[lttng-dev] [PATCH lttng-tools 1/2] Fix: add-context cannot be performed after a session has been started

[Jérémie Galarneau]

Merged with a minor fix in master, stable-2.10, and stable-2.9.
I have also tweaked the documentation patch following comments from
Philippe Proulx.

Thanks!
Jérémie

On 5 February 2018 at 18:19, Jonathan Rajotte
<jonathan.rajotte-julien at efficios.com> wrote:
> 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 at efficios.com>
> ---
>  src/bin/lttng-sessiond/cmd.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
> index a295059..1a60ce3 100644
> --- a/src/bin/lttng-sessiond/cmd.c
> +++ b/src/bin/lttng-sessiond/cmd.c
> @@ -1650,6 +1650,17 @@ 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;
> --
> 2.7.4
>



-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com