[lttng-dev] Event redefinition/re-enablement

[Thibault, Daniel]

----------------------------------------------------------------------
Date: Sun, 16 Mar 2014 00:41:28 -0700
From: Ruslan Uvashev <ruslan.uvashev at gmail.com>

> It seems that event once enabled for a channel cannot be reassigned to another channel.
> If events are immutable will Feature #445 (https://bugs.lttng.org/issues/445)
>  account such situation? Or do we need to update man saying that events
> cannot be redefined?
>
> Command output below.
>
> $ sudo lttng create tst1
> Session tst1 created.
> Traces will be written in /home/rusty/lttng-traces/tst1-20140315-173020
> $ sudo lttng enable-event writeback_nothread -k
> Kernel event writeback_nothread created in channel channel0
> $ sudo lttng enable-channel ch1 -k
> Kernel channel ch1 enabled for session tst1
[...]
> $ sudo lttng disable-event writeback_nothread -k -c channel0
> Kernel event writeback_nothread disabled in channel channel0 for session tst1
> $ sudo lttng enable-event writeback_nothread -k -c ch1
> Error: Event writeback_nothread: Enable kernel event failed (channel ch1, session tst1)
> Warning: Some command(s) went wrong

   That is a known feature/limitation of LTTng: kernel events can only be assigned once (within a session).  User-space events can be assigned to multiple channels.

Daniel U. Thibault
Protection des systèmes et contremesures (PSC) | Systems Protection & Countermeasures (SPC)
Cyber sécurité pour les missions essentielles (CME) | Mission Critical Cyber Security (MCCS)
R & D pour la défense Canada - Valcartier (RDDC Valcartier) | Defence R&D Canada - Valcartier (DRDC Valcartier)
2459 route de la Bravoure
Québec QC  G3J 1X5
CANADA
Vox : (418) 844-4000 x4245
Fax : (418) 844-4538
NAC : 918V QSDJ <http://www.travelgis.com/map.asp?addr=918V%20QSDJ>
Gouvernement du Canada | Government of Canada
<http://www.valcartier.drdc-rddc.gc.ca/>