From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.tuxdriver.com (charlotte.tuxdriver.com [70.61.120.58]) by dpdk.org (Postfix) with ESMTP id 089951B8B4; Fri, 8 Feb 2019 16:38:16 +0100 (CET) Received: from cpe-2606-a000-111b-405a-9816-2c85-c514-8f7a.dyn6.twc.com ([2606:a000:111b:405a:9816:2c85:c514:8f7a] helo=localhost) by smtp.tuxdriver.com with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.63) (envelope-from ) id 1gs8EC-00084r-Tc; Fri, 08 Feb 2019 10:38:11 -0500 Date: Fri, 8 Feb 2019 10:37:40 -0500 From: Neil Horman To: Bruce Richardson Cc: dev@dpdk.org, stable@dpdk.org, David Marchand , Anatoly Burakov Message-ID: <20190208153740.GC13299@hmswarspite.think-freely.org> References: <20190110111104.56464-1-bruce.richardson@intel.com> <20190206110130.55135-1-bruce.richardson@intel.com> <20190206122254.GA16887@hmswarspite.think-freely.org> <20190206141744.GA236864@bricha3-MOBL.ger.corp.intel.com> <20190207143426.GA23613@hmswarspite.think-freely.org> <20190207150328.GA121112@bricha3-MOBL.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190207150328.GA121112@bricha3-MOBL.ger.corp.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Spam-Score: -2.9 (--) X-Spam-Status: No Subject: Re: [dpdk-dev] [PATCH v3] compat: merge compat library into EAL X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 08 Feb 2019 15:38:16 -0000 On Thu, Feb 07, 2019 at 03:03:28PM +0000, Bruce Richardson wrote: > On Thu, Feb 07, 2019 at 09:34:26AM -0500, Neil Horman wrote: > > On Wed, Feb 06, 2019 at 02:17:45PM +0000, Bruce Richardson wrote: > > > On Wed, Feb 06, 2019 at 07:22:54AM -0500, Neil Horman wrote: > > > > On Wed, Feb 06, 2019 at 11:01:30AM +0000, Bruce Richardson wrote: > > > > > Since compat library is only a single header, we can easily move it into > > > > > the EAL common headers instead of tracking it separately. The downside of > > > > > this is that it becomes a little more difficult to have any libs that are > > > > > built before EAL depend on it. Thankfully, this is not a major problem as > > > > > the only library which uses rte_compat.h and is built before EAL (kvargs) > > > > > already has the path to the compat.h header file explicitly called out as > > > > > an include path. > > > > > > > > > > However, to ensure that we don't hit problems later with this, we can add > > > > > EAL common headers folder to the global include list in the meson build > > > > > which means that all common headers can be safely used by all libraries, no > > > > > matter what their build order. > > > > > > > > > This assumes that the compat lib will always just be a header though, no? Will > > > > this work in the event that someone wants to add some compatibility code that > > > > requires its own C compilation unit? > > > > > > > > > > No, it probably won't work, you'll hit an issue with any libraries that > > > don't depend on EAL and need that functionality. The question is whether > > > this is likely to be an issue in the future for us. I'd say the possiblity > > > is fairly remote, but I'm open to input on it. > > > > > Im afraid I don't have any more visibility on that than anyone else. The fact > > that it hasn't been needed yet is likely a good sign, but I am concerned at the > > notion that this change enjoins us from having that flexibility. > > > Yes. However, in general is it not the case that compatibility code belongs > in the actual library wanting to provide the compatibility? That is what > has been done up till now. If we do need compatibility code placed more > centrally, I think EAL is as good a place for it as any - the only library > which doesn't depend on EAL now is kvargs, so our risk area is pretty low, > I think. > > Also, if we do need a compat libraries with .c files in it, there is no > reason we can't undo this change. It would be no more user visible than > adding a .c file to the existing structure, given that in both cases an > extra .so file will appear in the build output. > If the consensus is that compat code can all live in the EAL library, then I'm ok with it, even if its C code. The only thing I don't want is for our plan to be, in the event we need C code, to immediately undo this change. That just doesn't make sense to me. So, if you're ok with compat C code in eal, then Acked-by: Neil Horman > > > > > As a side-effect, this patch also fixes an issue with building on BSD using > > > > > meson, due to compat lib no longer needing to be listed as a dependency. > > > > > > > > > Can you elaborate here a bit please? listing a lib as a dependency seems like a > > > > fundamental function of a build system, was there a bug with meson in this > > > > capacity? > > > > > > > > > > It was a bug in DPDK. There was already a dependency on the compat > > > library from libeal from linux, but not from BSD, so when a further > > > dependency was added globally, the BSD build broke, but the linux one > > > didn't. > > > > > Do you have a link to the breakage details? I'd like to look at it to see if > > there is a way around this without enjoining us from adding compat C files in > > the future. > > > > Don't have a link handy, but the basics, as I understand them are as below: > > Commit a8499f65a1d1 ("log: add missing experimental tag"), added the > experimental tag to a log function. To get this tag definition rte_compat.h > header was included in the rte_log.h file in the "common" EAL folder. In > build tests on linux, this was no problem since linuxapp/eal/meson.build had the line: > eal_inc += include_directories('include', '../../../librte_compat') > However, the BSD eal/meson.build file did not have this line, giving a > compiler error. > > /Bruce > > PS: Now that I also look at the files more closely, with this move to put > compat.h into EAL, we can probably remove the special case processing in > lib/meson.build for libraries with an empty source array. > >