On Fri, Dec 12, 2014 at 1:36 PM, Nathan Lynch <[email protected]> wrote: > By accident I attempted to build lttng-tools stable-2.6 branch > against current lttng-ust master, and got: > > trace-ust.c: In function 'trace_ust_create_event': > trace-ust.c:430:11: error: 'struct lttng_ust_event' has no member named > 'disabled' > lue->attr.disabled = 1; > ^ > I found the commit below, which seems to indicate that this may be > anticipated/intentional, but I figured I'd raise the issue in case > it's not. Breaking source compatibility with lttng-tools doesn't > seem like a big deal, but does the removal of the 'disabled' field in > lttng-ust/master present a problem for other users of the library?
It's not a problem for instrumented applications as this is strictly a sessiond <-> UST communication change. Regards, Jérémie > > > commit 3a4009667b330f62fc4d6100ead0bcfd5f5526d6 > Author: Mathieu Desnoyers <[email protected]> > Date: Wed Nov 12 18:18:32 2014 -0500 > > Fix: filter attach vs event enable race > > In order to correctly handle the use-case where events are enabled > _after_ trace is started, and _after_ applications are already being > traced, the event should be created in a "disabled" state, so that it > does not trace events until its filter is attached. > > This fix needs to be done both in lttng-tools and lttng-ust. In order to > keep ABI compatibility between tools and ust within a stable release > cycle, we introduce a new "disabled" within struct lttng_ust_event > padding (previously zeroed). Newer LTTng-UST checks this flag, and > fallback on the old racy behavior (enabling the event on creation) if it > is unset. > > Therefore, old session daemon works with newer lttng-ust of the same > stable release, and vice-versa. However, building lttng-tools requires > an upgraded lttng-ust, which contains the communication protocol with > the new "disabled" field. > > This patch should be backported to stable-2.4, stable-2.5, stable-2.6 > branches. > > > _______________________________________________ > lttng-dev mailing list > [email protected] > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Jérémie Galarneau EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
