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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A023CC433E0 for ; Wed, 22 Jul 2020 10:50:15 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 65A49207BB for ; Wed, 22 Jul 2020 10:50:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="3c6XYHK/"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="SIrZJLfl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 65A49207BB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=mA3hwEuqPagpuWU1N6PepmLxz19xP16VGmisLkd5gGk=; b=3c6XYHK/5X3p9H3IoS3ac8MIe r+OWPZL92gtB0Zxi/4Gm7a/cXZT4EzWk2+cPilyP0XHm/YdTo23xvIuJV19FIA4e1x//8fKoOTAsT IFckwRgOZOvKlm92O6iqqJ3mRFHA75kTVMCXemqzX4eQ4EGYerCdSlh+xvJyGPMiiIo2EQ6KU+ELc Ti07qf/g8HrfhJwxjTQ8UJi8hIR+cTsgl+ezY8Yp30uMXDrDdu+xESevt5yvYMNSaCgkLCcvSoTh/ uWQovpveiThYvpEYhscXtdbFjbCVNIkLy0oK8bJwb3uaTFosd7BtX21J9UebD7Zv4wnPtqw+vlut4 daWcaCQjQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyCIy-00019U-D2; Wed, 22 Jul 2020 10:48:56 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyCIv-00018e-QN for linux-arm-kernel@lists.infradead.org; Wed, 22 Jul 2020 10:48:54 +0000 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5EB1020787; Wed, 22 Jul 2020 10:48:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1595414933; bh=NIwzaWf5bZqnyx4UIr1FWoTafvSVnWWXNbEOWOA+zm0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SIrZJLfllDymBxhp0LdxHEFyR/jZKOmH3z3nnjQa/EWNHZazbfUMGeZrHMqtVIdgs HPFLPOVFYg8FC07r08TWokK7DahsJ3qQ/C4nesn/L3tDV2RlByU//NW7D4EyYdsRbA JRiD1/BVkqrdijy6Hg0g+sHKE6bIJeG/8aCLmZZU= Date: Wed, 22 Jul 2020 12:48:59 +0200 From: Greg KH To: Suzuki K Poulose Subject: Re: [PATCH v3 19/20] coresight: add try_get_module() in coresight_grab_device() Message-ID: <20200722104859.GA2827860@kroah.com> References: <20200717054536.7052-1-tingwei@codeaurora.org> <20200717054536.7052-20-tingwei@codeaurora.org> <7ef8d427-23c9-10cd-b337-03ae75476a8c@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <7ef8d427-23c9-10cd-b337-03ae75476a8c@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200722_064853_937444_4F2832AE X-CRM114-Status: GOOD ( 15.91 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: tsoni@codeaurora.org, saiprakash.ranjan@codeaurora.org, kim.phillips@arm.com, mathieu.poirier@linaro.org, alexander.shishkin@linux.intel.com, coresight@lists.linaro.org, rdunlap@infradead.org, ykaukab@suse.de, linux@armlinux.org.uk, jinlmao@codeaurora.org, tingwei@codeaurora.org, leo.yan@linaro.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jul 22, 2020 at 11:49:48AM +0100, Suzuki K Poulose wrote: > Hi Tingwei, > > On 07/17/2020 06:45 AM, Tingwei Zhang wrote: > > When coresight device is in an active session, driver module of > > that device should not be removed. Use try_get_module() in > > coresight_grab_device() to prevent module to be unloaded. > > > > Is this really sufficient ? AFAIU, a device could be removed, but the > module may still be alive due to the refcount on the module. This > could imply that we have stale pointers in the _path_, which could > lead to corruption elsewhere. Should we do a get/put_device() instead ? Remember there are two separate things here, code and data. There are two different reference counts for them, do not confuse the two. get/put is needed when you have a reference to the data, module stuff is when you are calling into code. But note that you do not always need to grab a reference count to the module, as long as the module can properly tear the data down when it is asked to be removed. Look at networking drivers as a great example of that. thanks, greg k-h _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel