[lttng-dev] [PATCH lttng-tools 03/10] Fix: kernel tracing: flush after stop

[Jérémie Galarneau]

Good catch, merged!

Thanks,
Jérémie

On Wed, May 18, 2016 at 2:04 PM, Mathieu Desnoyers
<mathieu.desnoyers at efficios.com> wrote:
> We should flush the last packet after stop, not before. Otherwise, we
> may end up with events written immediately after the flush, which
> defeats the purpose of flushing.
>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> ---
>  src/bin/lttng-sessiond/cmd.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
> index 16d8ba2..d57edcd 100644
> --- a/src/bin/lttng-sessiond/cmd.c
> +++ b/src/bin/lttng-sessiond/cmd.c
> @@ -2437,7 +2437,15 @@ int cmd_stop_trace(struct ltt_session *session)
>         if (ksession && ksession->active) {
>                 DBG("Stop kernel tracing");
>
> -               /* Flush metadata if exist */
> +               ret = kernel_stop_session(ksession);
> +               if (ret < 0) {
> +                       ret = LTTNG_ERR_KERN_STOP_FAIL;
> +                       goto error;
> +               }
> +
> +               kernel_wait_quiescent(kernel_tracer_fd);
> +
> +               /* Flush metadata after stopping (if exists) */
>                 if (ksession->metadata_stream_fd >= 0) {
>                         ret = kernel_metadata_flush_buffer(ksession->metadata_stream_fd);
>                         if (ret < 0) {
> @@ -2445,7 +2453,7 @@ int cmd_stop_trace(struct ltt_session *session)
>                         }
>                 }
>
> -               /* Flush all buffers before stopping */
> +               /* Flush all buffers after stopping */
>                 cds_list_for_each_entry(kchan, &ksession->channel_list.head, list) {
>                         ret = kernel_flush_buffer(kchan);
>                         if (ret < 0) {
> @@ -2453,14 +2461,6 @@ int cmd_stop_trace(struct ltt_session *session)
>                         }
>                 }
>
> -               ret = kernel_stop_session(ksession);
> -               if (ret < 0) {
> -                       ret = LTTNG_ERR_KERN_STOP_FAIL;
> -                       goto error;
> -               }
> -
> -               kernel_wait_quiescent(kernel_tracer_fd);
> -
>                 ksession->active = 0;
>         }
>
> --
> 2.1.4
>



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