X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fcommon%2Fkernel-consumer%2Fkernel-consumer.c;h=bbc31f8e3be14bdb3927c87a1aabb40e28e777b5;hp=9abee1de8ad5d3bb01efdf2b04ada6270811de18;hb=04fdd819f0eebfd15a4196a9ca98e826352a9b4f;hpb=d14d33bf091e72b23b1f90ea18a0a01bed098b76

diff --git a/src/common/kernel-consumer/kernel-consumer.c b/src/common/kernel-consumer/kernel-consumer.c
index 9abee1de8..bbc31f8e3 100644
--- a/src/common/kernel-consumer/kernel-consumer.c
+++ b/src/common/kernel-consumer/kernel-consumer.c
@@ -295,11 +295,20 @@ int lttng_kconsumer_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;
 }