From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <54D8EB13.2000307@xenomai.org> Date: Mon, 09 Feb 2015 18:14:59 +0100 From: Philippe Gerum 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> <54D8E83F.6020601@control.lth.se> In-Reply-To: <54D8E83F.6020601@control.lth.se> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit 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: Anders Blomdell , Gilles Chanteperdrix Cc: "Xenomai@xenomai.org" On 02/09/2015 06:02 PM, Anders Blomdell wrote: > 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? > --rtdm --kcflags can be used in x3 for retrieving the kernel CFLAGS for building a RTDM driver. --rtdm --cflags just returns the same as --posix --cflags. > Is there any way to check if a returned filedescriptor is a __RT or __STD one? > Not using the old 2.x trick of testing the value. RTDM fildes are mere Linux ones now. Any RTDM fildes will answer the ioctl(RTIOC_DEVICE_INFO) request, non-RTDM ones won't. -- Philippe.