From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <54D8E83F.6020601@control.lth.se> Date: Mon, 09 Feb 2015 18:02:55 +0100 From: Anders Blomdell MIME-Version: 1.0 References: <54D4D409.2020708@control.lth.se> <54D4D9B2.8090805@xenomai.org> <54D4DF0C.2080007@control.lth.se> <54D4E285.9000906@xenomai.org> <54D4E44B.4060403@control.lth.se> <20150206161215.GC27277@hermes.click-hack.org> <20150206161626.GD27277@hermes.click-hack.org> <54D8D7D5.2060000@control.lth.se> <20150209155716.GE3200@hermes.click-hack.org> <54D8DC0B.3070107@control.lth.se> <20150209162409.GF3200@hermes.click-hack.org> In-Reply-To: <20150209162409.GF3200@hermes.click-hack.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Subject: Re: [Xenomai] Mixing linux and alchemy (cobalt) calls List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: "Xenomai@xenomai.org" On 2015-02-09 17:24, Gilles Chanteperdrix wrote: > On Mon, Feb 09, 2015 at 05:10:51PM +0100, Anders Blomdell wrote: >> On 2015-02-09 16:57, Gilles Chanteperdrix wrote: >>> On Mon, Feb 09, 2015 at 04:52:53PM +0100, Anders Blomdell wrote: >>>> On 2015-02-06 17:16, Gilles Chanteperdrix wrote: >>>>> On Fri, Feb 06, 2015 at 05:12:15PM +0100, Gilles Chanteperdrix wrote: >>>>>> On Fri, Feb 06, 2015 at 04:56:59PM +0100, Anders Blomdell wrote: >>>>>>> On 2015-02-06 16:49, Philippe Gerum wrote: >>>>>>>> On 02/06/2015 04:34 PM, Anders Blomdell wrote: >>>>>>>>> On 2015-02-06 16:11, Philippe Gerum wrote: >>>>>>>>>> On 02/06/2015 03:47 PM, Anders Blomdell wrote: >>>>>>>>>>> I have an application that need both realtime and linux sockets, am I correct in assuming that >>>>>>>>>>> withe the alchemy skin I could access them like >>>>>>>>>>> >>>>>>>>>>> socket(... // Linux version >>>>>>>>>>> __real_socket(... // Linux version >>>>>>>>>>> __cobalt_socket(... // Alchemy/cobalt version >>>>>>>>>>> >>>>>>>>>>> while under the cobalt skin, it would be: >>>>>>>>>>> >>>>>>>>>>> socket(... // Alchemy/cobalt version >>>>>>>>>>> __real_socket(... // Linux version >>>>>>>>>>> __cobalt_socket(... // Alchemy/cobalt version >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> This depends on the LDFLAGS retrieved from xeno-config: >>>>>>>>>> >>>>>>>>>> 1. with --posix mentioned in the xeno-config --ldflags request >>>>>>>>>> >>>>>>>>>> socket(...), __cobalt_socket(...) or __RT(socket(...)) => Cobalt >>>>>>>>>> implementation >>>>>>>>>> __real_socket(...) or __STD(socket(...)) => glibc service >>>>>>>>>> >>>>>>>>>> 2. without --posix mentioned in the xeno-config --ldflags request >>>>>>>>>> >>>>>>>>>> __cobalt_socket(...) or __RT(socket(...)) => Cobalt implementation >>>>>>>>>> socket(...) or __STD(socket(...)) => glibc service >>>>>>>>>> >>>>>>>>>> e.g. >>>>>>>>>> >>>>>>>>>> - the application only wants to access the POSIX services implemented by >>>>>>>>>> Cobalt using the regular POSIX names: LDFLAGS should contain the output of: >>>>>>>>>> $ xeno-config --posix --ldflags, or --cobalt --ldflags. >>>>>>>>>> >>>>>>>>>> - the application wants to access the POSIX services implemented by >>>>>>>>>> Cobalt using the regular POSIX names, and the alchemy API: LDFLAGS >>>>>>>>>> should contain the output of: >>>>>>>>>> $ xeno-config --posix --alchemy --ldflags, or --cobalt --alchemy --ldflags. >>>>>>>>>> >>>>>>>>>> - the application wants to access the POSIX services implemented by >>>>>>>>>> Cobalt solely via the explicit POSIX wrappers, and the alchemy API: >>>>>>>>>> LDFLAGS should contain the output of (i.e. omitting --posix): >>>>>>>>>> $ xeno-config --alchemy --ldflags, or --alchemy --ldflags. >>>>>>>>>> >>>>>>>>>> NOTE: using __RT() is preferred to calling __cobalt(), in case an API >>>>>>>>>> stacked over the Cobalt POSIX API redefines its own implementation of >>>>>>>>>> POSIX services over the dual kernel. __RT() would call the stacked >>>>>>>>>> implementation, __cobalt() would force a call to the Cobalt >>>>>>>>>> implementation of the service. >>>>>>>>>> >>>>>>>>> Thanks for the clarification, will sprinkle the code with __STD(...) >>>>>>>>> and __RT(...), from here on :-). >>>>>>>>> >>>>>>>> >>>>>>>> That's only required if you want your code to unambiguously route to the >>>>>>>> proper service in case the default symbol wrapping does not fit, or is >>>>>>>> not present. This is typically what libcopperplate does, so that >>>>>>>> non-POSIX apps can link against it, without being required to wrap the >>>>>>>> POSIX symbols in the final executable. >>>>>>> >>>>>>> More to avoid me shooting myself in the foot when trying to juggle sockets >>>>>>> from two different domains (also makes the code less dependent on the linker >>>>>>> flags given). Already got bitten by 'modprobe rtpacket' not loading properly >>>>>>> and the __wrap_socket picking up the posix version. And of course making the >>>>>>> code clearly document what belongs where. >>>>>> >>>>>> Not loading rtpacket should cause __wrap_socket to use the posix >>>>>> version only if you are trying to create a socket type that the >>>>>> rtpacket module implements. Otherwise, this is a bug. >>>>> >>>>> And unless code has changed between 2.x and 3.x in this area, using >>>>> __RT() will result in exactly the same behaviour. >>>> >>>> You might be right, but AFAICT, on 2.6.2.1 'int __rt_dev_socket(...)' >>>> (ksrc/skins/rtdm/core.c) calls 'struct rtdm_device *get_protocol_device(...)' >>>> (ksrc/skins/rtdm/device.c), while in xenomai3/next 'COBALT_IMPL(int, socket,...)' >>>> does a 'XENOMAI_SYSCALL3(sc_cobalt_socket, ...)' and then does a failover to >>>> '_STD(socket, ...)' in case of -ENOSYS (which is what I believe an unloaded rt_packet.ko >>>> gives as a result). >>>> >>>> Am I missing something obvious? >>> >>> You are comparing user-space code with kernel space code. In xenomai >>> 2.6, the user-space code you should be looking at is >>> src/skins/posix/rtdm.c >> Even from native mode (which is what I use in 2.6)? > > In that case, you should look at src/skins/rtdm/core.c > The services rt_dev_socket belongs to the rtdm skin not to native > skin. I stand humbly corrected. > >> >>> And in that code __wrap_socket falls back to __real_socket if the >>> kernel-space code returns one of the known errors. >>> >>> Now the real question is: what arguments do you pass to the cobalt >>> rt socket call? If these arguments are the one corresponding to the >>> socket protocol implemented by the rtpacket module, the behaviour >>> you observe is normal, otherwise, this is a bug. >> I don't say it's a bug, but to me it seems like alchemy differs from >> the old native skin in this case. > > Well, not really, the native skin never had a socket call anyway, > and alchemy does not either. It is just that the rtdm skin > disappeared, so now you use the cobalt service instead of the rtdm > skin. # /usr/xenomai/bin/xeno-config --version 3.0-rc2 # usr/xenomai/bin/xeno-config --help Usage xeno-config OPTIONS Options : --help --v,--verbose --version --cc --ccld --arch --prefix --[skin=]posix/cobalt|vxworks|psos|alchemy|rtdm|smokey --rtdm is there, bug? Is there any way to check if a returned filedescriptor is a __RT or __STD one? /Anders -- Anders Blomdell Email: anders.blomdell@control.lth.se Department of Automatic Control Lund University Phone: +46 46 222 4625 P.O. Box 118 Fax: +46 46 138118 SE-221 00 Lund, Sweden