From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4B73C421.1020200@domain.hid> Date: Thu, 11 Feb 2010 09:47:29 +0100 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <4B72A7E2.5020001@domain.hid> <4B72A9DA.1090104@domain.hid> <4B730A04.9040908@domain.hid> <4B731608.6010803@domain.hid> <4B73180C.6070301@domain.hid> <4B73207C.6020400@domain.hid> <4B73218A.9080306@domain.hid> <4B7323D5.1040804@domain.hid> <4B732487.50103@domain.hid> <4B732679.4030306@domain.hid> <4B73278F.9050603@domain.hid> <4B73C214.3010107@domain.hid> In-Reply-To: <4B73C214.3010107@domain.hid> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-core] [Xenomai-git] Jan Kiszka : Make xnarch_init_timeconv an uninlined weak function List-Id: Xenomai life and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Xenomai core Jan Kiszka wrote: > Gilles Chanteperdrix wrote: >> Jan Kiszka wrote: >>> Gilles Chanteperdrix wrote: >>>> Jan Kiszka wrote: >>>>> Gilles Chanteperdrix wrote: >>>>>> Jan Kiszka wrote: >>>>>>> Gilles Chanteperdrix wrote: >>>>>>>> Jan Kiszka wrote: >>>>>>>>> Gilles Chanteperdrix wrote: >>>>>>>>>> Jan Kiszka wrote: >>>>>>>>>>> Gilles Chanteperdrix wrote: >>>>>>>>>>>> GIT version control wrote: >>>>>>>>>>>>> Module: xenomai-jki >>>>>>>>>>>>> Branch: for-upstream >>>>>>>>>>>>> Commit: 6b40653e9c3c4a2433bb4e91344fc378eb860f75 >>>>>>>>>>>>> URL: http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=6b40653e9c3c4a2433bb4e91344fc378eb860f75 >>>>>>>>>>>>> >>>>>>>>>>>>> Author: Jan Kiszka >>>>>>>>>>>>> Date: Wed Feb 10 13:24:29 2010 +0100 >>>>>>>>>>>>> >>>>>>>>>>>>> Make xnarch_init_timeconv an uninlined weak function >>>>>>>>>>>>> >>>>>>>>>>>>> Otherwise the wrong set of time conversion variables might get >>>>>>>>>>>>> initialized when using > 1 skin libraries. >>>>>>>>>>>> If that would be possible, then it is the conversion variables which >>>>>>>>>>>> should made be weak, not the function. >>>>>>>>>>>> >>>>>>>>>>>> The way I see it, the posix and native skins currently get a different >>>>>>>>>>>> set of variables and functions, which works, but with your change, since >>>>>>>>>>>> there is only one function, only one set of variable gets initialized by >>>>>>>>>>>> the two function calls. And one skin just broke. >>>>>>>>>>>> >>>>>>>>>>>> Or am I missing something? Does the patch fix a problem you really had? >>>>>>>>>>> Frankly, I wasn't able to test in the field yet as replacing the libs >>>>>>>>>>> there is non-trivial. But I was able to observe that only one set of >>>>>>>>>>> functions is used - which is logical considering the weak marks. And >>>>>>>>>>> this breaks due to the static inline initialization. >>>>>>>>>>> >>>>>>>>>>> However, let's mark both functions and variables weak to fix the issue >>>>>>>>>>> and avoid leaving unused variables around. Will update my patch in a minute. >>>>>>>>>> Ok. I am reverting this patch until you provide me with another >>>>>>>>>> solution. It causes latency to segfault purely and simply at startup on >>>>>>>>>> my dual PIII. >>>>>>>>>> >>>>>>>>> Cannot reproduce yet. Do you have a backtrace? >>>>>>>> No. But the problem is probably the same as the one signaled by Henri, >>>>>>>> a misplaced weak directive ending up in a symbol with no address at all. >>>>>>>> Since the current situation works, I am going to wait for the "clean" >>>>>>>> fix which puts some code/data in the src/skins/common directory. >>>>>>>> >>>>>>> Find it in my tree. But it's not yet well tested. >>>>>> I do not like it either. Functions which are in src/skins/common should >>>>>> still be weak, since this lib is included in all the skins libraries. >>>>> Those functions are now in libxeno_common only, so I see no point in >>>>> allowing them to be overloaded. >>>> Yes, but libxeno_common is included in libpthread_rt.so and >>>> libnative.so. So, if you link with both libraries, you get >>>> libxeno_common twice. >>>> >>> Do we link libxeno_common statically? Otherwise, this conflict is not >>> logical to me. Also, there are other symbols in bind.c that are non-weak. >> libxeno_common is a "convenience library", which means that when >> libpthread_rt.so is assembled, the object files from libxeno_common are >> included. > > BTW, what speaks against making it a dynamic library? Complications. Currently the way of linking a native application is to do: `xeno-config --ldflags` -lnative Since when linking, the order matter, we can not hide this new library in xeno-config --ldflags, so we would have to turn this into: `xeno-config --ldflags` -lnative -lxeno-common i.e. breaking user way of building applications. I do not think the gain is worth the trouble: linking against only one xenomai library looks to me like the most common case. > >> I guess the loader eliminates the duplicates. >> > > It has to. For the same reason, we should be able to clean up > skins/common/current.c now. I am not that confident about that change. By using the weak directive, we make sure that the same __thread variable is used for instance. If we do not do that, what prevents the code from using the local symbols in each library ? IOW, removing the duplicate could work for libxeno_common symbols when invoked externally (which probably almost never happens), but not inside the skin libraries. I do not know about that, which is why I kept the weak declarations. -- Gilles.