Fixed race-condition/deadlock problems in the dialog/user agent layer

all the way up to PJSUA-API:
- standardized locking order: dialog then user agent, and dialog then PJSUA
- any threads that attempt to acquire mutexes in different order than
  above MUST employ retry mechanism (for an example, see acquire_call() in
  pjsua_call.c). This retry mechanism has also been used in the UA layer
  (sip_ua_layer.c) since it needs to lock user agent layer first before
  the dialog.
- introduced pjsip_dlg_try_inc_lock() and PJSUA_TRY_LOCK() to accomodate
  above.
- pjsua tested on Quad Xeon with 4 threads and 200 cps, so far so good.



git-svn-id: http://svn.pjsip.org/repos/pjproject/trunk@729 74dad513-b988-da41-8d7b-12977e46ad98

3 files changed, 15 insertions, 21 deletions

diff --git a/pjsip/include/pjsip/sip_dialog.h b/pjsip/include/pjsip/sip_dialog.h
index 191196a5..b4d2a1ac 100644
--- a/pjsip/include/pjsip/sip_dialog.h
+++ b/pjsip/include/pjsip/sip_dialog.h
@@ -356,6 +356,16 @@ PJ_DECL(void*) pjsip_dlg_get_mod_data( pjsip_dialog *dlg,
 PJ_DECL(void) pjsip_dlg_inc_lock( pjsip_dialog *dlg );
 
 /**
+ * Try to acquire dialog's lock, but return immediately if lock can not
+ * be acquired.
+ *
+ * @param dlg		    The dialog.
+ *
+ * @return		    PJ_SUCCESS if lock has been acquired.
+ */
+PJ_DECL(pj_status_t) pjsip_dlg_try_inc_lock( pjsip_dialog *dlg );
+
+/**
  * Unlock dialog and decrement temporary session counter. After this function
  * is called, dialog may be destroyed.
  *
diff --git a/pjsip/include/pjsip/sip_ua_layer.h b/pjsip/include/pjsip/sip_ua_layer.h
index 08e692ca..c4e2d7c7 100644
--- a/pjsip/include/pjsip/sip_ua_layer.h
+++ b/pjsip/include/pjsip/sip_ua_layer.h
@@ -81,24 +81,6 @@ PJ_DECL(pjsip_user_agent*) pjsip_ua_instance(void);
 
 
 /**
- * Lock the dialog's hash table. This function is normally called by
- * dialog code only.
- *
- * @return		PJ_SUCCESS on success or the appropriate error code.
- */
-PJ_DECL(pj_status_t) pjsip_ua_lock_dlg_table(void);
-
-
-/**
- * Unlock the dialog's hash table. This function is normally called by
- * dialog code only.
- *
- * @return		PJ_SUCCESS on success or the appropriate error code.
- */
-PJ_DECL(pj_status_t) pjsip_ua_unlock_dlg_table(void);
-
-
-/**
  * Destroy the user agent layer.
  *
  * @return		PJ_SUCCESS on success.
diff --git a/pjsip/include/pjsua-lib/pjsua_internal.h b/pjsip/include/pjsua-lib/pjsua_internal.h
index 8b1002b4..10e76635 100644
--- a/pjsip/include/pjsua-lib/pjsua_internal.h
+++ b/pjsip/include/pjsua-lib/pjsua_internal.h
@@ -257,11 +257,13 @@ PJ_INLINE(pjsua_im_data*) pjsua_im_data_dup(pj_pool_t *pool,
 }
 
 
-#if 0
-#define PJSUA_LOCK()	    pj_mutex_lock(pjsua_var.mutex);
-#define PJSUA_UNLOCK()	    pj_mutex_unlock(pjsua_var.mutex);
+#if 1
+#define PJSUA_LOCK()	    pj_mutex_lock(pjsua_var.mutex)
+#define PJSUA_TRY_LOCK()    pj_mutex_trylock(pjsua_var.mutex)
+#define PJSUA_UNLOCK()	    pj_mutex_unlock(pjsua_var.mutex)
 #else
 #define PJSUA_LOCK()
+#define PJSUA_TRY_LOCK()    PJ_SUCCESS
 #define PJSUA_UNLOCK()
 #endif