X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=src%2Fcommon%2Fust-consumer%2Fust-consumer.c;h=2b55fd4637ead2b056fcafecc47ef5504d7c5df5;hb=5a4b955ed97bb0802977e50f1aa409f0bb4729ec;hp=bfdb7e968fe9aa77ba9ad922e8fb6bf8748f4353;hpb=8cf66a2b6551d770a8aedf1301bcec2270041785;p=lttng-tools.git

diff --git a/src/common/ust-consumer/ust-consumer.c b/src/common/ust-consumer/ust-consumer.c
index bfdb7e968..2b55fd463 100644
--- a/src/common/ust-consumer/ust-consumer.c
+++ b/src/common/ust-consumer/ust-consumer.c
@@ -257,11 +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;
 }