linux-kernel - [PATCH] driver core: remove polling for driver_probe

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Message-Id: <1233319715-4877-1-git-send-email-tom.leiming@gmail.com>
Date:	Fri, 30 Jan 2009 20:48:35 +0800
From:	tom.leiming@...il.com
To:	kay.sievers@...y.org, greg@...ah.com
Cc:	cornelia.huck@...ibm.com, arjan@...radead.org,
	linux-kernel@...r.kernel.org, Ming Lei <tom.leiming@...il.com>
Subject: [PATCH] driver core: remove polling for driver_probe_done(v3)

From: Ming Lei <tom.leiming@...il.com>

This patch adds a function : driver_wait_probe_done,
which waits on condition of probing done to replace
polling for driver_probe_done in fs initialization.

There is no better way to avoid polling for
driver_probe_done _and_ existence of the root device,
so we does not replace the driver_probe_done with
driver_wait_probe_done in such special case.

Removing polling in fs initialization may lead to
a faster boot.

Signed-off-by: Ming Lei <tom.leiming@...il.com>
---
 drivers/base/dd.c      |   12 ++++++++++++
 include/linux/device.h |    1 +
 init/do_mounts.c       |    4 ++--
 init/do_mounts_md.c    |    3 +--
 4 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 9b721d3..8f9f6fb 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -168,6 +168,18 @@ int driver_probe_done(void)
 }
 
 /**
+ * driver_wait_probe_done
+ * Wait until the probe sequence is finished.
+ *
+ */
+void driver_wait_probe_done(void)
+{
+	pr_debug("%s: probe_count = %d\n", __func__,
+		 atomic_read(&probe_count));
+	wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
+}
+
+/**
  * driver_probe_device - attempt to bind device & driver together
  * @drv: driver to bind a device to
  * @dev: device to try to bind to the driver
diff --git a/include/linux/device.h b/include/linux/device.h
index 45e5b19..c53cdbf 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -147,6 +147,7 @@ extern void put_driver(struct device_driver *drv);
 extern struct device_driver *driver_find(const char *name,
 					 struct bus_type *bus);
 extern int driver_probe_done(void);
+extern void driver_wait_probe_done(void);
 
 /* sysfs interface for exporting driver attributes */
 
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 708105e..9cb1985 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -371,8 +371,8 @@ void __init prepare_namespace(void)
 	}
 
 	/* wait for the known devices to complete their probing */
-	while (driver_probe_done() != 0)
-		msleep(100);
+	driver_wait_probe_done();
+
 	async_synchronize_full();
 
 	md_run_setup();
diff --git a/init/do_mounts_md.c b/init/do_mounts_md.c
index ff95e31..63b77f0 100644
--- a/init/do_mounts_md.c
+++ b/init/do_mounts_md.c
@@ -281,8 +281,7 @@ static void __init autodetect_raid(void)
 	 */
 	printk(KERN_INFO "md: Waiting for all devices to be available before autodetect\n");
 	printk(KERN_INFO "md: If you don't use raid, use raid=noautodetect\n");
-	while (driver_probe_done() < 0)
-		msleep(100);
+	driver_wait_probe_done();
 	fd = sys_open("/dev/md0", 0, 0);
 	if (fd >= 0) {
 		sys_ioctl(fd, RAID_AUTORUN, raid_autopart);
-- 
1.6.0

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