linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org
Cc: len.brown@intel.com, rafael@kernel.org, linux-pm@vger.kernel.org,
	jiangshanlai@gmail.com, pavel@ucw.cz, zwisler@kernel.org,
	tj@kernel.org, akpm@linux-foundation.org,
	alexander.h.duyck@linux.intel.com
Subject: [driver-core PATCH v4 4/6] driver core: Probe devices asynchronously instead of the driver
Date: Mon, 15 Oct 2018 08:09:26 -0700	[thread overview]
Message-ID: <20181015150926.29520.45280.stgit@localhost.localdomain> (raw)
In-Reply-To: <20181015150305.29520.86363.stgit@localhost.localdomain>

This change makes it so that we 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.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
---
 drivers/base/bus.c     |   23 +++--------------------
 drivers/base/dd.c      |   45 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/device.h |    4 +++-
 3 files changed, 51 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 e845cd2a87af..c33f893ec9d8 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -802,6 +802,7 @@ static int __device_attach(struct device *dev, bool allow_async)
 			ret = 1;
 		else {
 			dev->driver = NULL;
+			dev_set_drvdata(dev, NULL);
 			ret = 0;
 		}
 	} else {
@@ -918,6 +919,31 @@ int device_driver_attach(struct device_driver *drv, struct device *dev)
 	return ret;
 }
 
+static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
+{
+	struct device *dev = _dev;
+
+	__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.
+	 */
+	if (!dev->driver) {
+		struct device_driver *drv = dev_get_drvdata(dev);
+
+		if (drv)
+			driver_probe_device(drv, dev);
+	}
+
+	__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;
@@ -945,6 +971,25 @@ 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_drvdata(dev, drv);
+			async_schedule(__driver_attach_async_helper, dev);
+		}
+		device_unlock(dev);
+		return 0;
+	}
+
 	device_driver_attach(drv, dev);
 
 	return 0;
diff --git a/include/linux/device.h b/include/linux/device.h
index 90224e75ade4..b0abb04c29dc 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -906,7 +906,9 @@ 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.


  parent reply	other threads:[~2018-10-15 15:09 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-15 15:09 [driver-core PATCH v4 0/6] Add NUMA aware async_schedule calls Alexander Duyck
2018-10-15 15:09 ` [driver-core PATCH v4 1/6] workqueue: Provide queue_work_node to queue work near a given NUMA node Alexander Duyck
2018-10-15 15:09 ` [driver-core PATCH v4 2/6] async: Add support for queueing on specific " Alexander Duyck
2018-10-15 15:09 ` [driver-core PATCH v4 3/6] device core: Consolidate locking and unlocking of parent and device Alexander Duyck
2018-10-18  7:46   ` Rafael J. Wysocki
2018-10-18 17:53   ` Bart Van Assche
2018-10-15 15:09 ` Alexander Duyck [this message]
2018-10-18 18:11   ` [driver-core PATCH v4 4/6] driver core: Probe devices asynchronously instead of the driver Bart Van Assche
2018-10-18 19:38     ` Alexander Duyck
2018-10-18 20:13       ` Bart Van Assche
2018-10-19  2:20         ` Alexander Duyck
2018-10-19  2:31           ` Bart Van Assche
2018-10-19 22:35             ` Alexander Duyck
2018-10-15 15:09 ` [driver-core PATCH v4 5/6] driver core: Attach devices on CPU local to device node Alexander Duyck
2018-10-15 15:09 ` [driver-core PATCH v4 6/6] PM core: Use new async_schedule_dev command Alexander Duyck

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181015150926.29520.45280.stgit@localhost.localdomain \
    --to=alexander.h.duyck@linux.intel.com \
    --cc=akpm@linux-foundation.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=jiangshanlai@gmail.com \
    --cc=len.brown@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=pavel@ucw.cz \
    --cc=rafael@kernel.org \
    --cc=tj@kernel.org \
    --cc=zwisler@kernel.org \
    --subject='Re: [driver-core PATCH v4 4/6] driver core: Probe devices asynchronously instead of the driver' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox