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[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