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Hi,

There are two reasons:

* PyThread_get_thread_native_id() was only added recently (Python 3.8)
* PyThread_get_thread_native_id() is not portable and not available on
all platforms: the function is only declared if the
PY_HAVE_THREAD_NATIVE_ID macro is defined.

Maybe PyThreadState.thread_id could use
PyThread_get_thread_native_id() if avaialble, or
PyThread_get_thread_ident() otherwise. But that sounds like an
incompatible change.

Another approach would be to add a *new* structure member, like
thread_native_id. It would not exist if the PY_HAVE_THREAD_NATIVE_ID
macro is not defined.


Include/pythread.h:

#if defined(__APPLE__) || defined(__linux__) || defined(__FreeBSD__)
|| defined(__OpenBSD__) || defined(__NetBSD__) || defined(_WIN32) ||
defined(_AIX)
#define PY_HAVE_THREAD_NATIVE_ID
PyAPI_FUNC(unsigned long) PyThread_get_thread_native_id(void);
#endif


thread_pthread.h implementation:

unsigned long
PyThread_get_thread_native_id(void)
{
if (!initialized)
PyThread_init_thread();
#ifdef __APPLE__
uint64_t native_id;
(void) pthread_threadid_np(NULL, &native_id);
#elif defined(__linux__)
pid_t native_id;
native_id = syscall(SYS_gettid);
#elif defined(__FreeBSD__)
int native_id;
native_id = pthread_getthreadid_np();
#elif defined(__OpenBSD__)
pid_t native_id;
native_id = getthrid();
#elif defined(_AIX)
tid_t native_id;
native_id = thread_self();
#elif defined(__NetBSD__)
lwpid_t native_id;
native_id = _lwp_self();
#endif
return (unsigned long) native_id;
}

Victor
--
Night gathers, and now my watch begins. It shall not end until my death.


On Fri, Apr 16, 2021 at 10:47 PM Gabriele <phoenix1987@gmail.com> wrote:
>
> Hi all.
>
> My apologies if this is a topic that's been discussed already, but I
> wasn't able to locate anything in the archive on the subject. I was
> wondering if there's a fundamental reason for using
> PyThread_get_thread_ident instead of PyThread_get_thread_native_id for
> the value of the thread_id field of the PyThreadState object.
>
> The reason why I'm asking is that I would like to have easy access to
> the native TID on Linux to identify the /proc/stat file associated
> with the thread from an external process. At the moment I have to
> resort to calling process_vm_readv to copy the struct pthread over to
> local VM and then guess where the tid field might be. So, if there's
> no fundamental reason for thread_id to be PyThread_get_thread_ident, I
> would like to propose to change it to PyThread_get_thread_native_id
> instead.
>
> Thanks,
> Gabriele
>
> --
> "Egli è scritto in lingua matematica, e i caratteri son triangoli,
> cerchi, ed altre figure
> geometriche, senza i quali mezzi è impossibile a intenderne umanamente parola;
> senza questi è un aggirarsi vanamente per un oscuro laberinto."
>
> -- G. Galilei, Il saggiatore.
> _______________________________________________
> Python-Dev mailing list -- python-dev@python.org
> To unsubscribe send an email to python-dev-leave@python.org
> https://mail.python.org/mailman3/lists/python-dev.python.org/
> Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/3DOB6VUTAIJKK4SUGBYWL4QPWI2E5Q2T/
> Code of Conduct: http://python.org/psf/codeofconduct/
_______________________________________________
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Code of Conduct: http://python.org/psf/codeofconduct/

Hi Victor

Thanks for your reply. Indeed, upon further investigation, I have realised
changing the value of thread_id is not wise as there are other methods that
expect this field to be a pthread_t. I have opened issue
https://bugs.python.org/issue43879https://bugs.python.org/issue43879 to
have the new field added. I'm happy to do the work myself if it gets
accepted.

Cheers,
Gabriele

On Sat, 17 Apr 2021, 11:07 Victor Stinner, <vstinner@python.org> wrote:

> Hi,
>
> There are two reasons:
>
> * PyThread_get_thread_native_id() was only added recently (Python 3.8)
> * PyThread_get_thread_native_id() is not portable and not available on
> all platforms: the function is only declared if the
> PY_HAVE_THREAD_NATIVE_ID macro is defined.
>
> Maybe PyThreadState.thread_id could use
> PyThread_get_thread_native_id() if avaialble, or
> PyThread_get_thread_ident() otherwise. But that sounds like an
> incompatible change.
>
> Another approach would be to add a *new* structure member, like
> thread_native_id. It would not exist if the PY_HAVE_THREAD_NATIVE_ID
> macro is not defined.
>
>
> Include/pythread.h:
>
> #if defined(__APPLE__) || defined(__linux__) || defined(__FreeBSD__)
> || defined(__OpenBSD__) || defined(__NetBSD__) || defined(_WIN32) ||
> defined(_AIX)
> #define PY_HAVE_THREAD_NATIVE_ID
> PyAPI_FUNC(unsigned long) PyThread_get_thread_native_id(void);
> #endif
>
>
> thread_pthread.h implementation:
>
> unsigned long
> PyThread_get_thread_native_id(void)
> {
> if (!initialized)
> PyThread_init_thread();
> #ifdef __APPLE__
> uint64_t native_id;
> (void) pthread_threadid_np(NULL, &native_id);
> #elif defined(__linux__)
> pid_t native_id;
> native_id = syscall(SYS_gettid);
> #elif defined(__FreeBSD__)
> int native_id;
> native_id = pthread_getthreadid_np();
> #elif defined(__OpenBSD__)
> pid_t native_id;
> native_id = getthrid();
> #elif defined(_AIX)
> tid_t native_id;
> native_id = thread_self();
> #elif defined(__NetBSD__)
> lwpid_t native_id;
> native_id = _lwp_self();
> #endif
> return (unsigned long) native_id;
> }
>
> Victor
> --
> Night gathers, and now my watch begins. It shall not end until my death.
>
>
> On Fri, Apr 16, 2021 at 10:47 PM Gabriele <phoenix1987@gmail.com> wrote:
> >
> > Hi all.
> >
> > My apologies if this is a topic that's been discussed already, but I
> > wasn't able to locate anything in the archive on the subject. I was
> > wondering if there's a fundamental reason for using
> > PyThread_get_thread_ident instead of PyThread_get_thread_native_id for
> > the value of the thread_id field of the PyThreadState object.
> >
> > The reason why I'm asking is that I would like to have easy access to
> > the native TID on Linux to identify the /proc/stat file associated
> > with the thread from an external process. At the moment I have to
> > resort to calling process_vm_readv to copy the struct pthread over to
> > local VM and then guess where the tid field might be. So, if there's
> > no fundamental reason for thread_id to be PyThread_get_thread_ident, I
> > would like to propose to change it to PyThread_get_thread_native_id
> > instead.
> >
> > Thanks,
> > Gabriele
> >
> > --
> > "Egli è scritto in lingua matematica, e i caratteri son triangoli,
> > cerchi, ed altre figure
> > geometriche, senza i quali mezzi è impossibile a intenderne umanamente
> parola;
> > senza questi è un aggirarsi vanamente per un oscuro laberinto."
> >
> > -- G. Galilei, Il saggiatore.
> > _______________________________________________
> > Python-Dev mailing list -- python-dev@python.org
> > To unsubscribe send an email to python-dev-leave@python.org
> > https://mail.python.org/mailman3/lists/python-dev.python.org/
> > Message archived at
> https://mail.python.org/archives/list/python-dev@python.org/message/3DOB6VUTAIJKK4SUGBYWL4QPWI2E5Q2T/
> > Code of Conduct: http://python.org/psf/codeofconduct/
>