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Thu, 13 Aug 2020 07:37:33 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id A93B8C433A0; Thu, 13 Aug 2020 07:37:32 +0000 (UTC) Received: from codeaurora.org (unknown [180.166.53.21]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: tingwei) by smtp.codeaurora.org (Postfix) with ESMTPSA id 05D29C433C6; Thu, 13 Aug 2020 07:37:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 05D29C433C6 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=tingweiz@codeaurora.org Date: Thu, 13 Aug 2020 15:37:20 +0800 From: Tingwei Zhang To: Mathieu Poirier Subject: Re: [PATCH v8 06/24] coresight: add try_get_module() in coresight_grab_device() Message-ID: <20200813073720.GA10706@codeaurora.org> References: <20200807111153.7784-1-tingwei@codeaurora.org> <20200807111153.7784-7-tingwei@codeaurora.org> <20200812193612.GE3393195@xps15> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200812193612.GE3393195@xps15> User-Agent: Mutt/1.5.24 (2015-08-30) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200813_033738_597927_36F436D5 X-CRM114-Status: GOOD ( 37.15 ) 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, Sai Prakash Ranjan , Kim Phillips , Mao Jinlong , Suzuki K Poulose , Alexander Shishkin , Greg Kroah-Hartman , coresight@lists.linaro.org, Randy Dunlap , Mian Yousaf Kaukab , Russell King , Tingwei Zhang , Leo Yan , linux-arm-kernel@lists.infradead.org, Mike Leach 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 Thu, Aug 13, 2020 at 03:36:12AM +0800, Mathieu Poirier wrote: > On Fri, Aug 07, 2020 at 07:11:35PM +0800, 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. > > Use get_device()/put_device() to protect device data > > in the middle of active session. > > > > Signed-off-by: Tingwei Zhang > > Tested-by: Mike Leach > > Suggested-by: Suzuki K Poulose > > --- > > drivers/hwtracing/coresight/coresight.c | 61 ++++++++++++++++++++++--- > > 1 file changed, 54 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/hwtracing/coresight/coresight.c > b/drivers/hwtracing/coresight/coresight.c > > index b7151c5f81b1..0b0e31577b9b 100644 > > --- a/drivers/hwtracing/coresight/coresight.c > > +++ b/drivers/hwtracing/coresight/coresight.c > > @@ -634,13 +634,45 @@ struct coresight_device > *coresight_get_sink_by_id(u32 id) > > return dev ? to_coresight_device(dev) : NULL; > > } > > > > +/** > > + * coresight_get_ref- Helper function to increase reference count to > module > > + * and device. > > + * Return true in successful case and power up the device. > > + * Return false when failed to get reference of module. > > + */ > > +static inline bool coresight_get_ref(struct coresight_device *csdev) > > +{ > > + struct device *dev = csdev->dev.parent; > > + > > + /* Make sure the driver can't be removed */ > > + if (!try_module_get(dev->driver->owner)) > > + return false; > > + /* Make sure the device can't go away */ > > + get_device(dev); > > + pm_runtime_get_sync(dev); > > + return true; > > +} > > + > > +/** > > + * coresight_put_ref- Helper function to decrease reference count to > module > > + * and device. Power off the device. > > + */ > > +static inline void coresight_put_ref(struct coresight_device *csdev) > > +{ > > + struct device *dev = csdev->dev.parent; > > + > > + pm_runtime_put(dev); > > + put_device(dev); > > + module_put(dev->driver->owner); > > +} > > + > > /* > > * coresight_grab_device - Power up this device and any of the helper > > * devices connected to it for trace operation. Since the helper > devices > > * don't appear on the trace path, they should be handled along with > the > > * the master device. > > */ > > -static void coresight_grab_device(struct coresight_device *csdev) > > +static int coresight_grab_device(struct coresight_device *csdev) > > { > > int i; > > > > @@ -649,9 +681,20 @@ static void coresight_grab_device(struct > coresight_device *csdev) > > > > child = csdev->pdata->conns[i].child_dev; > > if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) > > - pm_runtime_get_sync(child->dev.parent); > > + if (!coresight_get_ref(child)) > > + goto err; > > + } > > + if (coresight_get_ref(csdev)) > > + return 0; > > +err: > > + for (i--; i >= 0; i--) { > > + struct coresight_device *child; > > + > > + child = csdev->pdata->conns[i].child_dev; > > + if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) > > + coresight_put_ref(child); > > } > > - pm_runtime_get_sync(csdev->dev.parent); > > + return -ENODEV; > > } > > > > /* > > @@ -662,13 +705,13 @@ static void coresight_drop_device(struct > coresight_device *csdev) > > { > > int i; > > > > - pm_runtime_put(csdev->dev.parent); > > + coresight_put_ref(csdev); > > for (i = 0; i < csdev->pdata->nr_outport; i++) { > > struct coresight_device *child; > > > > child = csdev->pdata->conns[i].child_dev; > > if (child && child->type == CORESIGHT_DEV_TYPE_HELPER) > > - pm_runtime_put(child->dev.parent); > > + coresight_put_ref(child); > > } > > } > > > > @@ -687,7 +730,7 @@ static int _coresight_build_path(struct > coresight_device *csdev, > > struct coresight_device *sink, > > struct list_head *path) > > { > > - int i; > > + int i, ret; > > bool found = false; > > struct coresight_node *node; > > > > @@ -721,7 +764,11 @@ static int _coresight_build_path(struct > coresight_device *csdev, > > if (!node) > > return -ENOMEM; > > > > - coresight_grab_device(csdev); > > + ret = coresight_grab_device(csdev); > > I suggest trying to grab the device before allocating memory for the node. > If > grabing the device fails memory doesn't have to be allocated and released > needlessly. > Agree. I'll fix in next revision. Thanks, Tingwei > I will likely come back to this patch later after reviewing the rest the > this > set. > > Thanks, > Mathieu > > > + if (ret) { > > + kfree(node); > > + return ret; > > + } > > node->csdev = csdev; > > list_add(&node->link, path); > > > > -- > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora > Forum, > > a Linux Foundation Collaborative Project > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel