pending->slot_list);
-  
+
+  _dbus_pending_call_trace_ref (pending, 0, 1, "new_unlocked");
+
   return pending;
 }
 
@@ -373,6 +417,8 @@ _dbus_pending_call_set_timeout_error_unlocked (DBusPendingCall *pending,
 DBusPendingCall *
 _dbus_pending_call_ref_unlocked (DBusPendingCall *pending)
 {
+  _dbus_pending_call_trace_ref (pending, pending->refcount.value,
+      pending->refcount.value + 1, "ref_unlocked");
   pending->refcount.value += 1;
   
   return pending;
@@ -436,6 +482,9 @@ _dbus_pending_call_unref_and_unlock (DBusPendingCall *pending)
   
   _dbus_assert (pending->refcount.value > 0);
 
+  _dbus_pending_call_trace_ref (pending, pending->refcount.value,
+      pending->refcount.value - 1, "unref_and_unlock");
+
   pending->refcount.value -= 1;
   last_unref = pending->refcount.value == 0;
 
@@ -531,21 +580,29 @@ _dbus_pending_call_set_data_unlocked (DBusPendingCall  *pending,
 DBusPendingCall *
 dbus_pending_call_ref (DBusPendingCall *pending)
 {
+  dbus_int32_t old_refcount;
+
   _dbus_return_val_if_fail (pending != NULL, NULL);
 
   /* The connection lock is better than the global
    * lock in the atomic increment fallback
    */
 #ifdef DBUS_HAVE_ATOMIC_INT
-  _dbus_atomic_inc (&pending->refcount);
+  old_refcount = _dbus_atomic_inc (&pending->refcount);
 #else
   CONNECTION_LOCK (pending->connection);
-  _dbus_assert (pending->refcount.value > 0);
+  old_refcount = pending->refcount.value;
+  _dbus_assert (old_refcount > 0);
 
   pending->refcount.value += 1;
   CONNECTION_UNLOCK (pending->connection);
 #endif
-  
+
+  _dbus_pending_call_trace_ref (pending, old_refcount, old_refcount + 1,
+      "ref");
+  /* unused if not verbose */
+  (void) old_refcount;
+
   return pending;
 }
 
@@ -558,7 +615,7 @@ dbus_pending_call_ref (DBusPendingCall *pending)
 void
 dbus_pending_call_unref (DBusPendingCall *pending)
 {
-  dbus_bool_t last_unref;
+  dbus_int32_t old_refcount;
 
   _dbus_return_if_fail (pending != NULL);
 
@@ -566,16 +623,19 @@ dbus_pending_call_unref (DBusPendingCall *pending)
    * int fallback if we lack atomic int decrement
    */
 #ifdef DBUS_HAVE_ATOMIC_INT
-  last_unref = (_dbus_atomic_dec (&pending->refcount) == 1);
+  old_refcount = _dbus_atomic_dec (&pending->refcount);
 #else
   CONNECTION_LOCK (pending->connection);
-  _dbus_assert (pending->refcount.value > 0);
+  old_refcount = pending->refcount.value;
+  _dbus_assert (old_refcount > 0);
   pending->refcount.value -= 1;
-  last_unref = pending->refcount.value == 0;
   CONNECTION_UNLOCK (pending->connection);
 #endif
-  
-  if (last_unref)
+
+  _dbus_pending_call_trace_ref (pending, old_refcount, old_refcount - 1,
+      "unref");
+
+  if (old_refcount == 1)
     _dbus_pending_call_last_unref(pending);
 }
 
-- 
1.7.5.1