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

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

[Raphaël Beamonte]

Hi,

This is an RFC patch for comments and ideas about how this should be
done. In recent work I've been doing, I found out that some UST-
instrumented userspace process was preempting itself. Looking further,
it was not the same TID, but the same process name. These processes
were LTTng-UST listener threads, but were not identified as so.
Adding a simple symbol, such as "-ust" or "-lttng" at the end of the
process name would help to identify such process directly in the
generated trace.

You'll find below two different implementations with their pros
and cons, for which the "-ust" symbol was choosen:


1/ An implementation using prctl
	It works properly on Linux, but I didn't find a way to make
	it work under FreeBSD, hence the empty function in FreeBSD
	case (keeping the situation as it is now).

Raphaël Beamonte (1):
  Add -ust to the name of UST threads of the application

 liblttng-ust/compat.h         | 22 ++++++++++++++++++++++
 liblttng-ust/lttng-ust-comm.c |  2 ++
 2 files changed, 24 insertions(+)



2/ An implementation using pthread
	It works on both Linux and FreeBSD, but requires to add a
	link to the pthread library in liblttng-ust Makefile.am.
	Also, this approach relies on the presence of the
	pthread_setname_np function, which was included in glibc
	2.12, meaning it will not work with older versions (but
	this should not be a problem?)

Raphaël Beamonte (1):
  Add -ust to the name of UST threads of the application

 liblttng-ust/Makefile.am      |  1 +
 liblttng-ust/compat.h         | 35 +++++++++++++++++++++++++++++++++++
 liblttng-ust/lttng-ust-comm.c |  2 ++
 3 files changed, 38 insertions(+)



I'll wait for your comments and ideas on that subject.

Thanks,
Raphaël


-- 
2.1.4

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Re: [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@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@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@efficios.com>:
>> ----- On Jun 3, 2016, at 8:18 AM, Mathieu Desnoyers
>> mathieu.desnoyers@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
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Re: [RFC PATCH 0/2] Identify UST threads by changing thread names

[Raphaël Beamonte]

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@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@efficios.com>:
> ----- On Jun 3, 2016, at 8:18 AM, Mathieu Desnoyers mathieu.desnoyers@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?

>> 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
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Re: [RFC PATCH 0/2] Identify UST threads by changing thread names

[Mathieu Desnoyers]

----- On Jun 3, 2016, at 8:18 AM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:

> ----- On Jun 3, 2016, at 8:11 AM, Jeremie Galarneau
> jeremie.galarneau@efficios.com wrote:
> 
>> And, of course, I forget to add Mathieu in CC... Coffee time!
>> 
>> Jérémie
>> 
>> On Fri, Jun 3, 2016 at 2:10 AM, Jérémie Galarneau
>> <jeremie.galarneau@efficios.com> wrote:
>>> Hi Raphaël,
>>>
>>> Adding Mathieu in CC. Please make sure you CC the maintainers when
>>> submitting a patch.
>>>
>>> Regards,
>>> Jérémie
>>>
>>> On Wed, Jun 1, 2016 at 11:04 AM, Raphaël Beamonte
>>> <raphael.beamonte@gmail.com> wrote:
>>>> Hi,
>>>>
>>>> I did not get any feedback about this, any thoughts ?
>>>>
>>>> Thanks,
>>>> Raphaël
>>>>
>>>> 2016-04-21 16:50 GMT-04:00 Raphaël Beamonte <raphael.beamonte@gmail.com>:
>>>>> Hi,
>>>>>
>>>>> This is an RFC patch for comments and ideas about how this should be
>>>>> done. In recent work I've been doing, I found out that some UST-
>>>>> instrumented userspace process was preempting itself. Looking further,
>>>>> it was not the same TID, but the same process name. These processes
>>>>> were LTTng-UST listener threads, but were not identified as so.
>>>>> Adding a simple symbol, such as "-ust" or "-lttng" at the end of the
>>>>> process name would help to identify such process directly in the
>>>>> generated trace.
>>>>>
>>>>> You'll find below two different implementations with their pros
>>>>> and cons, for which the "-ust" symbol was choosen:
>>>>>
>>>>>
>>>>> 1/ An implementation using prctl
>>>>>         It works properly on Linux, but I didn't find a way to make
>>>>>         it work under FreeBSD, hence the empty function in FreeBSD
>>>>>         case (keeping the situation as it is now).
>>>>>
>>>>> Raphaël Beamonte (1):
>>>>>   Add -ust to the name of UST threads of the application
>>>>>
>>>>>  liblttng-ust/compat.h         | 22 ++++++++++++++++++++++
>>>>>  liblttng-ust/lttng-ust-comm.c |  2 ++
>>>>>  2 files changed, 24 insertions(+)
>>>>>
>>>>>
>>>>>
>>>>> 2/ An implementation using pthread
>>>>>         It works on both Linux and FreeBSD, but requires to add a
>>>>>         link to the pthread library in liblttng-ust Makefile.am.
>>>>>         Also, this approach relies on the presence of the
>>>>>         pthread_setname_np function, which was included in glibc
>>>>>         2.12, meaning it will not work with older versions (but
>>>>>         this should not be a problem?)
> 
> 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).

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.
> 
> Thoughts ?
> 
> Thanks,
> 
> Mathieu
> 
>>>>>
>>>>> Raphaël Beamonte (1):
>>>>>   Add -ust to the name of UST threads of the application
>>>>>
>>>>>  liblttng-ust/Makefile.am      |  1 +
>>>>>  liblttng-ust/compat.h         | 35 +++++++++++++++++++++++++++++++++++
>>>>>  liblttng-ust/lttng-ust-comm.c |  2 ++
>>>>>  3 files changed, 38 insertions(+)
>>>>>
>>>>>
>>>>>
>>>>> I'll wait for your comments and ideas on that subject.
>>>>>
>>>>> Thanks,
>>>>> Raphaël
>>>>>
>>>>>
>>>>> --
>>>>> 2.1.4
>>>>>
>>>> _______________________________________________
>>>> lttng-dev mailing list
>>>> lttng-dev@lists.lttng.org
>>>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>>
>>>
>>>
>>> --
>>> Jérémie Galarneau
>>> EfficiOS Inc.
>>> http://www.efficios.com
>> 
>> 
>> 
>> --
>> Jérémie Galarneau
>> EfficiOS Inc.
>> http://www.efficios.com
> 
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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Re: [RFC PATCH 0/2] Identify UST threads by changing thread names

[Mathieu Desnoyers]

----- On Jun 3, 2016, at 8:11 AM, Jeremie Galarneau jeremie.galarneau@efficios.com wrote:

> And, of course, I forget to add Mathieu in CC... Coffee time!
> 
> Jérémie
> 
> On Fri, Jun 3, 2016 at 2:10 AM, Jérémie Galarneau
> <jeremie.galarneau@efficios.com> wrote:
>> Hi Raphaël,
>>
>> Adding Mathieu in CC. Please make sure you CC the maintainers when
>> submitting a patch.
>>
>> Regards,
>> Jérémie
>>
>> On Wed, Jun 1, 2016 at 11:04 AM, Raphaël Beamonte
>> <raphael.beamonte@gmail.com> wrote:
>>> Hi,
>>>
>>> I did not get any feedback about this, any thoughts ?
>>>
>>> Thanks,
>>> Raphaël
>>>
>>> 2016-04-21 16:50 GMT-04:00 Raphaël Beamonte <raphael.beamonte@gmail.com>:
>>>> Hi,
>>>>
>>>> This is an RFC patch for comments and ideas about how this should be
>>>> done. In recent work I've been doing, I found out that some UST-
>>>> instrumented userspace process was preempting itself. Looking further,
>>>> it was not the same TID, but the same process name. These processes
>>>> were LTTng-UST listener threads, but were not identified as so.
>>>> Adding a simple symbol, such as "-ust" or "-lttng" at the end of the
>>>> process name would help to identify such process directly in the
>>>> generated trace.
>>>>
>>>> You'll find below two different implementations with their pros
>>>> and cons, for which the "-ust" symbol was choosen:
>>>>
>>>>
>>>> 1/ An implementation using prctl
>>>>         It works properly on Linux, but I didn't find a way to make
>>>>         it work under FreeBSD, hence the empty function in FreeBSD
>>>>         case (keeping the situation as it is now).
>>>>
>>>> Raphaël Beamonte (1):
>>>>   Add -ust to the name of UST threads of the application
>>>>
>>>>  liblttng-ust/compat.h         | 22 ++++++++++++++++++++++
>>>>  liblttng-ust/lttng-ust-comm.c |  2 ++
>>>>  2 files changed, 24 insertions(+)
>>>>
>>>>
>>>>
>>>> 2/ An implementation using pthread
>>>>         It works on both Linux and FreeBSD, but requires to add a
>>>>         link to the pthread library in liblttng-ust Makefile.am.
>>>>         Also, this approach relies on the presence of the
>>>>         pthread_setname_np function, which was included in glibc
>>>>         2.12, meaning it will not work with older versions (but
>>>>         this should not be a problem?)

lttng-ust already uses libc for mutexes and other. So I don't see why
you have to _add_ any explicit dependency there.

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.

Thoughts ?

Thanks,

Mathieu

>>>>
>>>> Raphaël Beamonte (1):
>>>>   Add -ust to the name of UST threads of the application
>>>>
>>>>  liblttng-ust/Makefile.am      |  1 +
>>>>  liblttng-ust/compat.h         | 35 +++++++++++++++++++++++++++++++++++
>>>>  liblttng-ust/lttng-ust-comm.c |  2 ++
>>>>  3 files changed, 38 insertions(+)
>>>>
>>>>
>>>>
>>>> I'll wait for your comments and ideas on that subject.
>>>>
>>>> Thanks,
>>>> Raphaël
>>>>
>>>>
>>>> --
>>>> 2.1.4
>>>>
>>> _______________________________________________
>>> lttng-dev mailing list
>>> lttng-dev@lists.lttng.org
>>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>
>>
>>
>> --
>> Jérémie Galarneau
>> EfficiOS Inc.
>> http://www.efficios.com
> 
> 
> 
> --
> Jérémie Galarneau
> EfficiOS Inc.
> http://www.efficios.com

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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Re: [RFC PATCH 0/2] Identify UST threads by changing thread names

[Jérémie Galarneau]

And, of course, I forget to add Mathieu in CC... Coffee time!

Jérémie

On Fri, Jun 3, 2016 at 2:10 AM, Jérémie Galarneau
<jeremie.galarneau@efficios.com> wrote:
> Hi Raphaël,
>
> Adding Mathieu in CC. Please make sure you CC the maintainers when
> submitting a patch.
>
> Regards,
> Jérémie
>
> On Wed, Jun 1, 2016 at 11:04 AM, Raphaël Beamonte
> <raphael.beamonte@gmail.com> wrote:
>> Hi,
>>
>> I did not get any feedback about this, any thoughts ?
>>
>> Thanks,
>> Raphaël
>>
>> 2016-04-21 16:50 GMT-04:00 Raphaël Beamonte <raphael.beamonte@gmail.com>:
>>> Hi,
>>>
>>> This is an RFC patch for comments and ideas about how this should be
>>> done. In recent work I've been doing, I found out that some UST-
>>> instrumented userspace process was preempting itself. Looking further,
>>> it was not the same TID, but the same process name. These processes
>>> were LTTng-UST listener threads, but were not identified as so.
>>> Adding a simple symbol, such as "-ust" or "-lttng" at the end of the
>>> process name would help to identify such process directly in the
>>> generated trace.
>>>
>>> You'll find below two different implementations with their pros
>>> and cons, for which the "-ust" symbol was choosen:
>>>
>>>
>>> 1/ An implementation using prctl
>>>         It works properly on Linux, but I didn't find a way to make
>>>         it work under FreeBSD, hence the empty function in FreeBSD
>>>         case (keeping the situation as it is now).
>>>
>>> Raphaël Beamonte (1):
>>>   Add -ust to the name of UST threads of the application
>>>
>>>  liblttng-ust/compat.h         | 22 ++++++++++++++++++++++
>>>  liblttng-ust/lttng-ust-comm.c |  2 ++
>>>  2 files changed, 24 insertions(+)
>>>
>>>
>>>
>>> 2/ An implementation using pthread
>>>         It works on both Linux and FreeBSD, but requires to add a
>>>         link to the pthread library in liblttng-ust Makefile.am.
>>>         Also, this approach relies on the presence of the
>>>         pthread_setname_np function, which was included in glibc
>>>         2.12, meaning it will not work with older versions (but
>>>         this should not be a problem?)
>>>
>>> Raphaël Beamonte (1):
>>>   Add -ust to the name of UST threads of the application
>>>
>>>  liblttng-ust/Makefile.am      |  1 +
>>>  liblttng-ust/compat.h         | 35 +++++++++++++++++++++++++++++++++++
>>>  liblttng-ust/lttng-ust-comm.c |  2 ++
>>>  3 files changed, 38 insertions(+)
>>>
>>>
>>>
>>> I'll wait for your comments and ideas on that subject.
>>>
>>> Thanks,
>>> Raphaël
>>>
>>>
>>> --
>>> 2.1.4
>>>
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev@lists.lttng.org
>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
>
>
> --
> Jérémie Galarneau
> EfficiOS Inc.
> http://www.efficios.com



-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com
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Re: [RFC PATCH 0/2] Identify UST threads by changing thread names

[Jérémie Galarneau]

Hi Raphaël,

Adding Mathieu in CC. Please make sure you CC the maintainers when
submitting a patch.

Regards,
Jérémie

On Wed, Jun 1, 2016 at 11:04 AM, Raphaël Beamonte
<raphael.beamonte@gmail.com> wrote:
> Hi,
>
> I did not get any feedback about this, any thoughts ?
>
> Thanks,
> Raphaël
>
> 2016-04-21 16:50 GMT-04:00 Raphaël Beamonte <raphael.beamonte@gmail.com>:
>> Hi,
>>
>> This is an RFC patch for comments and ideas about how this should be
>> done. In recent work I've been doing, I found out that some UST-
>> instrumented userspace process was preempting itself. Looking further,
>> it was not the same TID, but the same process name. These processes
>> were LTTng-UST listener threads, but were not identified as so.
>> Adding a simple symbol, such as "-ust" or "-lttng" at the end of the
>> process name would help to identify such process directly in the
>> generated trace.
>>
>> You'll find below two different implementations with their pros
>> and cons, for which the "-ust" symbol was choosen:
>>
>>
>> 1/ An implementation using prctl
>>         It works properly on Linux, but I didn't find a way to make
>>         it work under FreeBSD, hence the empty function in FreeBSD
>>         case (keeping the situation as it is now).
>>
>> Raphaël Beamonte (1):
>>   Add -ust to the name of UST threads of the application
>>
>>  liblttng-ust/compat.h         | 22 ++++++++++++++++++++++
>>  liblttng-ust/lttng-ust-comm.c |  2 ++
>>  2 files changed, 24 insertions(+)
>>
>>
>>
>> 2/ An implementation using pthread
>>         It works on both Linux and FreeBSD, but requires to add a
>>         link to the pthread library in liblttng-ust Makefile.am.
>>         Also, this approach relies on the presence of the
>>         pthread_setname_np function, which was included in glibc
>>         2.12, meaning it will not work with older versions (but
>>         this should not be a problem?)
>>
>> Raphaël Beamonte (1):
>>   Add -ust to the name of UST threads of the application
>>
>>  liblttng-ust/Makefile.am      |  1 +
>>  liblttng-ust/compat.h         | 35 +++++++++++++++++++++++++++++++++++
>>  liblttng-ust/lttng-ust-comm.c |  2 ++
>>  3 files changed, 38 insertions(+)
>>
>>
>>
>> I'll wait for your comments and ideas on that subject.
>>
>> Thanks,
>> Raphaël
>>
>>
>> --
>> 2.1.4
>>
> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev



-- 
Jérémie Galarneau
EfficiOS Inc.
http://www.efficios.com
_______________________________________________
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Re: [RFC PATCH 0/2] Identify UST threads by changing thread names

[Sebastien Boisvert]

Hi Raphaël,

> Hi,
> 
> This is an RFC patch for comments and ideas about how this should be
> done. In recent work I've been doing, I found out that some UST-
> instrumented userspace process was preempting itself. Looking further,
> it was not the same TID, but the same process name. These processes
> were LTTng-UST listener threads, but were not identified as so.
> Adding a simple symbol, such as "-ust" or "-lttng" at the end of the
> process name would help to identify such process directly in the
> generated trace.

Do you know if the name of these listener threads can be set in their constructor, directly
when they are brought into this world ?

> 
> You'll find below two different implementations with their pros
> and cons, for which the "-ust" symbol was choosen:
> 
> 
> 1/ An implementation using prctl
> 	It works properly on Linux, but I didn't find a way to make
> 	it work under FreeBSD, hence the empty function in FreeBSD
> 	case (keeping the situation as it is now).
> 
> Raphaël Beamonte (1):
>   Add -ust to the name of UST threads of the application
> 
>  liblttng-ust/compat.h         | 22 ++++++++++++++++++++++
>  liblttng-ust/lttng-ust-comm.c |  2 ++
>  2 files changed, 24 insertions(+)
> 
> 

I prefer this one. It is less complex, in my opinion.

> 
> 2/ An implementation using pthread
> 	It works on both Linux and FreeBSD, but requires to add a
> 	link to the pthread library in liblttng-ust Makefile.am.
> 	Also, this approach relies on the presence of the
> 	pthread_setname_np function, which was included in glibc
> 	2.12, meaning it will not work with older versions (but
> 	this should not be a problem?)
> 
> Raphaël Beamonte (1):
>   Add -ust to the name of UST threads of the application
> 
>  liblttng-ust/Makefile.am      |  1 +
>  liblttng-ust/compat.h         | 35 +++++++++++++++++++++++++++++++++++
>  liblttng-ust/lttng-ust-comm.c |  2 ++
>  3 files changed, 38 insertions(+)
> 

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.

> 
> 
> I'll wait for your comments and ideas on that subject.
> 
> Thanks,
> Raphaël
> 
> 
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Re: [RFC PATCH 0/2] Identify UST threads by changing thread names

[Raphaël Beamonte]

Hi,

I did not get any feedback about this, any thoughts ?

Thanks,
Raphaël

2016-04-21 16:50 GMT-04:00 Raphaël Beamonte <raphael.beamonte@gmail.com>:
> Hi,
>
> This is an RFC patch for comments and ideas about how this should be
> done. In recent work I've been doing, I found out that some UST-
> instrumented userspace process was preempting itself. Looking further,
> it was not the same TID, but the same process name. These processes
> were LTTng-UST listener threads, but were not identified as so.
> Adding a simple symbol, such as "-ust" or "-lttng" at the end of the
> process name would help to identify such process directly in the
> generated trace.
>
> You'll find below two different implementations with their pros
> and cons, for which the "-ust" symbol was choosen:
>
>
> 1/ An implementation using prctl
>         It works properly on Linux, but I didn't find a way to make
>         it work under FreeBSD, hence the empty function in FreeBSD
>         case (keeping the situation as it is now).
>
> Raphaël Beamonte (1):
>   Add -ust to the name of UST threads of the application
>
>  liblttng-ust/compat.h         | 22 ++++++++++++++++++++++
>  liblttng-ust/lttng-ust-comm.c |  2 ++
>  2 files changed, 24 insertions(+)
>
>
>
> 2/ An implementation using pthread
>         It works on both Linux and FreeBSD, but requires to add a
>         link to the pthread library in liblttng-ust Makefile.am.
>         Also, this approach relies on the presence of the
>         pthread_setname_np function, which was included in glibc
>         2.12, meaning it will not work with older versions (but
>         this should not be a problem?)
>
> Raphaël Beamonte (1):
>   Add -ust to the name of UST threads of the application
>
>  liblttng-ust/Makefile.am      |  1 +
>  liblttng-ust/compat.h         | 35 +++++++++++++++++++++++++++++++++++
>  liblttng-ust/lttng-ust-comm.c |  2 ++
>  3 files changed, 38 insertions(+)
>
>
>
> I'll wait for your comments and ideas on that subject.
>
> Thanks,
> Raphaël
>
>
> --
> 2.1.4
>
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