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[209.85.167.43]) by smtp.gmail.com with ESMTPSA id g24sm2813014lfh.90.2020.05.29.12.31.20 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 29 May 2020 12:31:21 -0700 (PDT) Received: by mail-lf1-f43.google.com with SMTP id 82so384361lfh.2 for ; Fri, 29 May 2020 12:31:20 -0700 (PDT) X-Received: by 2002:ac2:5a4c:: with SMTP id r12mr5203392lfn.10.1590780680343; Fri, 29 May 2020 12:31:20 -0700 (PDT) MIME-Version: 1.0 References: <20200514033104.kRFL_ctMQ%akpm@linux-foundation.org> <611fa14d-8d31-796f-b909-686d9ebf84a9@infradead.org> <20200528172005.GP2483@worktop.programming.kicks-ass.net> <20200529135750.GA1580@lst.de> <20200529143556.GE706478@hirez.programming.kicks-ass.net> <20200529145325.GB706518@hirez.programming.kicks-ass.net> <20200529153336.GC706518@hirez.programming.kicks-ass.net> <20200529160514.cyaytn33thphb3tz@treble> <20200529161253.GD706460@hirez.programming.kicks-ass.net> <20200529165011.o7vvhn4wcj6zjxux@treble> In-Reply-To: <20200529165011.o7vvhn4wcj6zjxux@treble> From: Linus Torvalds Date: Fri, 29 May 2020 12:31:04 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: mmotm 2020-05-13-20-30 uploaded (objtool warnings) To: Josh Poimboeuf Cc: Peter Zijlstra , Christoph Hellwig , Randy Dunlap , Andrew Morton , Mark Brown , linux-fsdevel , Linux Kernel Mailing List , Linux-MM , Linux Next Mailing List , Michal Hocko , mm-commits@vger.kernel.org, Stephen Rothwell , Al Viro , "the arch/x86 maintainers" , Steven Rostedt 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, May 29, 2020 at 9:50 AM Josh Poimboeuf wrote: > > From staring at the asm I think the generated code is correct, it's just > that the nested likelys with ftrace profiling cause GCC to converge the > error/success paths. But objtool doesn't do register value tracking so > it's not smart enough to know that it's safe. I'm surprised that gcc doesn't end up doing the obvious CSE and then branch following and folding it all away in the end, but your patch is obviously the right thing to do regardless, so ack on that. Al - I think this had best go into your uaccess cleanup branch with that csum-wrapper update, to avoid any unnecessary conflicts or dependencies. Linus From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92CC0C433DF for ; Fri, 29 May 2020 19:31:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2FE9D207D4 for ; Fri, 29 May 2020 19:31:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="GfHFxtgl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2FE9D207D4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 891768001A; Fri, 29 May 2020 15:31:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 83FAE80010; Fri, 29 May 2020 15:31:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7545B8001A; Fri, 29 May 2020 15:31:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0070.hostedemail.com [216.40.44.70]) by kanga.kvack.org (Postfix) with ESMTP id 5B38B80010 for ; Fri, 29 May 2020 15:31:26 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 0FC028248068 for ; Fri, 29 May 2020 19:31:26 +0000 (UTC) X-FDA: 76870750572.03.feet39_63c47208d8029 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin03.hostedemail.com (Postfix) with ESMTP id F01E728A4EE for ; Fri, 29 May 2020 19:31:25 +0000 (UTC) X-HE-Tag: feet39_63c47208d8029 X-Filterd-Recvd-Size: 4820 Received: from mail-lj1-f179.google.com (mail-lj1-f179.google.com [209.85.208.179]) by imf23.hostedemail.com (Postfix) with ESMTP for ; Fri, 29 May 2020 19:31:25 +0000 (UTC) Received: by mail-lj1-f179.google.com with SMTP id o9so643395ljj.6 for ; Fri, 29 May 2020 12:31:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=dHD8TmCoQhuoCHpObwNDm6CdH7YyaMO9+wxjMxR+Oh8=; b=GfHFxtgln7yqSB1se2pJ14wo3yKSKifw0tK/O3YykA6cZk6SnwfwCdJUoPGoBPoiuq hvt32o1ueibjeP164cZ8R3sMzIvfIcIo3+4N7mAY1YnFWCZTz7Mto7uPHUpOdH/n6kSA PX8IEjgVF+Qcx1Pu1z4J/EywIHY1OR/5PBRqM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=dHD8TmCoQhuoCHpObwNDm6CdH7YyaMO9+wxjMxR+Oh8=; b=EKoguaKfuh7wDDgwJKTgbSGWuv2bq61L90XcDOFrQtOy1loQ/MSOw4evnK8Ed+EPwW b9ypoFz1sut01TyxIzjP4+QnrLX6fKs7uMBJrAxjM2DkfIpBlrmjRwpdl9aPCRSr/esV fXtItRprJg11n74xY8vVzItMPOaXHYAMquOrwCBMm2Qd939Wy07HeKSFHsECX4cMnFDU aM6zwFVfYum8myu0eSb4NMZQnJmkju9nEep4WrbvrB9UspRlCXJFzElcVJjZMNtPAPQG ZoOvFqSBJs7Rl3gJV84uSKWbeFtEIFiLWXn5vunfVPEXtBCalkOgRaf2Uc7/N3wSrMPj UdYw== X-Gm-Message-State: AOAM530QxOjVZeUf3Hvurxnh4w1FvAcZcN9+ijVaUgnO441Xjgboy7mc 3tnknOV/qvPU9IZPis4ruKNvwaKK1UA= X-Google-Smtp-Source: ABdhPJwHMuoI3mXVRO96zW10r1c3l+aHPiFrEjWPR8GAeFxrP17MDpJl2uRFpM5LmBcy0Wy7vIDhiQ== X-Received: by 2002:a2e:8e25:: with SMTP id r5mr4774791ljk.455.1590780682690; Fri, 29 May 2020 12:31:22 -0700 (PDT) Received: from mail-lf1-f50.google.com (mail-lf1-f50.google.com. [209.85.167.50]) by smtp.gmail.com with ESMTPSA id g24sm2813013lfh.90.2020.05.29.12.31.20 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 29 May 2020 12:31:21 -0700 (PDT) Received: by mail-lf1-f50.google.com with SMTP id c21so379576lfb.3 for ; Fri, 29 May 2020 12:31:20 -0700 (PDT) X-Received: by 2002:ac2:5a4c:: with SMTP id r12mr5203392lfn.10.1590780680343; Fri, 29 May 2020 12:31:20 -0700 (PDT) MIME-Version: 1.0 References: <20200514033104.kRFL_ctMQ%akpm@linux-foundation.org> <611fa14d-8d31-796f-b909-686d9ebf84a9@infradead.org> <20200528172005.GP2483@worktop.programming.kicks-ass.net> <20200529135750.GA1580@lst.de> <20200529143556.GE706478@hirez.programming.kicks-ass.net> <20200529145325.GB706518@hirez.programming.kicks-ass.net> <20200529153336.GC706518@hirez.programming.kicks-ass.net> <20200529160514.cyaytn33thphb3tz@treble> <20200529161253.GD706460@hirez.programming.kicks-ass.net> <20200529165011.o7vvhn4wcj6zjxux@treble> In-Reply-To: <20200529165011.o7vvhn4wcj6zjxux@treble> From: Linus Torvalds Date: Fri, 29 May 2020 12:31:04 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: mmotm 2020-05-13-20-30 uploaded (objtool warnings) To: Josh Poimboeuf Cc: Peter Zijlstra , Christoph Hellwig , Randy Dunlap , Andrew Morton , Mark Brown , linux-fsdevel , Linux Kernel Mailing List , Linux-MM , Linux Next Mailing List , Michal Hocko , mm-commits@vger.kernel.org, Stephen Rothwell , Al Viro , "the arch/x86 maintainers" , Steven Rostedt Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: F01E728A4EE X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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 Fri, May 29, 2020 at 9:50 AM Josh Poimboeuf wrote: > > From staring at the asm I think the generated code is correct, it's just > that the nested likelys with ftrace profiling cause GCC to converge the > error/success paths. But objtool doesn't do register value tracking so > it's not smart enough to know that it's safe. I'm surprised that gcc doesn't end up doing the obvious CSE and then branch following and folding it all away in the end, but your patch is obviously the right thing to do regardless, so ack on that. Al - I think this had best go into your uaccess cleanup branch with that csum-wrapper update, to avoid any unnecessary conflicts or dependencies. Linus