Date: Mon, 13 Aug 2018 10:16:30 +0200 From: Willem Jan Withagen <wjw@digiware.nl> To: Yuri Pankov <yuripv@yuripv.net>, Konstantin Belousov <kostikbel@gmail.com> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Write a version for pthread_get_name_np Message-ID: <bc7cf9c0-1739-8b6d-7fc1-cfa469659d2a@digiware.nl> In-Reply-To: <34158602-9806-0553-af1c-e8dacbb0ffa0@yuripv.net> References: <7fa2b876-9397-da2b-cb29-56badf11b66d@ecoracks.nl> <42689feb-9bd4-429b-63d7-b9193123ee47@digiware.nl> <20180812205835.GB2340@kib.kiev.ua> <bdf7e3bd-e33f-019e-c6ff-a10e927e3a01@digiware.nl> <20180812225726.GC2340@kib.kiev.ua> <c99da03d-596f-9773-ab5b-df5c9d30fa27@digiware.nl> <20180812234800.GD2340@kib.kiev.ua> <34158602-9806-0553-af1c-e8dacbb0ffa0@yuripv.net>
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On 13/08/2018 02:24, Yuri Pankov wrote:
> Konstantin Belousov wrote:
>> On Mon, Aug 13, 2018 at 01:36:28AM +0200, Willem Jan Withagen wrote:
>>> On 13/08/2018 00:57, Konstantin Belousov wrote:
>>>> On Mon, Aug 13, 2018 at 12:01:03AM +0200, Willem Jan Withagen wrote:
>>>>> On 12/08/2018 22:58, Konstantin Belousov wrote:
>>>>>> On Sun, Aug 12, 2018 at 10:33:06PM +0200, Willem Jan Withagen wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> For some porting I'm trying to write a pthread_get_name_np(), but
>>>>>>> I have run into a snag....
>>>>>>> Tried some the the procstat code I would come up with:
>>>>>>>
>>>>>>> int pthread_get_name_np(pthread_t *thread,
>>>>>>> ššš ššššššššššššššššššššššš char *name, size_t len){
>>>>>>> ššš ššš struct procstat *procstat;
>>>>>>> ššš ššš int pid = getpid();
>>>>>>> ššš ššš unsigned int count, i;
>>>>>>> ššš ššš struct kinfo_proc *kip, *kipp;
>>>>>>>
>>>>>>> ššš ššš procstat = procstat_open_sysctl();
>>>>>>> ššš ššš kip = procstat_getprocs(procstat, KERN_PROC_PID |
>>>>>>> KERN_PROC_INC_THREAD,
>>>>>>> ššš ššššššššššš pid, &count);
>>>>>>> ššš ššš for (i = 0; i < count; i++) {
>>>>>>> ššš ššš ššš kipp = &kip[i];
>>>>>>> ššš ššš ššš printf("thread: %ld(0x%lx), %ld(0x%lx)\n", thread,
>>>>>>> thread,
>>>>>>> kipp->ki_tid, kipp->ki_tid);
>>>>>>> ššš ššš ššš if (thread == kipp->ki_tid) {
>>>>>>> ššš ššš ššš ššš kinfo_proc_thread_name(kipp, name, len);
>>>>>>> ššš ššš ššš }
>>>>>>> ššš ššš }
>>>>>>> ššš ššš return 0;
>>>>>>> }
>>>>>>>
>>>>>>> Problem only is that the TID value in what procstat_getprocs
>>>>>>> returns in
>>>>>>> ki_tid is nowhere near
>>>>>>> what pthread_self() returns.
>>>>>>> But both manual page and the include file describe the value as
>>>>>>> Thread ID.
>>>>>>> Only in sys/user.h the type is
>>>>>>> ššš ššš lwpid_t ki_tid;šššššššššššššššš /* XXXKSE thread id */
>>>>>>>
>>>>>>> What do I need to translate one tid into the other so I can really
>>>>>>> compare them?
>>>>>>
>>>>>> You need to cast pthread_t * to struct thread *, this is an internal
>>>>>> libthr structure which represents the thread in userspace.š The
>>>>>> structure field tid gives you the tid you want to pass to sysctl.
>>>>>
>>>>> mmmm,
>>>>>
>>>>> I'm afraid I'm not quit able to followup on your answer.
>>>>>
>>>>> Trying to find what to include to be able to cast this, I can only
>>>>> find
>>>>> a small bit defined in /usr/src/lib/libthr/thread/thr_private.h.
>>>>> /*
>>>>> ššš * lwpid_t is 32bit but kernel thr API exports tid as long type
>>>>> ššš * to preserve the ABI for M:N model in very early date (r131431).
>>>>> ššš */
>>>>> #define TID(thread)šššš ((uint32_t) ((thread)->tid))
>>>>>
>>>>> But that I cannot just "include" that file without a lot of mess, and
>>>>> then still it does not compile.
>>>>>
>>>>> So could you point me to where this private part of struct thread is
>>>>> hidding?
>>>> I do not understand your confusion. The thr_private.h header is only
>>>> for use by libthr, the FreeBSD threading library implementation. The
>>>> function that you are trying to implement, requires understanding of
>>>> the
>>>> libthr internals and can only be implemented as part of libthr.
>>>>
>>>> Any other attempt to translate libthr handle for thread into tid needs
>>>> same access to the struct pthread.
>>>
>>> Oke,
>>>
>>> I don't have more knowledge of (p)threads than just how to use it.
>>> I was trying to do this as a piece of code in the compat.cc of my
>>> ceph port.
>>>
>>> But trying to reread what you write is boils down to: there is no way to
>>> link a value returned by (struct pthread *)pthread_self() to the kd_tid
>>> value that can be found in the (struct kinfo_proc *) describing that
>>> same thread.
>> No, this is not what I said.
>>
>> I am claiming that this functionality must be implemented in libthr.
>> So if you want this function, it needs to be added to libthr, and it is
>> quite trivial to do.
>>
>> You can code it, or you might provide (draft of the) man page, and I
>> will code it according to the spec.
>
> How about the attached patch for man page part?
Thanx,
I guess that'll work.
Although I was following the procstat way and when there was no name set
we get a '-'. But if Konstatin is going to write it, it is his prerogative.
And I would expect it to be equivalent partner of thr_{set,get}_name as
well. But that could be added later in the man page.
--WjW
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