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Received: from sea.source.kernel.org ([172.234.252.31]) by desiato.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uw0VA-00000005PCQ-1QqP for linux-arm-kernel@lists.infradead.org; Tue, 09 Sep 2025 15:43:26 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 88F5942B8A; Tue, 9 Sep 2025 15:43:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D895C4CEF4; Tue, 9 Sep 2025 15:43:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757432600; bh=wx46RmInQBllen7vvy9mVav9mLQG3txkNO3EJHVEvcU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=dPi99mWizZ4GNWGio+Cx3ReKJsgOQhxqHUddhYBs6+l0lkcCadpOslzYOf3z/4cNz zBOS9eSjTqtkit+BHOwsKxf8Bkior7YZjugsdm2AcKnF4ooQQLAgaeqKQHwL2OOeEB 4PsCNMVx/w33aGRjlTr7qw7zkSOoliARNoyrc2v/XZmePm2vZVtrx/+pT1/SMWMbF8 i2uD/6v80E2qQq/CrbjuEH9V0neKWm9Sg6uB7QPTy5Oz/SSK5bc3XetOofsBtLbHJD ii3cpsK6ojuZkP6ydSjha+l+rOX8iyRzhk8YM1gV40IULNNsHKVMoZuWuHGmQHi6uQ 07umqE6d/ov9Q== Message-ID: <52222467-4fc0-4a53-9682-a935ec8f1a44@kernel.org> Date: Tue, 9 Sep 2025 17:43:16 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] soc: samsung: exynos-pmu: Fix for CONFIG_DEBUG_PREEMPT To: Will Deacon Cc: Mostafa Saleh , linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org, alim.akhtar@samsung.com, Peter Griffin , =?UTF-8?Q?Andr=C3=A9_Draszik?= References: <20250905162446.88987-1-smostafa@google.com> <19a6f296-eb40-49cf-9571-2d7964cd3313@kernel.org> <84332e77-cfd2-4090-a3c0-114a9eb5422a@kernel.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250909_164325_004235_5520A6E7 X-CRM114-Status: GOOD ( 25.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 09/09/2025 12:15, Will Deacon wrote: > Krzysztof, > > On Sat, Sep 06, 2025 at 09:07:02AM +0200, Krzysztof Kozlowski wrote: >> On 05/09/2025 19:43, Mostafa Saleh wrote: >>>>> >>>>> As this value is only read once, it doesn't require to be stable, so >>>> >>>> Why it does not need to be stable? Onlining wrong CPU number is not >>>> desired... >>>> >>>>> just use "raw_smp_processor_id" instead. >>>> >>>> You might be just hiding some other real issue, because above stacktrace >>>> is from gs101_cpuhp_pmu_online() which IRQs disabled and preemption >>>> disabled. Provide analysis of the warning, instead of just making it >>>> disappear. >>> >>> Not sure I understand, how is preemption disabled? that wouldn't fire >>> in that case. >> >> Because there is explicit preempt_disable(). > > Where do you see that? I did look at the code. All the calls I saw (including calltrace from commit msg) were under raw spinlock and raw spinlock does: preempt_disable(); > > From what I can tell, the driver (somewhat bizarrely) registers its > online callback much earlier (at CPUHP_BP_PREPARE_DYN) than the offline > callback so that gs101_cpuhp_pmu_online() will be run in the context of > the caller/onliner rather than the actual CPU coming up. I don't see > anything which disables preemption on that path. > >> So far you did not present any code analysis, any actual arguments, so >> deflecting reviewer's comment like above will get you nowhere. Instead >> of replying with a question, bring arguments that the code path does not >> disable the preemption. > > Mostafa's reported a bug and had a go at fixing it, for goodness sake. > Would you rather not hear about bugs in the code you maintain? I am happy to see such patch, but Mostafa instead of replying with anything useful just shoved back my comment back to me. > > As somebody who should understand this code better than most, perhaps > you could try a bit harder to fill in the blanks on the technical side I did and I investigated the code and I cannot find the issue leading to it, thus I asked. And then contributor just replied whatever so I will go away and stop bothering them? > rather than pointing out extraneous blank lines and making questionable > judgements about CC lines. > >> My call is that you run all this on some other kernel, just like usually >> happens in Google. > > Whilst that inevitably happens with some of the more product-facing > teams, I think it's foolish to assume that nobody works directly with > upstream at Google. We're also not going to waste time fabricating bug I saw many, many bug reports from Google and Linaro done on Android kernel. Really, too many. > reports which is why we bother to reproduce issues on Pixel 6, as that > can boot upstream without any additional patches. Best regards, Krzysztof