From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9559DC004D4 for ; Thu, 19 Jan 2023 16:58:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230367AbjASQ61 (ORCPT ); Thu, 19 Jan 2023 11:58:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230427AbjASQ6I (ORCPT ); Thu, 19 Jan 2023 11:58:08 -0500 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 86D05677A9; Thu, 19 Jan 2023 08:58:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1674147482; x=1705683482; h=message-id:subject:from:to:cc:date:in-reply-to: references:mime-version; bh=LPC2X1IyUYqT3xMp2MnPgtVl8bSwFTiOdaClvXnl8yw=; b=YjR2GnmeCKg/sifiDmdAfYv7L7pbB1RhCzK2iN7uQUoBrGxpDdkspkAm aANQI+wPLa6hDwV5oY+eqt5+4KX8dvlVcilOvc7t/hBgZR/4y86yQDhHP ruPOc5cvxwbEmlSzroUg2hlkhj3CaX+ihAbxWGQM8slMMlnX1UX7DVHj9 xiRl7AzbsL8YypHAPftTgX/3GLUj+XgzGBlXbcKgv2ixIgWi9nllc88nS 78VMfp6fsoAIVpTC0+umi08KQ8Jv00sf64UkSQr0gTIiUCRIIbhEKe2R5 q7bLPu4Dj1UikSrh0lj4XP7p7QiMVR87oIkLGBkAJxlCwx3xJQ6HW5m1O g==; X-IronPort-AV: E=McAfee;i="6500,9779,10595"; a="327439928" X-IronPort-AV: E=Sophos;i="5.97,229,1669104000"; d="scan'208,223";a="327439928" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Jan 2023 08:58:01 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10595"; a="653454906" X-IronPort-AV: E=Sophos;i="5.97,229,1669104000"; d="scan'208,223";a="653454906" Received: from wardsamx-mobl.amr.corp.intel.com (HELO spandruv-desk1.amr.corp.intel.com) ([10.212.216.92]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Jan 2023 08:58:01 -0800 Message-ID: <33bb6a2a6b473d74c73a730671e6bd12c764bcd6.camel@linux.intel.com> Subject: Re: [PATCH v5 0/3] Thermal ACPI APIs for generic trip points From: srinivas pandruvada To: "Rafael J. Wysocki" Cc: Daniel Lezcano , "Zhang, Rui" , "linux-pm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "christophe.jaillet@wanadoo.fr" , "linux-acpi@vger.kernel.org" Date: Thu, 19 Jan 2023 08:58:01 -0800 In-Reply-To: References: <20230113180235.1604526-1-daniel.lezcano@linaro.org> <2627c37e07dce6b125d3fea3bf38a5f2407ad6a1.camel@intel.com> <5aabdd3010a02e361fbbe01f4af0e30d11f0ae6b.camel@linux.intel.com> <8547963350fb3bdb09a4693f0eb80c7199ab6f21.camel@linux.intel.com> <87627e1f-322c-a195-8ce6-8922d9787ff0@linaro.org> <340f3ecdaddb2c422dcbe3df712a082f333eab0d.camel@linux.intel.com> Content-Type: multipart/mixed; boundary="=-GbUfNslkOBgyVn/ErPpj" User-Agent: Evolution 3.42.4 (3.42.4-2.fc35) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-GbUfNslkOBgyVn/ErPpj Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit On Thu, 2023-01-19 at 13:17 +0100, Rafael J. Wysocki wrote: > On Thu, Jan 19, 2023 at 12:04 AM srinivas pandruvada > wrote: > > > > On Wed, 2023-01-18 at 23:14 +0100, Daniel Lezcano wrote: > > > On 18/01/2023 22:16, srinivas pandruvada wrote: > > > > On Wed, 2023-01-18 at 22:01 +0100, Daniel Lezcano wrote: > > > > > On 18/01/2023 21:53, srinivas pandruvada wrote: > > > > > > On Wed, 2023-01-18 at 21:00 +0100, Daniel Lezcano wrote: > > > > > > > On 18/01/2023 20:16, srinivas pandruvada wrote: > > > > > > > > > > > > > > [ ... ] > > > > > > > > > > > > > > > > > But we'd better wait for the thermald test result > > > > > > > > > > from > > > > > > > > > > Srinvias. > > > > > > > > > > > > > > > > > > A quick test show that things still work with > > > > > > > > > thermald > > > > > > > > > and > > > > > > > > > these > > > > > > > > > changes. > > > > > > > > > > > > > > > > But I have a question. In some devices trip point > > > > > > > > temperature > > > > > > > > is > > > > > > > > not > > > > > > > > static. When hardware changes, we get notification. For > > > > > > > > example > > > > > > > > INT3403_PERF_TRIP_POINT_CHANGED for INT3403 drivers. > > > > > > > > Currently get_trip can get the latest changed value. > > > > > > > > But if > > > > > > > > we > > > > > > > > preregister, we need some mechanism to update them. > > > > > > > > > > > > > > When the notification INT3403_PERF_TRIP_POINT_CHANGED > > > > > > > happens, we > > > > > > > call > > > > > > > int340x_thermal_read_trips() which in turn updates the > > > > > > > trip > > > > > > > points. > > > > > > > > > > > > > > > > > > > Not sure how we handle concurrency here when driver can > > > > > > freely > > > > > > update > > > > > > trips while thermal core is using trips. > > > > > > > > > > Don't we have the same race without this patch ? The thermal > > > > > core > > > > > can > > > > > call get_trip_temp() while there is an update, no ? > > > > Yes it is. But I can add a mutex locally here to solve. > > > > But not any longer. > > > > > > > > I think you need some thermal_zone_read_lock/unlock() in core, > > > > which > > > > can use rcu. Even mutex is fine as there will be no contention > > > > as > > > > updates to trips will be rare. > > > > > > I was planning to provide a thermal_trips_update(tz, trips) and > > > from > > > there handle the locking. > > > > > > As the race was already existing, can we postpone this change > > > after > > > the > > > generic trip points changes? > > I think so. > > Well, what if this bug is reported by a user and a fix needs to be > backported to "stable"? > > Are we going to backport the whole framework redesign along with it? > > Or is this extremely unlikely? These trips are read at the start of DTT/Thermald and will be read once after notification is received. So extremely unlikely. But we can add the patch before this series to address this issue, which can be marked stable. I can submit this. 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