[lttng-dev] [BUG] lttng-sessiond

Hannes Weisbach hannes.weisbach at mailbox.tu-dresden.de
Fri Apr 24 05:52:07 EDT 2015


>> Can you share with us the code of your "hello" probe ?
I used the example code from
http://lttng.org/docs/#doc-instrumenting-linux-kernel-itself .

>> Which version or git commit of lttng-modules are you
>> using ?
I used the current master of the github mirrors, specifically:
lttng-tools: 94ffb05d6777efc0c40394d3df44a04feed92953
lttng-modules: d0558de29ca516e83b388b8028651f8b69288e4e
lttng-ust: 4bc1ccd721114691c6f0dbd65335b3c43c9f895f

> I think the two issues should be fixed by this new
> git commit in lttng-modules master branch:
> commit 66fd8d5e4a6080f1b2db0f525c26c07e5b723aab
> Author: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> Date:   Thu Apr 23 16:11:15 2015 -0400
>    Fix: double-unlock of session mutex
>    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> Can you give it a try ?
Yes, the mutex error goes away.  However, loading multiple probes with
either --kmod-probes or --extra-kmod-probes still does not work:
$ sudo lttng-sessiond -vvv --extra-kmod-probes=sched,napi
DEBUG1 - 11:42:18.492870 [5358/5358]: Modprobe successfully lttng-probe-napi (in modprobe_lttng() at modprobe.c:285)
sh: 1: Syntax error: "(" unexpected
DEBUG1 - 11:42:18.495037 [5358/5358]: Unable to load optional module (null); continuing (in modprobe_lttng() at modprobe.c:281)

Also, lttng-probe-regmap does not compile, but that might have to do
with my kernel version of 4.0.0-rc4 (commit
b314acaccd7e0d55314d96be4a33b5f50d0b3344 from

lttng-modules$ make KERNELDIR=/usr/src/linux-4.0.0-rc4-atlas+
make -C /usr/src/linux-4.0.0-rc4-atlas+ M=/home/hannesweisbach/atlas/lttng-modules modules
make[1]: Entering directory '/usr/src/linux-4.0.0-rc4-atlas+'
  CC [M]  /home/hannesweisbach/atlas/lttng-modules/probes/lttng-probe-regmap.o
In file included from /home/hannesweisbach/atlas/lttng-modules/probes/../instrumentation/events/lttng-module/../../../probes/define_trace.h:100:0,
                 from /home/hannesweisbach/atlas/lttng-modules/probes/../instrumentation/events/lttng-module/regmap.h:278,
                 from /home/hannesweisbach/atlas/lttng-modules/probes/lttng-probe-regmap.c:41:
/home/hannesweisbach/atlas/lttng-modules/probes/../instrumentation/events/lttng-module/../../../probes/lttng-events.h:134:6: error: conflicting types for ‘trace_regmap_reg_write’
 void trace_##_name(_proto);
/home/hannesweisbach/atlas/lttng-modules/probes/../instrumentation/events/lttng-module/../../../probes/lttng-events.h:99:2: note: in expansion of macro ‘LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP’
  LTTNG_TRACEPOINT_EVENT_INSTANCE_MAP(template, name, name, PARAMS(proto), PARAMS(args))
/home/hannesweisbach/atlas/lttng-modules/probes/../instrumentation/events/lttng-module/../../../probes/../instrumentation/events/lttng-module/regmap.h:34:1: note: in expansion of macro ‘LTTNG_TRACEPOINT_EVENT_INSTANCE’
 LTTNG_TRACEPOINT_EVENT_INSTANCE(regmap_reg, regmap_reg_write,
In file included from include/trace/events/regmap.h:8:0,
                 from /home/hannesweisbach/atlas/lttng-modules/probes/lttng-probe-regmap.c:32:
include/linux/tracepoint.h:169:21: note: previous definition of ‘trace_regmap_reg_write’ was here
  static inline void trace_##name(proto)    \
include/linux/tracepoint.h:325:3: note: in expansion of macro ‘__DECLARE_TRACE’
   __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1, \
include/linux/tracepoint.h:448:2: note: in expansion of macro ‘DECLARE_TRACE’
  DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
include/trace/events/regmap.h:40:1: note: in expansion of macro ‘DEFINE_EVENT’
 DEFINE_EVENT(regmap_reg, regmap_reg_write,

[ and so on, and so on … ]

Since I don't need the regmap probe I simply disabled it in
probes/Makefile.  Unfortunately, I don't have time to debug it myself.
If you want me to try another version, let me know.

Best regards,

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