From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 23 Nov 2010 22:59:20 +0000 (-0500)
Subject: update ltt-events
X-Git-Tag: v2.0-pre1~221
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=e5382b6d90ebe0752f5955a91525f3207f440e18;p=lttng-modules.git

update ltt-events

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/ltt-events.c b/ltt-events.c
index a85b7932..688d7f3b 100644
--- a/ltt-events.c
+++ b/ltt-events.c
@@ -59,6 +59,8 @@ struct ltt_channel *ltt_channel_create(struct ltt_session *session, char *name,
 	struct ltt_channel *chan;
 
 	mutex_lock(&sessions_mutex);
+	if (session->active)
+		goto active;	/* Refuse to add channel to active session */
 	list_for_each_entry(chan, &session->chan, list)
 		if (!strcmp(chan->name, name))
 			goto exist;
@@ -74,6 +76,7 @@ struct ltt_channel *ltt_channel_create(struct ltt_session *session, char *name,
 	return chan;
 
 exist:
+active:
 	mutex_unlock(&sessions_mutex);
 	return NULL;
 }
@@ -87,12 +90,17 @@ int _ltt_channel_destroy(struct ltt_channel *chan)
 	kfree(chan);
 }
 
+/*
+ * Supports event creation while tracing session is active.
+ */
 struct ltt_event *ltt_event_create(struct ltt_channel *chan, char *name,
 				   void *filter)
 {
 	struct ltt_event *event;
 
 	mutex_lock(&sessions_mutex);
+	if (chan->free_event_id == -1UL)
+		goto full;
 	/*
 	 * This is O(n^2) (for each event loop called at event creation).
 	 * Might require a hash if we have lots of events.
@@ -109,15 +117,18 @@ struct ltt_event *ltt_event_create(struct ltt_channel *chan, char *name,
 	strcpy(event->name, name);
 	event->chan = chan;
 	event->filter = filter;
-	event->id = atomic_inc_return(&chan->free_event_id) - 1;
-	/* TODO register to tracepoint */
+	event->id = chan->free_event_id++;
 	mutex_unlock(&sessions_mutex);
+	/* Populate ltt_event structure before tracepoint registration. */
+	smp_wmb();
+	/* TODO register to tracepoint */
 	return event;
 
 error:
 	kmem_cache_free(event);
 cache_error:
 exist:
+full:
 	mutex_unlock(&sessions_mutex);
 	return NULL;
 }
diff --git a/ltt-events.h b/ltt-events.h
index d205cdb0..99edb4b1 100644
--- a/ltt-events.h
+++ b/ltt-events.h
@@ -27,12 +27,13 @@ struct ltt_channel {
 	struct channel *chan;		/* Channel buffers */
 	/* Event ID management */
 	struct ltt_session *session;
-	atomic_t free_event_id;		/* Next event ID to allocate */
+	unsigned int free_event_id;	/* Next event ID to allocate */
 	struct list_head list;		/* Channel list */
 	char name[PATH_MAX];
 };
 
 struct ltt_session {
+	int active;			/* Is trace session active ? */
 	struct list_head chan;		/* Channel list head */
 	struct list_head events;	/* Event list head */
 	struct list_head list;		/* Session list */