From owner-freebsd-hackers@freebsd.org Sun Aug 12 23:36:31 2018 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 0A7141059C15 for ; Sun, 12 Aug 2018 23:36:31 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from smtp.digiware.nl (smtp.digiware.nl [176.74.240.9]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 9699C7FCC3 for ; Sun, 12 Aug 2018 23:36:30 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from router.digiware.nl (localhost.digiware.nl [127.0.0.1]) by smtp.digiware.nl (Postfix) with ESMTP id C5CC26CD5; Mon, 13 Aug 2018 01:36:28 +0200 (CEST) X-Virus-Scanned: amavisd-new at digiware.com Received: from smtp.digiware.nl ([127.0.0.1]) by router.digiware.nl (router.digiware.nl [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id KnemwLSWTLRp; Mon, 13 Aug 2018 01:36:28 +0200 (CEST) Received: from [192.168.11.152] (unknown [192.168.11.152]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.digiware.nl (Postfix) with ESMTPSA id D4DD66CCE; Mon, 13 Aug 2018 01:36:27 +0200 (CEST) Subject: Re: Write a version for pthread_get_name_np To: Konstantin Belousov Cc: FreeBSD Hackers References: <7fa2b876-9397-da2b-cb29-56badf11b66d@ecoracks.nl> <42689feb-9bd4-429b-63d7-b9193123ee47@digiware.nl> <20180812205835.GB2340@kib.kiev.ua> <20180812225726.GC2340@kib.kiev.ua> From: Willem Jan Withagen Message-ID: Date: Mon, 13 Aug 2018 01:36:28 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180812225726.GC2340@kib.kiev.ua> Content-Type: text/plain; charset=koi8-r; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.27 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 12 Aug 2018 23:36:31 -0000 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, >>>> ššššššššššššššššššššššš char *name, size_t len){ >>>> ššš struct procstat *procstat; >>>> ššš int pid = getpid(); >>>> ššš unsigned int count, i; >>>> ššš struct kinfo_proc *kip, *kipp; >>>> >>>> ššš procstat = procstat_open_sysctl(); >>>> ššš kip = procstat_getprocs(procstat, KERN_PROC_PID | KERN_PROC_INC_THREAD, >>>> ššššššššššš pid, &count); >>>> ššš for (i = 0; i < count; i++) { >>>> ššš ššš kipp = &kip[i]; >>>> ššš ššš printf("thread: %ld(0x%lx), %ld(0x%lx)\n", thread, thread, >>>> kipp->ki_tid, kipp->ki_tid); >>>> ššš ššš if (thread == kipp->ki_tid) { >>>> ššš ššš ššš kinfo_proc_thread_name(kipp, name, len); >>>> 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 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. 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. >> /* >> * lwpid_t is 32bit but kernel thr API exports tid as long type >> * to preserve the ABI for M:N model in very early date (r131431). >> */ >> #define TID(thread) ((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. And even though (struct thread *) has a field: lwpid_t td_tid; /* (b) Thread ID. */ that field seems to be stuck at value td_tid = 32767 every time I look at it with gdb. So it is a pity that this is not going to work this way. --WjW