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Tue, 03 Dec 2019 20:08:24 -0800 (PST) Received: from localhost ([2620:15c:6:12:9c46:e0da:efbf:69cc]) by smtp.gmail.com with ESMTPSA id b129sm5555207pfb.147.2019.12.03.20.08.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Dec 2019 20:08:23 -0800 (PST) Date: Tue, 3 Dec 2019 23:08:22 -0500 From: Joel Fernandes To: Steven Rostedt Cc: Primiano Tucci , Mathieu Desnoyers , Andrew Morton , aneesh kumar , Carmen Jackson , Dan Williams , Daniel Colascione , jglisse@redhat.com, linux-mm , Mayank Gupta , Michal Hocko , Minchan Kim , mm-commits@vger.kernel.org, rcampbell@nvidia.com, Tim Murray , Linus Torvalds , Vlastimil Babka , Matthew Wilcox Subject: Re: [patch 026/158] mm: emit tracepoint when RSS changes Message-ID: <20191204040822.GA192877@google.com> References: <20191201015030.MR-ux4mV1%akpm@linux-foundation.org> <20191202121415.1e64a461@gandalf.local.home> <20191202211345.GE17234@google.com> <20191202165601.42366c21@gandalf.local.home> <20191202234514.GR17234@google.com> <20191202185324.30b502bb@gandalf.local.home> <2084584347.3560.1575351504972.JavaMail.zimbra@efficios.com> <20191203105842.2e504fca@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20191203105842.2e504fca@gandalf.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Dec 03, 2019 at 10:58:42AM -0500, Steven Rostedt wrote: > On Tue, 3 Dec 2019 10:44:36 +0000 > Primiano Tucci wrote: >=20 > > Furthermore, from a pure technical viewpoint, dynamic linking is a ma= jor pain > > for many cross-platform projects because has different subtleties on = each > > platform. Most projects just ship big statically linked monoliths. > > Having a LGPL dependency in Perfetto means telling them "if you want = to use > > this tracing project you need to change your build rules / packaging = strategy > > and start dealing with dynamic linking on four different platforms > > (Linux, Android, Mac, Windows)". This would be a show-stopper for our > > project. > > >=20 > LGPL does not impose restrictions on having to be dynamically linked. > You can legally statically link a LGPL project as well. There's no > problem with that. You can do that with glibc too. I did know static link is Ok, thanks for clarifying that. >=20 > The one reason I can see that Google wouldn't want to include it, is > that you would also be required to maintain the library that you use. > That is, if someone wants the source code of the library you are using, > you must be able to provide it for them. That's the requirement that > LGPL imposes. >=20 > Now it is true that if someone wants to modify the LGPL library, enough > must be distributed to allow the user to do that. But as your code is > Apache, I'm guessing you can give people enough code to still do that. >=20 > From: https://copyleft.org/guide/comprehensive-gpl-guidech11.html#x14-1= 0100010.1 >=20 > "There are, however, subtle differences and additions. For example not > only is CCS required (as would be with normal versions of GPL), but > also the CCS provided must enable a developer to regenerate the > modified version of the entire combined work, using with a modified > version of the LGPL=E2=80=99d work (as a replacement for the version a > distributor provided). For example, LGPL=E2=80=99d code is statically = linked to > a non-copyleft executable, the required source code must also include > sufficient material to split the distributed executable and relink wit= h > a modified version of the library." >=20 > Thus, you are right that code licensed under LGPL is a "handle with > care". But there's a lot of code under LGPL, I'm surprised that there's > not better mechanisms to handle it. Actually, this is not the concern here. CCS should not be an issue for Perfetto since (AIUI) it is fully open source. Or, am I missing your poin= t? For fully open source projects, I don't think Google should have a proble= m with statically linking to LGPL. The only issue that can arise is if an Apache 2.0 project like Perfetto u= ses libtraceevent, but instead of statically linking to libtraceevent, it actually derives from libtraceevent. I think only this case it will be problematic, right? All other cases should be fine. thanks, - Joel > One solution I'm looking at is creating flex/bison templates to do the > parsing. If we do this, those could be licensed under a different > license that would make it easier for others to include this code. >=20 > -- Steve