From: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Date: Mon, 5 Feb 2018 23:19:00 +0000 (-0500)
Subject: Fix: add-context cannot be performed after a session has been started
X-Git-Tag: v2.11.0-rc1~389
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=9a699f7bb912d287630c8940459069a4b04d2399

Fix: add-context cannot be performed after a session has been started

The following scenario lead to a corrupted trace/metadata layout problem:
  - lttng create test
  - lttng enable-channel -u test
  - lttng enable-event -u -a -c test
  - lttng start
  - ./instrumented-application
  - lttng stop
  - lttng add-context -u -t procname -c test
  - lttng start
  - ./instrumented-application
  - lttng stop
  - lttng view

Babeltrace 1.5.x will fail with:

[error] Unexpected end of packet. Either the trace data stream is corrupted or metadata description does not match data layout.
[error] Reading event failed.
Error printing trace.

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index 67b2e77f4..1a3c22a6c 100644
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -1654,6 +1654,16 @@ int cmd_add_context(struct ltt_session *session, enum lttng_domain_type domain,
 	int ret, chan_kern_created = 0, chan_ust_created = 0;
 	char *app_ctx_provider_name = NULL, *app_ctx_name = NULL;
 
+	/*
+	 * Don't try to add a context if the session has been started at
+	 * some point in time before. The tracer does not allow it and would
+	 * result in a corrupted trace.
+	 */
+	if (session->has_been_started) {
+		ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
+		goto end;
+	}
+
 	if (ctx->ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT) {
 		app_ctx_provider_name = ctx->u.app_ctx.provider_name;
 		app_ctx_name = ctx->u.app_ctx.ctx_name;