From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 16 Nov 2011 02:01:47 +0000 (-0500)
Subject: UST consumer: fix read on hangup, and UST get subbuf error handling
X-Git-Tag: v2.0-pre15~107
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=effcf122563da70fc22a5dcadf4fce3476035c54

UST consumer: fix read on hangup, and UST get subbuf error handling

This fixes multiple consecutive runs of the "demo" program, where
sometimes one channel would not be saved.

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

diff --git a/liblttng-consumer/lttng-consumer.c b/liblttng-consumer/lttng-consumer.c
index 293d5f808..0d8dd0014 100644
--- a/liblttng-consumer/lttng-consumer.c
+++ b/liblttng-consumer/lttng-consumer.c
@@ -178,7 +178,7 @@ struct lttng_consumer_stream *consumer_allocate_stream(
 	struct lttng_consumer_stream *stream;
 	int ret;
 
-	stream = malloc(sizeof(*stream));
+	stream = zmalloc(sizeof(*stream));
 	if (stream == NULL) {
 		perror("malloc struct lttng_consumer_stream");
 		goto end;
@@ -574,7 +574,7 @@ struct lttng_consumer_local_data *lttng_consumer_create(
 		consumer_data.type == type);
 	consumer_data.type = type;
 
-	ctx = malloc(sizeof(struct lttng_consumer_local_data));
+	ctx = zmalloc(sizeof(struct lttng_consumer_local_data));
 	if (ctx == NULL) {
 		perror("allocating context");
 		goto error;
@@ -760,7 +760,7 @@ void *lttng_consumer_thread_poll_fds(void *data)
 	int tmp2;
 	struct lttng_consumer_local_data *ctx = data;
 
-	local_stream = malloc(sizeof(struct lttng_consumer_stream));
+	local_stream = zmalloc(sizeof(struct lttng_consumer_stream));
 
 	while (1) {
 		high_prio = 0;
@@ -782,7 +782,7 @@ void *lttng_consumer_thread_poll_fds(void *data)
 			}
 
 			/* allocate for all fds + 1 for the consumer_poll_pipe */
-			pollfd = malloc((consumer_data.stream_count + 1) * sizeof(struct pollfd));
+			pollfd = zmalloc((consumer_data.stream_count + 1) * sizeof(struct pollfd));
 			if (pollfd == NULL) {
 				perror("pollfd malloc");
 				pthread_mutex_unlock(&consumer_data.lock);
@@ -790,7 +790,7 @@ void *lttng_consumer_thread_poll_fds(void *data)
 			}
 
 			/* allocate for all fds + 1 for the consumer_poll_pipe */
-			local_stream = malloc((consumer_data.stream_count + 1) *
+			local_stream = zmalloc((consumer_data.stream_count + 1) *
 					sizeof(struct lttng_consumer_stream));
 			if (local_stream == NULL) {
 				perror("local_stream malloc");
@@ -867,12 +867,10 @@ void *lttng_consumer_thread_poll_fds(void *data)
 						pollfd[i].fd);
 					if (!local_stream[i]->hangup_flush_done) {
 						lttng_ustconsumer_on_stream_hangup(local_stream[i]);
-						/* try reading after flush */
-						ret = ctx->on_buffer_ready(local_stream[i], ctx);
-						/* it's ok to have an unavailable sub-buffer */
-						if (ret == EAGAIN) {
-							ret = 0;
-						}
+						/* read after flush */
+						do {
+							ret = ctx->on_buffer_ready(local_stream[i], ctx);
+						} while (ret == EAGAIN);
 					}
 				} else {
 					DBG("Polling fd %d tells it has hung up.", pollfd[i].fd);
diff --git a/liblttng-ustconsumer/lttng-ustconsumer.c b/liblttng-ustconsumer/lttng-ustconsumer.c
index f938d3548..89dbefa36 100644
--- a/liblttng-ustconsumer/lttng-ustconsumer.c
+++ b/liblttng-ustconsumer/lttng-ustconsumer.c
@@ -287,6 +287,7 @@ int lttng_ustconsumer_allocate_channel(struct lttng_consumer_channel *chan)
 void lttng_ustconsumer_on_stream_hangup(struct lttng_consumer_stream *stream)
 {
 	ustctl_flush_buffer(stream->chan->handle, stream->buf, 0);
+	stream->hangup_flush_done = 1;
 }
 
 void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
@@ -343,12 +344,14 @@ int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
 		stream->wait_fd, stream->key);
 
 	/* We can consume the 1 byte written into the wait_fd by UST */
-	do {
-		readlen = read(stream->wait_fd, &dummy, 1);
-	} while (readlen == -1 && errno == -EINTR);
-	if (readlen == -1) {
-		ret = readlen;
-		goto end;
+	if (!stream->hangup_flush_done) {
+		do {
+			readlen = read(stream->wait_fd, &dummy, 1);
+		} while (readlen == -1 && errno == -EINTR);
+		if (readlen == -1) {
+			ret = readlen;
+			goto end;
+		}
 	}
 
 	buf = stream->buf;
@@ -356,7 +359,7 @@ int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
 	/* Get the next subbuffer */
 	err = ustctl_get_next_subbuf(handle, buf);
 	if (err != 0) {
-		ret = errno;
+		ret = -ret;	/* ustctl_get_next_subbuf returns negative, caller expect positive. */
 		/*
 		 * This is a debug message even for single-threaded consumer,
 		 * because poll() have more relaxed criterions than get subbuf,
@@ -370,11 +373,7 @@ int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
 	assert(stream->output == LTTNG_EVENT_MMAP);
 	/* read the used subbuffer size */
 	err = ustctl_get_padded_subbuf_size(handle, buf, &len);
-	if (err != 0) {
-		ret = errno;
-		perror("Getting sub-buffer len failed.");
-		goto end;
-	}
+	assert(err == 0);
 	/* write the subbuffer to the tracefile */
 	ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len);
 	if (ret < 0) {
@@ -385,16 +384,7 @@ int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
 		ERR("Error writing to tracefile");
 	}
 	err = ustctl_put_next_subbuf(handle, buf);
-	if (err != 0) {
-		ret = errno;
-		if (errno == EFAULT) {
-			perror("Error in unreserving sub buffer\n");
-		} else if (errno == EIO) {
-			/* Should never happen with newer LTTng versions */
-			perror("Reader has been pushed by the writer, last sub-buffer corrupted.");
-		}
-		goto end;
-	}
+	assert(err == 0);
 end:
 	return ret;
 }