From patchwork Thu Nov 8 18:07:11 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Duyck X-Patchwork-Id: 10674819 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 29D3414BD for ; Thu, 8 Nov 2018 18:07:14 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1C29F2DE5F for ; Thu, 8 Nov 2018 18:07:14 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1021E2DE67; Thu, 8 Nov 2018 18:07:14 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 8592C2DE5F for ; Thu, 8 Nov 2018 18:07:13 +0000 (UTC) Received: from [127.0.0.1] (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 7960D2118DC52; Thu, 8 Nov 2018 10:07:13 -0800 (PST) X-Original-To: linux-nvdimm@lists.01.org Delivered-To: linux-nvdimm@lists.01.org Received-SPF: None (no SPF record) identity=mailfrom; client-ip=192.55.52.43; helo=mga05.intel.com; envelope-from=alexander.h.duyck@linux.intel.com; receiver=linux-nvdimm@lists.01.org Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 78001203B99BB for ; Thu, 8 Nov 2018 10:07:11 -0800 (PST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 08 Nov 2018 10:07:11 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,480,1534834800"; d="scan'208";a="106592093" Received: from ahduyck-desk1.jf.intel.com ([10.7.198.76]) by orsmga001.jf.intel.com with ESMTP; 08 Nov 2018 10:07:11 -0800 Subject: [driver-core PATCH v6 6/9] driver core: Probe devices asynchronously instead of the driver From: Alexander Duyck To: linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org Date: Thu, 08 Nov 2018 10:07:11 -0800 Message-ID: <154170043123.12967.3591757325647337726.stgit@ahduyck-desk1.jf.intel.com> In-Reply-To: <154170028986.12967.2108024712555179678.stgit@ahduyck-desk1.jf.intel.com> References: <154170028986.12967.2108024712555179678.stgit@ahduyck-desk1.jf.intel.com> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-BeenThere: linux-nvdimm@lists.01.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Linux-nvdimm developer list." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: len.brown@intel.com, bvanassche@acm.org, linux-pm@vger.kernel.org, alexander.h.duyck@linux.intel.com, rafael@kernel.org, jiangshanlai@gmail.com, linux-nvdimm@lists.01.org, pavel@ucw.cz, zwisler@kernel.org, tj@kernel.org, akpm@linux-foundation.org Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" X-Virus-Scanned: ClamAV using ClamSMTP Probe devices asynchronously instead of the driver. This results in us seeing the same behavior if the device is registered before the driver or after. This way we can avoid serializing the initialization should the driver not be loaded until after the devices have already been added. The motivation behind this is that if we have a set of devices that take a significant amount of time to load we can greatly reduce the time to load by processing them in parallel instead of one at a time. In addition, each device can exist on a different node so placing a single thread on one CPU to initialize all of the devices for a given driver can result in poor performance on a system with multiple nodes. I am using the driver_data member of the device struct to store the driver pointer while we wait on the deferred probe call. This should be safe to do as the value will either be set to NULL on a failed probe or driver load followed by unload, or the driver value itself will be set on a successful driver load. In addition I have used the async_probe flag to add additional protection as it will be cleared if someone overwrites the driver_data member as a part of loading the driver. Signed-off-by: Alexander Duyck Reviewed-by: Bart Van Assche --- drivers/base/bus.c | 23 ++-------------- drivers/base/dd.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/device.h | 10 ++++++- 3 files changed, 80 insertions(+), 21 deletions(-) diff --git a/drivers/base/bus.c b/drivers/base/bus.c index 8a630f9bd880..0cd2eadd0816 100644 --- a/drivers/base/bus.c +++ b/drivers/base/bus.c @@ -606,17 +606,6 @@ static ssize_t uevent_store(struct device_driver *drv, const char *buf, } static DRIVER_ATTR_WO(uevent); -static void driver_attach_async(void *_drv, async_cookie_t cookie) -{ - struct device_driver *drv = _drv; - int ret; - - ret = driver_attach(drv); - - pr_debug("bus: '%s': driver %s async attach completed: %d\n", - drv->bus->name, drv->name, ret); -} - /** * bus_add_driver - Add a driver to the bus. * @drv: driver. @@ -649,15 +638,9 @@ int bus_add_driver(struct device_driver *drv) klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers); if (drv->bus->p->drivers_autoprobe) { - if (driver_allows_async_probing(drv)) { - pr_debug("bus: '%s': probing driver %s asynchronously\n", - drv->bus->name, drv->name); - async_schedule(driver_attach_async, drv); - } else { - error = driver_attach(drv); - if (error) - goto out_unregister; - } + error = driver_attach(drv); + if (error) + goto out_unregister; } module_add_driver(drv->owner, drv); diff --git a/drivers/base/dd.c b/drivers/base/dd.c index ed19cf0d6f9a..f4e84d639c69 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -808,6 +808,7 @@ static int __device_attach(struct device *dev, bool allow_async) ret = 1; else { dev->driver = NULL; + dev_set_drvdata(dev, NULL); ret = 0; } } else { @@ -925,6 +926,48 @@ int device_driver_attach(struct device_driver *drv, struct device *dev) return ret; } +static inline struct device_driver *dev_get_drv_async(const struct device *dev) +{ + return dev->async_probe ? dev->driver_data : NULL; +} + +static inline void dev_set_drv_async(struct device *dev, + struct device_driver *drv) +{ + /* + * Set async_probe to true indicating we are waiting for this data to be + * loaded as a potential driver. + */ + dev->driver_data = drv; + dev->async_probe = true; +} + +static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie) +{ + struct device *dev = _dev; + struct device_driver *drv; + + __device_driver_lock(dev, dev->parent); + + /* + * If someone attempted to bind a driver either successfully or + * unsuccessfully before we got here we should just skip the driver + * probe call. + */ + drv = dev_get_drv_async(dev); + if (drv && !dev->driver) + driver_probe_device(drv, dev); + + /* We made our attempt at an async_probe, clear the flag */ + dev->async_probe = false; + + __device_driver_unlock(dev, dev->parent); + + put_device(dev); + + dev_dbg(dev, "async probe completed\n"); +} + static int __driver_attach(struct device *dev, void *data) { struct device_driver *drv = data; @@ -952,6 +995,25 @@ static int __driver_attach(struct device *dev, void *data) return ret; } /* ret > 0 means positive match */ + if (driver_allows_async_probing(drv)) { + /* + * Instead of probing the device synchronously we will + * probe it asynchronously to allow for more parallelism. + * + * We only take the device lock here in order to guarantee + * that the dev->driver and driver_data fields are protected + */ + dev_dbg(dev, "scheduling asynchronous probe\n"); + device_lock(dev); + if (!dev->driver) { + get_device(dev); + dev_set_drv_async(dev, drv); + async_schedule(__driver_attach_async_helper, dev); + } + device_unlock(dev); + return 0; + } + device_driver_attach(drv, dev); return 0; @@ -1049,6 +1111,12 @@ void device_release_driver_internal(struct device *dev, { __device_driver_lock(dev, parent); + /* + * We shouldn't need to add a check for any pending async_probe here + * because the only caller that will pass us a driver, driver_detach, + * should have been called after the driver was removed from the bus + * and will call async_synchronize_full before we get to this point. + */ if (!drv || drv == dev->driver) __device_release_driver(dev, parent); diff --git a/include/linux/device.h b/include/linux/device.h index 4d2eb2c74149..2305eb886006 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -910,7 +910,9 @@ struct dev_links_info { * variants, which GPIO pins act in what additional roles, and so * on. This shrinks the "Board Support Packages" (BSPs) and * minimizes board-specific #ifdefs in drivers. - * @driver_data: Private pointer for driver specific info. + * @driver_data: Private pointer for driver specific info if driver is + * non-NULL. Pointer to deferred driver to be attached if driver + * is NULL. * @links: Links to suppliers and consumers of this device. * @power: For device power management. * See Documentation/driver-api/pm/devices.rst for details. @@ -1118,6 +1120,12 @@ static inline void *dev_get_drvdata(const struct device *dev) static inline void dev_set_drvdata(struct device *dev, void *data) { + /* + * clear async_probe to prevent us from attempting to read driver_data + * as a driver. We can reset this to true for the one case where we are + * using this to record an actual driver. + */ + dev->async_probe = false; dev->driver_data = data; }