[lttng-dev] traces omissions

[Mathieu Desnoyers]

* Sébastien Barthélémy (barthelemy at crans.org) wrote:
> Hello all,
> 
> I have yet another difficulty using LTTng.
> 
> I run a program which dlopens a module (called DCM) which is
> instrumented with ust (provider == qi_dcm), and which calls functions
> from a processsyncclient library (PSC for short), also instrumented
> with ust (provider == qi_bn_ipc_psc).
> 
> When I run the program, I ld_preload the two probes provider as in
> 
> LD_PRELOAD="$PREFIX/lib/libtp_processsyncclient_pipe.so
> $PREFIX/lib/libtp_dcm.so" LD_LIBRARY_PATH=$PREFIX/lib
> $PREFIX/bin/naoqi-bin &
> 
> This used to work, but when I run it now, I only get traces from the
> processsyncclient probes, not from the DCM ones. However, they are
> triggered by the same code paths, so I expect to get events from both
> of them.
> 
> I checked that the probes are correctly registered:
> 
> libust[3739/3739]: just registered probe qi_dcm containing 2 events
> (in ltt_probe_register() at ltt-probes.c:109)
> libust[3739/3739]: just registered probe qi_bn_ipc_psc containing 3
> events (in ltt_probe_register() at ltt-probes.c:109)
> 
> and that I have symbols from both of them in the DCM module (so it not
> a simple #define error):
> 
> $ nm libdcm_hal.so |grep _qi_
> 0005cab4 r _ZL26__tp_strtab_qi_dcm___state
> 0006c22c d _ZL31__tracepoint_ptr_qi_dcm___state
> 0005cad8 r _ZL35__tp_strtab_qi_bn_ipc_psc___waiting
> 0005cac1 r _ZL35__tp_strtab_qi_dcm___clock_realtime
> 0005cb0f r _ZL38__tp_strtab_qi_bn_ipc_psc___notify_end
> 0006c234 d _ZL40__tracepoint_ptr_qi_bn_ipc_psc___waiting
> 0006c230 d _ZL40__tracepoint_ptr_qi_dcm___clock_realtime
> 0006c23c d _ZL43__tracepoint_ptr_qi_bn_ipc_psc___notify_end
> 0005caf0 r _ZL44__tp_strtab_qi_bn_ipc_psc___finished_waiting
> 0006c238 d _ZL49__tracepoint_ptr_qi_bn_ipc_psc___finished_waiting
> 00040566 t __tracepoint_cb_qi_dcm___clock_realtime
> 000404c7 t __tracepoint_cb_qi_dcm___state
> 0006c214 D __tracepoint_qi_bn_ipc_psc___finished_waiting
> 0006c220 D __tracepoint_qi_bn_ipc_psc___notify_end
> 0006c208 D __tracepoint_qi_bn_ipc_psc___waiting
> 0006c1fc D __tracepoint_qi_dcm___clock_realtime
> 0006c1f0 D __tracepoint_qi_dcm___state
> 
> 
> I also get these messages (not sure what they mean):
> 
> liblttng_ust_tracepoint[3739/3739]: just registered a tracepoints
> section from 0xb1fa1860 and having 1 tracepoints (in
> tracepoint_register_lib() at tracepoint.c:610)
> liblttng_ust_tracepoint[3739/3739]: just registered a tracepoints
> section from 0xb203822c and having 5 tracepoints (in
> tracepoint_register_lib() at tracepoint.c:610)
> liblttng_ust_tracepoint[3739/3739]: just registered a tracepoints
> section from 0xb04b06f4 and having 2 tracepoints (in
> tracepoint_register_lib() at tracepoint.c:610)
> 
> Is this use case expected?
> 
> I fear I'm running out of ideas, how could investigate the matter further?

This rather sounds like an event name typo in create-event. Can you
provide the exact list of lttng commands you used ?

Thanks,

Mathieu

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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com