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[209.85.128.45]) by smtp.gmail.com with ESMTPSA id a8sm1345403eju.52.2019.02.15.09.24.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 15 Feb 2019 09:24:24 -0800 (PST) Received: by mail-wm1-f45.google.com with SMTP id h22so7123127wmb.0 for ; Fri, 15 Feb 2019 09:24:24 -0800 (PST) X-Received: by 2002:a7b:cb18:: with SMTP id u24mr6921394wmj.138.1550251096655; Fri, 15 Feb 2019 09:18:16 -0800 (PST) MIME-Version: 1.0 References: <20190213140025.GB6346@brain-police> <20190213142524.GW32494@hirez.programming.kicks-ass.net> <20190213144145.GY32494@hirez.programming.kicks-ass.net> <20190213154532.GQ32534@hirez.programming.kicks-ass.net> <20190213222146.GC32494@hirez.programming.kicks-ass.net> <20190214101429.GD32494@hirez.programming.kicks-ass.net> <20190214193432.GR32477@hirez.programming.kicks-ass.net> In-Reply-To: <20190214193432.GR32477@hirez.programming.kicks-ass.net> From: Linus Torvalds Date: Fri, 15 Feb 2019 09:18:00 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] sched/x86: Save [ER]FLAGS on context switch To: Peter Zijlstra X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190215_092427_164632_76B1875E X-CRM114-Status: GOOD ( 11.50 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Denys Vlasenko , Josh Poimboeuf , Julien Thierry , Brian Gerst , "H. Peter Anvin" , Will Deacon , Linux Kernel Mailing List , Andy Lutomirski , valentin.schneider@arm.com, Ingo Molnar , James Morse , Andy Lutomirski , Catalin Marinas , Borislav Petkov , Thomas Gleixner , Ingo Molnar , "linux-alpha@vger.kernel.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Feb 14, 2019 at 11:34 AM Peter Zijlstra wrote: > > Something like the below, right? > > + frame->flags = 0; > + frame->flags = 0; Those are not valid flag values. Can you popf them? Yes. Do they make sense? No. It has the IF flag clear, for example. Is that intentional? If it is, it should likely be documented. Because IF clear means "interrupts disabled". Are the places that load flags in irq disabled regions? Maybe they are, maybe they aren't, but shouldn't this be something that is made explicit, rather than "oh, let's initialize to zero like all the other registers we don't care about". Because a zero initializer for eflags really is odd. Linus _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel