From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout12.his.huawei.com (canpmsgout12.his.huawei.com [113.46.200.227]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D4728418A46 for ; Tue, 4 Aug 2026 09:38:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.227 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785836307; cv=none; b=jfatEI0I7vBzm/NmtB80I6e0d8cIXleiOa936enD1tTOAju/HGHalz+mxKtIE1Qn1uLhlKX0y1rh8w72mJ2a14idRlxao3ZjNwZjOHlq8FC5+DLxank4uprr+XItyoriZPXamZQVUWjM5Zimf9X9sxRpZqRNXdH62my9H8K808Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785836307; c=relaxed/simple; bh=sBgCGykOe4dGi+t75u3foiUNg9DJqcvnAqJThzQcG9s=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=urURuvDAwVCDdJZ0BCTINAS3CC7RlBdJjcD3w/PI0lPmbnufL9kJK28Di1mxVOWg2ttucMSr/76hLUdHbb+PTHPFxHU7vv87lOlCdRdjLiaTG6U3vuZ/AkkKqAuAFCH70KOF7TSMgqhW8DGBeE7LnveCnE05wmIxxIDfb8Dwc4Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=GhZ5aLEh; arc=none smtp.client-ip=113.46.200.227 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="GhZ5aLEh" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=i+ghQVwwIcBHPV3xBu7iUV/MUtzGz9ebQRM8ZIfeaVU=; b=GhZ5aLEhiFaCM3jklQpFSS7vF2SYu99iFO3h/0DiE9Kf1fOocwp5HQHZ8G4pyVbh5n91YEUbI lx32I4z4RVPQeyqxtN6HYN2brFFxdwwrv6yWAt+M7o8ditZyD925MauCivtVi/IxiCF6b1E6RmY WBb5YCrKatqS8jpX0YFv7jc= Received: from mail.maildlp.com (unknown [172.19.162.92]) by canpmsgout12.his.huawei.com (SkyGuard) with ESMTPS id 4hDp9g537BznTVn; Tue, 4 Aug 2026 17:27:51 +0800 (CST) Received: from kwepemf100001.china.huawei.com (unknown [7.202.181.215]) by mail.maildlp.com (Postfix) with ESMTPS id C180E40565; Tue, 4 Aug 2026 17:38:18 +0800 (CST) Received: from [10.67.121.90] (10.67.121.90) by kwepemf100001.china.huawei.com (7.202.181.215) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.36; Tue, 4 Aug 2026 17:38:18 +0800 Message-ID: Date: Tue, 4 Aug 2026 17:38:17 +0800 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 0/4] devfreq: Add refcounts for governor modules To: Jie Zhan , , , , , , CC: , , , , References: <20260729102348.3857779-1-zhanjie9@hisilicon.com> From: "zhenglifeng (A)" In-Reply-To: <20260729102348.3857779-1-zhanjie9@hisilicon.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To kwepemf100001.china.huawei.com (7.202.181.215) On 7/29/2026 6:23 PM, Jie Zhan wrote: > A governor module can be dynamically inserted or removed if compiled as a > kernel module. 'devfreq->governor' would become NULL if the governor > module is removed when it's in use. > > For user-friendliness, get and put the module refcount of a governor module > when it's in use. As a result, unloading a governor module in use returns > an error, e.g.: > > $ cat governor > performance > $ rmmod governor_performance > rmmod: ERROR: Module governor_performance is in use > > Note that this can't stop force unload, so it's more of a > user-friendliness improvement rather than strict protection. The > existing code that keeps devfreq working when 'devfreq->governor' is > NULL should still be there. > > Patch 1-3 clean up mutex with guards and factor out a common governor > setting function, so as to prepare for implementing governor reference > counting. They can be applied separately. > > Patch 4 adds the reference counting mechanism for devfreq governor > modules. > > This set is based on devfreq-next of 7.1-rc1. > > Changelog > --------- > v4: > - Patch 3: Return an error if starting new governor fails and restoring > old governor succeeds, such that the caller won't get misled. > > v3: > - Link: https://lore.kernel.org/all/20260519113251.3745140-1-zhanjie9@hisilicon.com/ > - Rework patch 4 to make the 'owner' field assignment optional in the > governor code. This prevents device-driver-bundled governors (such as > those in hisi_uncore_freq and tegra30-devfreq) from causing > self-reference issues that block module removal. Additionally, merge > patches 4 and 5 to clearly present the new 'owner' member alongside > its usage. > - Drop patch 6 because it's no longer needed since v2. > - Update commit logs of patch 3 and 4 to clarify background and > motivation. > - Pick up 2 tags from Yaxiong (thanks!). > - Trivial cleanups. > > v2: > - Link: https://lore.kernel.org/all/20260513093832.1645890-1-zhanjie9@hisilicon.com/ > - Rebase on devfreq-next of 7.1-rc1. > - Drop the patches related to the NULL pointer deference issue of > 'devfreq->governor', which has been solved and merged recently. > - Remove the dedicated mutex for 'devfreq_governor_list' because the > refcount changes don't depend on that. > - Some minor cleanups and fixes. > > v1: > - Link: https://lore.kernel.org/all/20260326123428.800407-1-zhanjie9@hisilicon.com/ > > Jie Zhan (4): > devfreq: Use mutex guard in governor_store() > devfreq: Use mutex guard in devfreq_add/remove_governor() > devfreq: Factor out devfreq_set_governor() > devfreq: Refcount governor modules while in use > > drivers/devfreq/devfreq.c | 185 +++++++++++----------- > drivers/devfreq/governor_passive.c | 1 + > drivers/devfreq/governor_performance.c | 1 + > drivers/devfreq/governor_powersave.c | 1 + > drivers/devfreq/governor_simpleondemand.c | 1 + > drivers/devfreq/governor_userspace.c | 1 + > include/linux/devfreq-governor.h | 11 ++ > 7 files changed, 112 insertions(+), 89 deletions(-) > LGTM. Reviewed-by: Lifeng Zheng