[lttng-dev] [RFC PATCH 0/2] Identify UST threads by changing thread names

[Mathieu Desnoyers]

----- On Jun 3, 2016, at 4:12 PM, Raphaël Beamonte raphael.beamonte at gmail.com wrote:

> Hi!
> 
> Thanks for all of your comments, I appreciate it!
> Thanks Jeremie for adding Mathieu in Cc, forgot to do it... Will
> remember next time! :)
> 
> 2016-06-02 9:22 GMT-04:00 Sebastien Boisvert <sboisvert at gydle.com>:
>> Do you know if the name of these listener threads can be set in their
>> constructor, directly
>> when they are brought into this world ?
> 
> pthread_create does not allow to specify a name when creating the new
> thread, as far as I know! That's why the 'lttng_ust_setustprocname()'
> function is called first thing in the ust_listener_thread function.
> 
>> Perhaps the availability of pthread_setname_np and/or pthread_set_name_np (you
>> have both names
>> in your patch 2) should be ascertained in another venue, such as the
>> configure.ac -- where it belongs.
> 
> True!
> 
> 2016-06-03 2:24 GMT-04:00 Mathieu Desnoyers <mathieu.desnoyers at efficios.com>:
>> ----- On Jun 3, 2016, at 8:18 AM, Mathieu Desnoyers
>> mathieu.desnoyers at efficios.com wrote:
>>> lttng-ust already uses libc for mutexes and other. So I don't see why
>>> you have to _add_ any explicit dependency there.
>>
>> and we already explicitly use pthread (pthread_create).
> 
> You're right, pthread is already used. However, when compiling the
> code without adding the pthread dependency, I get the following
> warning:
> 
> In file included from lttng-tracer.h:30:0,
>                 from lttng-ust-abi.c:50:
> compat.h: In function ‘lttng_ust_setustprocname’:
> compat.h:52:2: warning: implicit declaration of function
> ‘pthread_setname_np’ [-Wimplicit-function-declaration]
>  pthread_setname_np(pthread_self(), name);
>  ^
>  CC       lttng-context-procname.lo
> In file included from lttng-context-procname.c:28:0:
> compat.h: In function ‘lttng_ust_setustprocname’:
> compat.h:52:2: warning: implicit declaration of function
> ‘pthread_setname_np’ [-Wimplicit-function-declaration]
>  pthread_setname_np(pthread_self(), name);
>  ^
> 
> It seems to be because pthread is not specified as dependency for
> liblttng-ust-tracepoint in liblttng-ust/Makefile.am. However, perhaps
> that pthread dependency should be added elsewhere?

Seems fair.

Thanks,

Mathieu

> 
>>> About the glibc version, we should use autotools to detect the
>>> features supported by the system libc, and pass a config define
>>> to the source code, so we can use the glibc pthread_setname_np
>>> if available, else we keep the current behavior.
> 
> That's a good idea, will do!
> 
> I'll update and rebase the patch following your comments.
> If you have any other insight about the pthread dependency, I'm all ears!
> 
> Thanks,
> Raphaël

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com