[lttng-dev] Odd behaviour of lttng 2.0 kernel event listing

[David Goulet]

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This is very odd...

The "DEBUG1: SIGCHLD catched [in sighandler() at lttng.c:179]" shows you that
when this signal is caught by the lttng client, it means that the session daemon
is ready hence the lttng modules are loaded for sure. The session daemon send
this signal only when it's ready to receive commands.

I think I have a 2.6.38 kernel hanging around somewhere. I'll try to reproduce
this problem.

In the meantime, change the lttng client to exec the session daemon in verbose mode:

diff --git a/src/bin/lttng/lttng.c b/src/bin/lttng/lttng.c
index 3181d90..2dacf8f 100644
- --- a/src/bin/lttng/lttng.c
+++ b/src/bin/lttng/lttng.c
@@ -286,7 +286,7 @@ static int spawn_sessiond(char *pathname)
                 * Spawn session daemon and tell
                 * it to signal us when ready.
                 */
- -               execlp(pathname, "lttng-sessiond", "--sig-parent", "--quiet",
NULL);
+               execlp(pathname, "lttng-sessiond", "--sig-parent", "-vvv", NULL);
                /* execlp only returns if error happened */
                if (errno == ENOENT) {
                        ERR("No session daemon found. Use --sessiond-path.");

And send us the session daemon debug output.

Thanks!
David

On 12-01-20 03:50 PM, Thibault, Daniel wrote:
>> Can you please try this commit :
>> commit 6725fe1993a3c70c5fddecf5a458f03b08852edd
>> Date:   Fri Jan 20 15:07:15 2012 -0500
>> Fix off-by-one and double list size instead of steady increment
> 
>    No problem.  In both senses of the expression: bootstrap, config, make, install went without a problem.
> 
>    No luck: '$ sudo lttng list -k' *still* anonymises after 'kvm_msi_set_irq (type: tracepoint)'.
> 
>    For chuckles, I ran 'sudo lttng -v list -k'.  This only adds two debug lines at the beginning:
> 
>> Spawning a session daemon
>> DEBUG1: SIGCHLD catched [in sighandler() at lttng.c:179]
>> DEBUG1: Getting kernel tracing events [in list_kernel_events() at commands/list.c:277]
>> [rest as before]
> 
>    By the way, that "catched" should be "caught".
> 
>    Any code you'd like me to inject in liblttng-ctl or wherever?
> 
> Daniel U. Thibault
> R & D pour la défense Canada - Valcartier (RDDC Valcartier) / Defence R&D Canada - Valcartier (DRDC Valcartier)
> Système de systèmes (SdS) / System of Systems (SoS)
> Solutions informatiques et expérimentations (SIE) / Computing Solutions and Experimentations (CSE)
> 2459 Boul. Pie XI Nord
> Québec, QC  G3J 1X5
> CANADA
> Vox : (418) 844-4000 x4245
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> NAC: 918V QSDJ
> Gouvernement du Canada / Government of Canada
> <http://www.valcartier.drdc-rddc.gc.ca/>
> 
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