From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj2-f41.google.com (mail-pj2-f41.google.com [74.125.227.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 41FB13D0938 for ; Fri, 25 Sep 2026 14:04:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.227.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790345089; cv=none; b=ARB42VFQC8J2NlwUewFhDsXq5pMx8O7jxoEfJ2em7d1SKkvNnYHpS94EE1w5MwvIqLayGopa3YfD9rE04uFQeJmr/Rs15tsFe24QPLTXdivWMaFSoygkMqDItv2HV2yM+2lHFt6g8blzjUF9NLhbAn3FHLuN114mrxPEC2BXUZM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790345089; c=relaxed/simple; bh=bbmOrdULgI/qG6m5ZYiQCPi7tLPM/ObVmBPDGixfQGU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KRK4pwAs2zZ4nFceWUj2WiESxY9p03FJOTC3v6uBzvFFsFYqM+q9OlFXPQ7AxoHHdMtxq4XcfNzfbOH4HQbo9t+d2Osb0CPOGOE3bcsl0KRRQJutLs1BHjiTcM/ERPDaTdK5MnyT0z0ZtD/BtjLZkbTjJr4ZSDyCvRCX+X/zyno= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=roeck-us.net; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=bse5lbuq; arc=none smtp.client-ip=74.125.227.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=roeck-us.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bse5lbuq" Received: by mail-pj2-f41.google.com with SMTP id 98e67ed59e1d1-3a0bcdf41a3so335323a91.2 for ; Fri, 25 Sep 2026 07:04:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790345087; x=1790949887; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:sender:from:to:cc :subject:date:message-id:reply-to:content-type; bh=ovT80gQ2vK9hf0kYJwc2d02kOlcxj5fWOcjSmSVAXmQ=; b=bse5lbuq0gvMgc7TpvEmOoh8qKL22WNqcNpNIb+9sweumah+jqJod2zjEtJZjsMM3o huuG9V4aMgpuHXYYymjk0BdPWhfQShJ70wGOmsoSrSvp4D5hsZwsA/IQhkPe2w0jYUbH 3Zc4oXF8o6/9K2av+z5o5pg9d9wxnPbXrX1yt2EFxTTsHtqWW2W3sn+2+v4ZkpfPWetQ o6QJKR4LNC4vVsIqz6UEn02+KhgQEdMAcSLdXM7drHM4lg0JY7VbMH2OMmNqxzM5Ezy8 T904O4v6kL2Sb9z5kAxhynxfnYoS0eOvCrNomIRPDXMxqRan45P7EWx01DC0nVzlcu4L es/w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790345088; x=1790949888; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:sender:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=ovT80gQ2vK9hf0kYJwc2d02kOlcxj5fWOcjSmSVAXmQ=; b=2C7qSKb0P9QDiCw0pYVKG3u7B0+u14R1mj1NPFrW0EDXhJKdaqukRcj4jjS5CEc7Ye GZr43v2UDlCgOjavAOPfsOCrA8rvKjkr99yS4AwrP58ypBciuL9fasVCy104/sGGpj/f jdI3wzUjPNRPRy2Bv5UXHsnkknLe8ni+JC+UNrBD8yQBUsB7QT8C8mwFdv6nCvFHTGFW WH7xyra3VIj8oPTcMRBJJsFBbnCznIj2XUtZyfLrvJtesUw1UfoHm19uVfh8mCZ6xQU7 VL2JihQZVxgK/jyZih7bNc7N/Rcd7a5OSJwcII9LbRo6CsnPmX6Bu6OMYcLPZ9MKodow CAHw== X-Forwarded-Encrypted: i=1; AKwUvBw0HFPtXb85OoRO87ZVqxHtSkgRx0P9B+A6HOiw7m0S7cPggJh7vO4Aoid3jE5TwIqUbyaijjUcdcaFVRw=@vger.kernel.org X-Gm-Message-State: AFuF++kaGoB1gj6e51UnmTmr62zxmAydJ1PxIV/M78rZjfa40lWdu7tn 3yl2JtuIVCxc8M5JS+3lfU1BEqKelDwSOCPWAfODqcWCoJsO6vfIxTH9 X-Gm-Gg: AYBFou1CRidfovxYo0r0lRnVGX0Imz6vZhpt177nhBKeSwGLgJ2eGXnyAEZEyn5zpn0 JiKSdU0HpMWLSi9LibRBuHH8Mhk4WsugGfzyI5JGoVVPTJ/j/vw0R3W6rO2f4H5H+Xwi8vmU6Fr eP00cUWoqb/FZSYAAtz2oEVFlF/ZntiQZ3Lf2FQJE1Ch24Udw0fM0U9ILG8WFkEO3+zlrs2XLY3 MLrp5BrBZi7MV7Zf/pXVDr2NAkal2KSeQp3ziPOr1To/QwIko/vAnmNxjbtbV4QTYy0GQKE3y2Z qmyCtShuhomGUxLqLhg/01HNHu0LnfFKQWAWcxMAKqMws3afBOXwu6omG6+z/rvZDGcb3ZMONSV IEF9EjScnlZQ9e1cun6EKn3enK2AW0JxkgsAIE4GtjoqZjlLDQ2V0ym6cBRgnT30A7ceVWAcUKt LayAxgUxgtQOJ8uj5pc45ZTlWrxyvPozHSBW4C7tOHr52gM+gttak3MPxu9RO4NzoiGm0QQndxJ hq6a6qWm0aLZKuT8+jpeMQ= X-Received: by 2002:a17:90b:3908:b0:3a0:c276:1ecb with SMTP id 98e67ed59e1d1-3a0c276224amr1313125a91.15.1790345087406; Fri, 25 Sep 2026 07:04:47 -0700 (PDT) Received: from server.roeck-us.net ([2600:1700:e321:62f0:da43:aeff:fecc:bfd5]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a09773e7c3sm10983338a91.17.2026.09.25.07.04.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Sep 2026 07:04:46 -0700 (PDT) Sender: Guenter Roeck Date: Fri, 25 Sep 2026 07:04:46 -0700 From: Guenter Roeck To: Ricardo Neri Cc: david.nystrom@est.tech, linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, ricardo.neri@intel.com Subject: Re: [PATCH 2/3] hwmon: (coretemp) Read TjMax only when refreshing the temperature Message-ID: <94dc8122-d6d7-40b0-adde-5e0cd7b645e9@roeck-us.net> References: <20260924-coretemp-temp-fault-v1-0-1884f0ff97d5@linux.intel.com> <20260924-coretemp-temp-fault-v1-2-1884f0ff97d5@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260924-coretemp-temp-fault-v1-2-1884f0ff97d5@linux.intel.com> On Thu, Sep 24, 2026 at 07:33:21PM -0700, Ricardo Neri wrote: > show_temp() reads TjMax before checking whether the cached temperature is > still fresh, but consumes it only when recomputing that temperature. On a > cache hit the value is discarded. > > Discarding it is not free. On CPUs that report TjMax in > MSR_IA32_TEMPERATURE_TARGET, get_tjmax() returns the value it just read > without storing it in tdata->tjmax, so every call reads the MSR again. > That is a cross-CPU call whenever the CPU owning the sensor is not the > current one, and it is made while holding tdata->update_lock. > > Read TjMax where it is used. The value cannot go stale in the meantime: > bits 23:16 of MSR_IA32_TEMPERATURE_TARGET are read-only, and the register > is package-scoped, so every CPU of the package reads the same value. > > The temperature reported to userspace does not change. > > Signed-off-by: Ricardo Neri Applied. No need to resend this or the previous patch. Thanks, Guenter