X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Fcommon%2Fust-consumer%2Fust-consumer.c;h=2b55fd4637ead2b056fcafecc47ef5504d7c5df5;hb=6e7423591c5edde632d79ff52ba449d99da8eb14;hp=113682384ae44d829d03af00b1378d25687a4a39;hpb=87dc6a9c2c936cf4386043083412c695a914cb36;p=lttng-tools.git

diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index 113682384..2b55fd463 100644
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -2,19 +2,18 @@
  * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; only version 2
- * of the License.
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2 only,
+ * as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
 #define _GNU_SOURCE
@@ -43,9 +42,9 @@ extern volatile int consumer_quit;
 /*
  * Mmap the ring buffer, read it and write the data to the tracefile.
  *
- * Returns the number of bytes written
+ * Returns the number of bytes written, else negative value on error.
  */
-int lttng_ustconsumer_on_read_subbuffer_mmap(
+ssize_t lttng_ustconsumer_on_read_subbuffer_mmap(
 		struct lttng_consumer_local_data *ctx,
 		struct lttng_consumer_stream *stream, unsigned long len)
 {
@@ -59,7 +58,7 @@ int lttng_ustconsumer_on_read_subbuffer_mmap(
 		stream->buf, &mmap_offset);
 	if (ret != 0) {
 		errno = -ret;
-		perror("ustctl_get_mmap_read_offset");
+		PERROR("ustctl_get_mmap_read_offset");
 		goto end;
 	}
 	while (len > 0) {
@@ -68,7 +67,7 @@ int lttng_ustconsumer_on_read_subbuffer_mmap(
 			len = 0;
 		} else if (ret < 0) {
 			errno = -ret;
-			perror("Error in file write");
+			PERROR("Error in file write");
 			goto end;
 		}
 		/* This won't block, but will start writeout asynchronously */
@@ -90,7 +89,7 @@ end:
  *
  * Returns the number of bytes spliced.
  */
-int lttng_ustconsumer_on_read_subbuffer_splice(
+ssize_t lttng_ustconsumer_on_read_subbuffer_splice(
 		struct lttng_consumer_local_data *ctx,
 		struct lttng_consumer_stream *stream, unsigned long len)
 {
@@ -110,7 +109,7 @@ int lttng_ustconsumer_take_snapshot(struct lttng_consumer_local_data *ctx,
 	ret = ustctl_snapshot(stream->chan->handle, stream->buf);
 	if (ret != 0) {
 		errno = -ret;
-		perror("Getting sub-buffer snapshot.");
+		PERROR("Getting sub-buffer snapshot.");
 	}
 
 	return ret;
@@ -132,7 +131,7 @@ int lttng_ustconsumer_get_produced_snapshot(
 			stream->buf, pos);
 	if (ret != 0) {
 		errno = -ret;
-		perror("kernctl_snapshot_get_produced");
+		PERROR("kernctl_snapshot_get_produced");
 	}
 
 	return ret;
@@ -258,11 +257,20 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 		break;
 	}
 end:
-	/* signal the poll thread */
-	ret = write(ctx->consumer_poll_pipe[1], "4", 1);
-	if (ret < 0) {
-		perror("write consumer poll");
-	}
+	/*
+	 * Wake-up the other end by writing a null byte in the pipe
+	 * (non-blocking). Important note: Because writing into the
+	 * pipe is non-blocking (and therefore we allow dropping wakeup
+	 * data, as long as there is wakeup data present in the pipe
+	 * buffer to wake up the other end), the other end should
+	 * perform the following sequence for waiting:
+	 * 1) empty the pipe (reads).
+	 * 2) perform update operation.
+	 * 3) wait on the pipe (poll).
+	 */
+	do {
+		ret = write(ctx->consumer_poll_pipe[1], "", 1);
+	} while (ret == -1UL && errno == EINTR);
 end_nosignal:
 	return 0;
 }
@@ -401,7 +409,7 @@ int lttng_ustconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
 				stream->uid, stream->gid);
 		if (ret < 0) {
 			ERR("Opening %s", stream->path_name);
-			perror("open");
+			PERROR("open");
 			goto error;
 		}
 		stream->out_fd = ret;