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[209.85.208.173]) by smtp.gmail.com with ESMTPSA id w24sm2777211lfe.58.2020.04.21.12.03.26 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Apr 2020 12:03:27 -0700 (PDT) Received: by mail-lj1-f173.google.com with SMTP id l19so12627767lje.10 for ; Tue, 21 Apr 2020 12:03:26 -0700 (PDT) X-Received: by 2002:a2e:1418:: with SMTP id u24mr14588814ljd.265.1587495806435; Tue, 21 Apr 2020 12:03:26 -0700 (PDT) MIME-Version: 1.0 References: <428bac87-b6dd-0867-c8f8-622cd606de3e@skogtun.org> In-Reply-To: <428bac87-b6dd-0867-c8f8-622cd606de3e@skogtun.org> From: Linus Torvalds Date: Tue, 21 Apr 2020 12:03:10 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [BISECTED]: Kernel panic (was: Linux 5.7-rc2) To: Harald Arnesen , Peter Zijlstra , Ingo Molnar , "Rafael J. Wysocki" Cc: Linux Kernel Mailing List , Giovanni Gherdovich 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 Mon, Apr 20, 2020 at 1:52 AM Harald Arnesen wrote: > > Neither rc1 nor rc2 will boot on my laptop. The attached picture is all > I have been able to capture. I know you saw the reply about this probably being fixed by https://lore.kernel.org/lkml/20200416054745.740-1-ggherdovich@suse.cz/ but it would be lovely if you could actually verify that that series of four patches does indeed fix it for you. Your oops is on that divide instruction: freq_scale = div64_u64(acnt, mcnt); and while we had a check for mcnt not being zero earlier, we did mcnt *= arch_max_freq_ratio; after that check. I could see it becoming zero either due to an overflow, or due to arch_max_freq_ratio being 0. I think the first commit in that series is supposed to fix that arch_max_freq_ratio being 0 case, but it still feels like the code that does the divide is checking for zero in the wrong place... Linus