[lttng-dev] Clang plugin providing automatic application instrumentation
wen qun wang
xiaoxiao046 at gmail.com
Tue Mar 18 08:37:49 EDT 2014
Thanks for your help.
It seems that set_tracepoint is called by the void
__tracepoint_register_##_provider##___##_name(\lttng-ust-2.4.0\include\lttng\tracepoint.h
line 182).
But there is no function which invoke the function
__tracepoint_register_##_provider##___##_name,so when is the function
__tracepoint_register_##_provider##___##_name is called?
2014-03-18 19:55 GMT+08:00 Zifei Tong <zifeitong at gmail.com>:
> Hi,
>
> Please check the set_tracepoint() function in liblttng-ust/tracepoint.c
>
> /*
> * Sets the probe callback corresponding to one tracepoint.
> */
> static void set_tracepoint(struct tracepoint_entry **entry, struct
> tracepoint *elem, int active);
>
> I think probes are connected to tracepoints when user enable
> corresponding events.
>
> Hope that helps.
>
> Zifei Tong
>
> On Tue, Mar 18, 2014 at 5:08 PM, wen qun wang <xiaoxiao046 at gmail.com>
> wrote:
> > Hi,everyone.At first ,thanks for jeremie's help. I have completed
> toolchain
> > to gain an understanding of how the different pieces fit together.Then,
> I'm
> > going to through the studying the
> demo(/lttng-ust-2.4.0/doc/examples/demo)
> > of lttng-ust to understand the working principle of lttng.But now,I am in
> > trouble.
> > In /lttng-ust-2.4.0/doc/examples/demo/demo.c
> >
> > ##################
> > tracepoint(ust_test_demo2,done,42)
> > ###################
> >
> > I found the definition of tracepoint in
> > /lttng-ust-2.4.0/include/lttng/tracepoint.h
> >
> > ############################################################
> > #define tracepoint(provider, name, ...) \
> > do { \
> > STAP_PROBEV(provider, name, ## __VA_ARGS__); \
> > if (caa_unlikely(__tracepoint_##provider##___##name.state)) \
> > __tracepoint_cb_##provider##___##name(__VA_ARGS__); \
> > } while (0)
> > #################################################################
> >
> > then i found the definition of
> > "__tracepoint_cb_##provider##___##name(__VA_ARGS__)" in
> > /lttng-ust-2.4.0/include/lttng/tracepoint.h line 158
> >
> > ########################################################################
> > void
> __tracepoint_cb_##_provider##___##_name(_TP_ARGS_PROTO(__VA_ARGS__)) \
> > { \
> > struct tracepoint_probe *__tp_probe; \
> > \
> > if (caa_unlikely(!TP_RCU_LINK_TEST())) \
> > return; \
> > tp_rcu_read_lock_bp(); \
> > __tp_probe =
> > tp_rcu_dereference_bp(__tracepoint_##_provider##___##_name.probes); \
> > if (caa_unlikely(!__tp_probe)) \
> > goto end; \
> > do { \
> > void (*__tp_cb)(void) = __tp_probe->func; \
> > void *__tp_data = __tp_probe->data; \
> > \
> > URCU_FORCE_CAST(void (*)(_TP_ARGS_DATA_PROTO(__VA_ARGS__)), __tp_cb) \
> > (_TP_ARGS_DATA_VAR(__VA_ARGS__)); \
> > } while ((++__tp_probe)->func); \
> > end: \
> > tp_rcu_read_unlock_bp(); \
> > }
> > ####################################################################
> >
> > It seems that "__tracepoint_##_provider##___##_name" in
> > "__tracepoint_##_provider##___##_name.probes" is a struct of tracepoint.
> > we can found the macro TRACEPOINT_EVENT was used in
> > "lttng-ust-2.4.0\doc\examples\demo\ust_tests_demo.h".And the struct of
> > tracepoint was defined by the macro TRACEPOINT_EVENT.But the
> > __tracepoint_##_provider##___##_name.probes was set to null.
> >
> > #################################################
> > \lttng-ust-2.4.0\include\lttng\tracepoint.h line 342
> > #define _DEFINE_TRACEPOINT(_provider, _name, _args) \
> > extern int __tracepoint_provider_##_provider; \
> > static const char __tp_strtab_##_provider##___##_name[] \
> > __attribute__((section("__tracepoints_strings"))) = \
> > #_provider ":" #_name; \
> > struct tracepoint __tracepoint_##_provider##___##_name \
> > __attribute__((section("__tracepoints"))) = \
> > { \
> > __tp_strtab_##_provider##___##_name, \
> > 0, \
> > NULL, \---------------------------------------------->here is the probes.
> > _TRACEPOINT_UNDEFINED_REF(_provider), \
> > _TP_EXTRACT_STRING(_args), \
> > { }, \
> > }; \
> > static struct tracepoint * __tracepoint_ptr_##_provider##___##_name \
> > __attribute__((used, section("__tracepoints_ptrs"))) = \
> > &__tracepoint_##_provider##___##_name;
> > ###################################################################
> >
> > so i want to know that how the probes of the tracepoint struct should be
> > initialized,I can't find the source code.
> > My english is poor,i hope you can understand what i mean. Thank you very
> > much.
> >
> >
> >
> >
> >
> >
> > 2014-03-15 9:24 GMT+08:00 为王 <xiaoxiao046 at gmail.com>:
> >>
> >> thank you very much
> >>
> >>
> >> 2014-03-15 1:35 GMT+08:00 Jérémie Galarneau
> >> <jeremie.galarneau at efficios.com>:
> >>
> >>> On Wed, Mar 12, 2014 at 6:05 AM, 为王 <xiaoxiao046 at gmail.com> wrote:
> >>> > Hi All,I am a graduate student from Beijing University of Posts and
> >>> > Telecommunications. Due to my
> >>> > experience in windows kernel development and debugging technique,I am
> >>> > very
> >>> > interested in the lttng project.I want to make a contribution for the
> >>> > Clang
> >>> > plugin providing automatic application instrumentation after reading
> >>> > the
> >>> > project ideas for gsoc2014.I am also interested in reverse
> engineering
> >>> > and
> >>> > binary hack.
> >>> > The codes of lttng project have been downloaded for reading.Due to
> its
> >>> > large
> >>> > amount,i couldn't figure out a good way to understand it.So,i want to
> >>> > konw
> >>> > how should i proceed further.
> >>>
> >>> You should start by trying the complete toolchain to gain an
> >>> understanding of how the different pieces fit together. I wouldn't
> >>> suggest simply jumping into the code.
> >>>
> >>> Have a look at the guidelines posted on our GSoC 2014 wiki for more
> >>> information on how to submit a proposal [1].
> >>>
> >>> Let us know if you have more specific questions.
> >>>
> >>> Jérémie
> >>>
> >>> [1]
> >>>
> https://bugs.lttng.org/projects/lttng/wiki/Google_Summer_of_Code_2014#Guidelines-for-students-applying-to-GSoC
> >>>
> >>> > My english is poor,i hope you can understand what i mean. Thank you
> >>> > very
> >>> > much.
> >>> >
> >>> > _______________________________________________
> >>> > lttng-dev mailing list
> >>> > lttng-dev at lists.lttng.org
> >>> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> >>> >
> >>>
> >>>
> >>>
> >>> --
> >>> Jérémie Galarneau
> >>> EfficiOS Inc.
> >>> http://www.efficios.com
> >>
> >>
> >
> >
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev at lists.lttng.org
> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> >
>
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