From: Julien Desfossez <jdesfossez@efficios.com>
Date: Mon, 11 Dec 2017 21:17:48 +0000 (-0500)
Subject: Keep read-only copies of fields from the channel to the stream
X-Git-Tag: v2.11.0-rc1~358
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=d9a2e16ee3abce83801f58473831330aa8a5463b;p=lttng-tools.git

Keep read-only copies of fields from the channel to the stream

In the consumer, we sometimes need to read the channel pathname or
tracefile_size from a stream, but we cannot always access those values
safely. So we now keep a copy of those values when we add or allocate
streams.

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/common/consumer/consumer.c b/src/common/consumer/consumer.c
index 6b920b6b1..2fa65f4d4 100644
--- a/src/common/consumer/consumer.c
+++ b/src/common/consumer/consumer.c
@@ -541,6 +541,16 @@ void consumer_del_stream_for_metadata(struct lttng_consumer_stream *stream)
 	consumer_stream_destroy(stream, metadata_ht);
 }
 
+void consumer_stream_update_channel_attributes(
+		struct lttng_consumer_stream *stream,
+		struct lttng_consumer_channel *channel)
+{
+	stream->channel_read_only_attributes.tracefile_size =
+			channel->tracefile_size;
+	memcpy(stream->channel_read_only_attributes.path, channel->pathname,
+			sizeof(stream->channel_read_only_attributes.path));
+}
+
 struct lttng_consumer_stream *consumer_allocate_stream(uint64_t channel_key,
 		uint64_t stream_key,
 		enum lttng_consumer_stream_state state,
diff --git a/src/common/consumer/consumer.h b/src/common/consumer/consumer.h
index eb2958e20..a7d0ee1a7 100644
--- a/src/common/consumer/consumer.h
+++ b/src/common/consumer/consumer.h
@@ -415,6 +415,17 @@ struct lttng_consumer_stream {
 	pthread_cond_t metadata_rdv;
 	pthread_mutex_t metadata_rdv_lock;
 
+	/*
+	 * Read-only copies of channel values. We cannot safely access the
+	 * channel from a stream, so we need to have a local copy of these
+	 * fields in the stream object. These fields should be removed from
+	 * the stream objects when we introduce refcounting.
+	 */
+	struct {
+		char path[LTTNG_PATH_MAX];
+		uint64_t tracefile_size;
+	} channel_read_only_attributes;
+
 	/* Indicate if the stream still has some data to be read. */
 	unsigned int has_data:1;
 	/*
@@ -662,6 +673,14 @@ void lttng_consumer_cleanup(void);
  */
 int lttng_consumer_poll_socket(struct pollfd *kconsumer_sockpoll);
 
+/*
+ * Copy the fields from the channel that need to be accessed (read-only)
+ * directly from the stream.
+ */
+void consumer_stream_update_channel_attributes(
+		struct lttng_consumer_stream *stream,
+		struct lttng_consumer_channel *channel);
+
 struct lttng_consumer_stream *consumer_allocate_stream(uint64_t channel_key,
 		uint64_t stream_key,
 		enum lttng_consumer_stream_state state,
diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index 103df665a..539d80b0b 100644
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -658,6 +658,8 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
 		new_stream->chan = channel;
 		new_stream->wait_fd = fd;
+		consumer_stream_update_channel_attributes(new_stream,
+				channel);
 		switch (channel->output) {
 		case CONSUMER_CHANNEL_SPLICE:
 			new_stream->output = LTTNG_EVENT_SPLICE;
diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index ec078fb47..00937a44d 100644
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -184,6 +184,7 @@ static struct lttng_consumer_stream *allocate_stream(int cpu, int key,
 		goto error;
 	}
 
+	consumer_stream_update_channel_attributes(stream, channel);
 	stream->chan = channel;
 
 error: