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[209.85.208.175]) by smtp.gmail.com with ESMTPSA id s27sm3057102lfc.43.2019.11.01.11.49.04 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 01 Nov 2019 11:49:04 -0700 (PDT) Received: by mail-lj1-f175.google.com with SMTP id r7so2546531ljg.2 for ; Fri, 01 Nov 2019 11:49:04 -0700 (PDT) X-Received: by 2002:a05:651c:154:: with SMTP id c20mr9193922ljd.1.1572634144278; Fri, 01 Nov 2019 11:49:04 -0700 (PDT) MIME-Version: 1.0 References: <20191101174840.GA81963@gmail.com> In-Reply-To: <20191101174840.GA81963@gmail.com> From: Linus Torvalds Date: Fri, 1 Nov 2019 11:48:48 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] perf fixes To: Ingo Molnar Cc: Linux Kernel Mailing List , Peter Zijlstra , Arnaldo Carvalho de Melo , Jiri Olsa , Alexander Shishkin , Mark Rutland , Thomas Gleixner Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 1, 2019 at 10:48 AM Ingo Molnar wrote: > > Alexander Shishkin (1): > perf/core: Start rejecting the syscall with attr.__reserved_2 set This seems to quite possibly break existing apps. Is there any reason to believe that existing users have actually cleared that field? It's suspect for another reason too: the commit that added that field just added it to the end of the structure, with the argument that "aux_watermark will only matter for new AUX-aware code, so the old code should still be fine". So by *definition* those old kinds of users would never have cleared that field, because that field didn't exist. Honestly, this all shows a worrying complete disregard for backwards compatibility. Calling this a "fix" is questionable, when it is much more likely to break some old user. I've pulled it, but I need people to be aware that this is utter garbage, and that if anybody ever reports it, this needs to be immediately reverted. And the people involved should stop claiming this "fixes" anything, and should look hard at their random ABI expansions and "fixes". The original code that said "old users would not be impacted" is correct. But this "fix" is very very very questionable indeed, and I get the feeling that somebody doesn't understand what ABI is, when they claim that this "fixes" anything. Linus