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 62C0BC6FD1D for ; Thu, 30 Mar 2023 14:01:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231935AbjC3OBP (ORCPT ); Thu, 30 Mar 2023 10:01:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230035AbjC3OBL (ORCPT ); Thu, 30 Mar 2023 10:01:11 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D99CE6EB8 for ; Thu, 30 Mar 2023 07:01:09 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CFE5F12FC; Thu, 30 Mar 2023 07:01:53 -0700 (PDT) Received: from [10.57.54.53] (unknown [10.57.54.53]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A35533F663; Thu, 30 Mar 2023 07:01:07 -0700 (PDT) Message-ID: Date: Thu, 30 Mar 2023 15:01:06 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH v3 06/13] coresight: Fix loss of connection info when a module is unloaded From: Suzuki K Poulose To: James Clark , coresight@lists.linaro.org, quic_jinlmao@quicinc.com, mike.leach@linaro.org Cc: Mathieu Poirier , Leo Yan , Alexander Shishkin , Maxime Coquelin , Alexandre Torgue , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com References: <20230329115329.2747724-1-james.clark@arm.com> <20230329115329.2747724-7-james.clark@arm.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/03/2023 13:42, Suzuki K Poulose wrote: > Hi James > > On 29/03/2023 12:53, James Clark wrote: >> child_fwnode should be a read only property based on the DT. If it's >> cleared on the parent device when a child is unloaded, then when the >> child is loaded again the connection won't be remade. >> >> child_dev should be cleared instead which signifies that the connection >> should be remade when the child_fwnode registers a new coresight_device. >> >> Similarly the reference count shouldn't be decremented as long as the >> parent device exists. The correct place to drop the reference is in >> coresight_release_platform_data() which is already done. >> >> Signed-off-by: James Clark > > This looks like a bug in the existing driver. Please could you keep this > at the beginning of the series, so that it is easier to backport for > stable ? > > Also, please add : > > Fixes: 37ea1ffddffa ("coresight: Use fwnode handle instead of device > names") > Fixes: 2af89ebacf29 ("coresight: Clear the connection field properly") > > >> --- >>   drivers/hwtracing/coresight/coresight-core.c | 10 ++-------- >>   1 file changed, 2 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/hwtracing/coresight/coresight-core.c >> b/drivers/hwtracing/coresight/coresight-core.c >> index bfe1b93aca4e..12cbb68e8e1c 100644 >> --- a/drivers/hwtracing/coresight/coresight-core.c >> +++ b/drivers/hwtracing/coresight/coresight-core.c >> @@ -1414,13 +1414,8 @@ static int coresight_remove_match(struct device >> *dev, void *data) >>           if (csdev->dev.fwnode == conn->dest_fwnode) { >>               iterator->orphan = true; >>               coresight_remove_links(iterator, conn); >> -            /* >> -             * Drop the reference to the handle for the remote >> -             * device acquired in parsing the connections from >> -             * platform data. >> -             */ >> -            fwnode_handle_put(conn->dest_fwnode); >> -            conn->dest_fwnode = NULL; >> + >> +            conn->dest_dev = NULL; >>               /* No need to continue */ >>               break; >>           } >> @@ -1553,7 +1548,6 @@ void coresight_release_platform_data(struct >> coresight_device *csdev, >>            * is going away >>            */ >>           fwnode_handle_put(conns[i].dest_fwnode); >> -        pdata->out_conns[i].dest_fwnode = NULL; > > This change is not required, as we are freeing the pdata anyway. > Keeping this might be beneficial if someone else comes looking > for references while we are going out. I don't see how we could > hit that, but just to be safe. For reference, I could reproduce the problem by : On juno, load all coresight modules. $ cd /sys/bus/coresight/devices/ $ echo 1 > tmc_etr0/enable_sink $ echo 1 > etm0/enable_source Works fine ^ $ echo 0 > etm0/enable_source $ rmmod coresight-funnel $ modprobe coresight-funnel $ echo 1 > etm0/enable_source -bash: echo: write error: Invalid argument Suzuki > > Suzuki >