X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=lttng-events.c;h=cfe2a3529de33efb0184409d4dbdbd105eb93b8a;hb=3bcb1fb34fc8904413476afd87afbdeab3806e56;hp=5a64f5b2e915950233c695b35540344718c3a78f;hpb=ea53823c42a70a80566a340834e2b00e650406b9;p=lttng-modules.git

diff --git a/lttng-events.c b/lttng-events.c
index 5a64f5b2..cfe2a352 100644
--- a/lttng-events.c
+++ b/lttng-events.c
@@ -1622,7 +1622,7 @@ void lttng_session_lazy_sync_enablers(struct lttng_session *session)
  * was written and a negative value on error.
  */
 int lttng_metadata_output_channel(struct lttng_metadata_stream *stream,
-		struct channel *chan)
+		struct channel *chan, bool *coherent)
 {
 	struct lib_ring_buffer_ctx ctx;
 	int ret = 0;
@@ -1661,6 +1661,7 @@ int lttng_metadata_output_channel(struct lttng_metadata_stream *stream,
 	ret = stream->transport->ops.event_reserve(&ctx, 0);
 	if (ret != 0) {
 		printk(KERN_WARNING "LTTng: Metadata event reservation failed\n");
+		stream->coherent = false;
 		goto end;
 	}
 	stream->transport->ops.event_write(&ctx,
@@ -1668,18 +1669,43 @@ int lttng_metadata_output_channel(struct lttng_metadata_stream *stream,
 			reserve_len);
 	stream->transport->ops.event_commit(&ctx);
 	stream->metadata_in += reserve_len;
+	if (reserve_len < len || stream->metadata_cache->producing != 0)
+		stream->coherent = false;
+	else
+		stream->coherent = true;
 	ret = reserve_len;
 
 end:
+	if (coherent)
+		*coherent = stream->coherent;
 	mutex_unlock(&stream->metadata_cache->lock);
 	return ret;
 }
 
+static
+void lttng_metadata_begin(struct lttng_session *session)
+{
+	mutex_lock(&session->metadata_cache->lock);
+	session->metadata_cache->producing++;
+	mutex_unlock(&session->metadata_cache->lock);
+}
+
+static
+void lttng_metadata_end(struct lttng_session *session)
+{
+	mutex_lock(&session->metadata_cache->lock);
+	WARN_ON_ONCE(!session->metadata_cache->producing);
+	session->metadata_cache->producing--;
+	mutex_unlock(&session->metadata_cache->lock);
+}
+
 /*
  * Write the metadata to the metadata cache.
  * Must be called with sessions_mutex held.
  * The metadata cache lock protects us from concurrent read access from
  * thread outputting metadata content to ring buffer.
+ * The content of the printf is printed as a single atomic metadata
+ * transaction.
  */
 int lttng_metadata_printf(struct lttng_session *session,
 			  const char *fmt, ...)
@@ -1699,6 +1725,7 @@ int lttng_metadata_printf(struct lttng_session *session,
 
 	len = strlen(str);
 	mutex_lock(&session->metadata_cache->lock);
+	session->metadata_cache->producing++;
 	if (session->metadata_cache->metadata_written + len >
 			session->metadata_cache->cache_alloc) {
 		char *tmp_cache_realloc;
@@ -1724,6 +1751,7 @@ int lttng_metadata_printf(struct lttng_session *session,
 			session->metadata_cache->metadata_written,
 			str, len);
 	session->metadata_cache->metadata_written += len;
+	session->metadata_cache->producing--;
 	mutex_unlock(&session->metadata_cache->lock);
 	kfree(str);
 
@@ -1733,6 +1761,7 @@ int lttng_metadata_printf(struct lttng_session *session,
 	return 0;
 
 err:
+	session->metadata_cache->producing--;
 	mutex_unlock(&session->metadata_cache->lock);
 	kfree(str);
 	return -ENOMEM;
@@ -2270,6 +2299,8 @@ int _lttng_fields_metadata_statedump(struct lttng_session *session,
 
 /*
  * Must be called with sessions_mutex held.
+ * The entire event metadata is printed as a single atomic metadata
+ * transaction.
  */
 static
 int _lttng_event_metadata_statedump(struct lttng_session *session,
@@ -2283,6 +2314,8 @@ int _lttng_event_metadata_statedump(struct lttng_session *session,
 	if (chan->channel_type == METADATA_CHANNEL)
 		return 0;
 
+	lttng_metadata_begin(session);
+
 	ret = lttng_metadata_printf(session,
 		"event {\n"
 		"	name = \"%s\";\n"
@@ -2332,12 +2365,15 @@ int _lttng_event_metadata_statedump(struct lttng_session *session,
 
 	event->metadata_dumped = 1;
 end:
+	lttng_metadata_end(session);
 	return ret;
 
 }
 
 /*
  * Must be called with sessions_mutex held.
+ * The entire channel metadata is printed as a single atomic metadata
+ * transaction.
  */
 static
 int _lttng_channel_metadata_statedump(struct lttng_session *session,
@@ -2351,6 +2387,8 @@ int _lttng_channel_metadata_statedump(struct lttng_session *session,
 	if (chan->channel_type == METADATA_CHANNEL)
 		return 0;
 
+	lttng_metadata_begin(session);
+
 	WARN_ON_ONCE(!chan->header_type);
 	ret = lttng_metadata_printf(session,
 		"stream {\n"
@@ -2384,6 +2422,7 @@ int _lttng_channel_metadata_statedump(struct lttng_session *session,
 
 	chan->metadata_dumped = 1;
 end:
+	lttng_metadata_end(session);
 	return ret;
 }
 
@@ -2571,6 +2610,9 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
 
 	if (!READ_ONCE(session->active))
 		return 0;
+
+	lttng_metadata_begin(session);
+
 	if (session->metadata_dumped)
 		goto skip_session;
 
@@ -2743,6 +2785,7 @@ skip_session:
 	}
 	session->metadata_dumped = 1;
 end:
+	lttng_metadata_end(session);
 	return ret;
 }