Revert "driver core: Fix uevent_show() vs driver detach race"

This reverts commit 15fffc6.

This commit causes a regression, so revert it for now until it can come
back in a way that works for everyone.

Link: https://lore.kernel.org/all/172790598832.1168608.4519484276671503678.stgit@dwillia2-xfh.jf.intel.com/
Fixes: 15fffc6 ("driver core: Fix uevent_show() vs driver detach race")
Cc: stable <stable@kernel.org>
Cc: Ashish Sangwan <a.sangwan@samsung.com>
Cc: Namjae Jeon <namjae.jeon@samsung.com>
Cc: Dirk Behme <dirk.behme@de.bosch.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/core.c

@@ -26,7 +26,6 @@
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/pm_runtime.h>
-#include <linux/rcupdate.h>
 #include <linux/sched/mm.h>
 #include <linux/sched/signal.h>
 #include <linux/slab.h>
@@ -2634,7 +2633,6 @@ static const char *dev_uevent_name(const struct kobject *kobj)
 static int dev_uevent(const struct kobject *kobj, struct kobj_uevent_env *env)
 {
 	const struct device *dev = kobj_to_dev(kobj);
-	struct device_driver *driver;
 	int retval = 0;
 
 	/* add device node properties if present */
@@ -2663,12 +2661,8 @@ static int dev_uevent(const struct kobject *kobj, struct kobj_uevent_env *env)
 	if (dev->type && dev->type->name)
 		add_uevent_var(env, "DEVTYPE=%s", dev->type->name);
 
-	/* Synchronize with module_remove_driver() */
-	rcu_read_lock();
-	driver = READ_ONCE(dev->driver);
-	if (driver)
-		add_uevent_var(env, "DRIVER=%s", driver->name);
-	rcu_read_unlock();
+	if (dev->driver)
+		add_uevent_var(env, "DRIVER=%s", dev->driver->name);
 
 	/* Add common DT information about the device */
 	of_device_uevent(dev, env);
@@ -2738,8 +2732,11 @@ static ssize_t uevent_show(struct device *dev, struct device_attribute *attr,
 	if (!env)
 		return -ENOMEM;
 
+	/* Synchronize with really_probe() */
+	device_lock(dev);
 	/* let the kset specific function add its keys */
 	retval = kset->uevent_ops->uevent(&dev->kobj, env);
+	device_unlock(dev);
 	if (retval)
 		goto out;
 

drivers/base/module.c

@@ -7,7 +7,6 @@
 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/string.h>
-#include <linux/rcupdate.h>
 #include "base.h"
 
 static char *make_driver_name(const struct device_driver *drv)
@@ -102,9 +101,6 @@ void module_remove_driver(const struct device_driver *drv)
 	if (!drv)
 		return;
 
-	/* Synchronize with dev_uevent() */
-	synchronize_rcu();
-
 	sysfs_remove_link(&drv->p->kobj, "module");
 
 	if (drv->owner)