From 438f9ed26c63bd47c9e1a5cbe52731996f05c3ea Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Mon, 23 Nov 2009 15:53:24 -0500
Subject: [PATCH] Add the abilitity to mark some buffer callbacks as
 never-deferred.

---
 buffer.c                | 48 +++++++++++++++++++++--------------------
 bufferevent.c           |  4 ++--
 include/event2/buffer.h |  3 +++
 3 files changed, 30 insertions(+), 25 deletions(-)

diff --git a/buffer.c b/buffer.c
index 4111a8e4..be9c7ec9 100644
--- a/buffer.c
+++ b/buffer.c
@@ -123,13 +123,6 @@ static int use_mmap = 1;
 /* Mask of all internal-use-only flags. */
 #define EVBUFFER_CB_INTERNAL_FLAGS  0xffff0000
 
-#if 0
-/* Flag set on suspended callbacks. */
-#define EVBUFFER_CB_SUSPENDED          0x00010000
-/* Flag set if we should invoke the callback on wakeup. */
-#define EVBUFFER_CB_CALL_ON_UNSUSPEND  0x00020000
-#endif
-
 /* Flag set if the callback is using the cb_obsolete function pointer  */
 #define EVBUFFER_CB_OBSOLETE           0x00040000
 
@@ -334,11 +327,23 @@ evbuffer_set_parent(struct evbuffer *buf, struct bufferevent *bev)
 }
 
 static void
-evbuffer_run_callbacks(struct evbuffer *buffer)
+evbuffer_run_callbacks(struct evbuffer *buffer, int running_deferred)
 {
 	struct evbuffer_cb_entry *cbent, *next;
         struct evbuffer_cb_info info;
 	size_t new_size;
+	uint32_t mask, masked_val;
+
+	if (running_deferred) {
+		mask = EVBUFFER_CB_NODEFER|EVBUFFER_CB_ENABLED;
+		masked_val = EVBUFFER_CB_ENABLED;
+	} else if (buffer->deferred_cbs) {
+		mask = EVBUFFER_CB_NODEFER|EVBUFFER_CB_ENABLED;
+		masked_val = EVBUFFER_CB_NODEFER|EVBUFFER_CB_ENABLED;
+	} else {
+		mask = EVBUFFER_CB_ENABLED;
+		masked_val = EVBUFFER_CB_ENABLED;
+	}
 
         ASSERT_EVBUFFER_LOCKED(buffer);
 
@@ -362,18 +367,15 @@ evbuffer_run_callbacks(struct evbuffer *buffer)
 		/* Get the 'next' pointer now in case this callback decides
 		 * to remove itself or something. */
 		next = TAILQ_NEXT(cbent, next);
-		if ((cbent->flags & EVBUFFER_CB_ENABLED)) {
-#if 0
-			if ((cbent->flags & EVBUFFER_CB_SUSPENDED))
-				cbent->flags |= EVBUFFER_CB_CALL_ON_UNSUSPEND;
-			else
-#endif
-                        if ((cbent->flags & EVBUFFER_CB_OBSOLETE))
-                                cbent->cb.cb_obsolete(buffer,
-                                        info.orig_size, new_size, cbent->cbarg);
-                        else
-                                cbent->cb.cb_func(buffer, &info, cbent->cbarg);
-		}
+
+		if ((cbent->flags & mask) != masked_val)
+			continue;
+
+		if ((cbent->flags & EVBUFFER_CB_OBSOLETE))
+			cbent->cb.cb_obsolete(buffer,
+			    info.orig_size, new_size, cbent->cbarg);
+		else
+			cbent->cb.cb_func(buffer, &info, cbent->cbarg);
 	}
 }
 
@@ -388,9 +390,9 @@ evbuffer_invoke_callbacks(struct evbuffer *buffer)
 			bufferevent_incref(buffer->parent);
 		EVBUFFER_UNLOCK(buffer);
 		event_deferred_cb_schedule(buffer->cb_queue, &buffer->deferred);
-	} else {
-		evbuffer_run_callbacks(buffer);
 	}
+
+	evbuffer_run_callbacks(buffer, 0);
 }
 
 static void
@@ -403,7 +405,7 @@ evbuffer_deferred_callback(struct deferred_cb *cb, void *arg)
 	 * lock */
 	EVBUFFER_LOCK(buffer);
 	parent = buffer->parent;
-	evbuffer_run_callbacks(buffer);
+	evbuffer_run_callbacks(buffer, 1);
 	_evbuffer_decref_and_unlock(buffer);
 	if (parent)
 		bufferevent_free(parent);
diff --git a/bufferevent.c b/bufferevent.c
index 20b2afb0..2794cff2 100644
--- a/bufferevent.c
+++ b/bufferevent.c
@@ -443,8 +443,8 @@ bufferevent_setwatermark(struct bufferevent *bufev, short events,
 						    bufev);
 			}
 			evbuffer_cb_set_flags(bufev->input,
-					      bufev_private->read_watermarks_cb,
-					      EVBUFFER_CB_ENABLED);
+				      bufev_private->read_watermarks_cb,
+				      EVBUFFER_CB_ENABLED|EVBUFFER_CB_NODEFER);
 
 			if (evbuffer_get_length(bufev->input) > highmark)
 				bufferevent_wm_suspend_read(bufev);
diff --git a/include/event2/buffer.h b/include/event2/buffer.h
index 2a8e8378..0fb6dffd 100644
--- a/include/event2/buffer.h
+++ b/include/event2/buffer.h
@@ -610,6 +610,9 @@ int evbuffer_remove_cb(struct evbuffer *buffer, evbuffer_cb_func cb, void *cbarg
  * should not be invoked. */
 #define EVBUFFER_CB_ENABLED 1
 
+/* Experimental cb flag: "never deferred" */
+#define EVBUFFER_CB_NODEFER 2
+
 /** Change the flags that are set for a callback on a buffer by adding more.
 
     @param buffer the evbuffer that the callback is watching.