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Message-ID: <Pine.LNX.4.44L0.0704091029590.3561-100000@iolanthe.rowland.org>
Date: Mon, 9 Apr 2007 10:33:47 -0400 (EDT)
From: Alan Stern <stern@...land.harvard.edu>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Neil Brown <neilb@...e.de>,
Kernel development list <linux-kernel@...r.kernel.org>
Subject: [PATCH] device_schedule_callback needs a module reference
This patch (as896) fixes an oversight in the design of
device_schedule_callback(). It is necessary to acquire a reference to
the module owning the callback routine, to prevent the module from
being unloaded before the callback can run.
Signed-off-by: Alan Stern <stern@...land.harvard.edu>
---
This should remove the need for Neil's
md-avoid-a-deadlock-when-removing-a-device-from-an-md-array-via-sysfs-fix.patch.
The problem is a general one and needs to be fixed for all callers.
Index: usb-2.6/drivers/base/core.c
===================================================================
--- usb-2.6.orig/drivers/base/core.c
+++ usb-2.6/drivers/base/core.c
@@ -431,9 +431,10 @@ void device_remove_bin_file(struct devic
EXPORT_SYMBOL_GPL(device_remove_bin_file);
/**
- * device_schedule_callback - helper to schedule a callback for a device
+ * device_schedule_callback_owner - helper to schedule a callback for a device
* @dev: device.
* @func: callback function to invoke later.
+ * @owner: module owning the callback routine
*
* Attribute methods must not unregister themselves or their parent device
* (which would amount to the same thing). Attempts to do so will deadlock,
@@ -444,20 +445,23 @@ EXPORT_SYMBOL_GPL(device_remove_bin_file
* argument in the workqueue's process context. @dev will be pinned until
* @func returns.
*
+ * This routine is usually called via the inline device_schedule_callback(),
+ * which automatically sets @owner to THIS_MODULE.
+ *
* Returns 0 if the request was submitted, -ENOMEM if storage could not
- * be allocated.
+ * be allocated, -ENODEV if a reference to @owner isn't available.
*
* NOTE: This routine won't work if CONFIG_SYSFS isn't set! It uses an
* underlying sysfs routine (since it is intended for use by attribute
* methods), and if sysfs isn't available you'll get nothing but -ENOSYS.
*/
-int device_schedule_callback(struct device *dev,
- void (*func)(struct device *))
+int device_schedule_callback_owner(struct device *dev,
+ void (*func)(struct device *), struct module *owner)
{
return sysfs_schedule_callback(&dev->kobj,
- (void (*)(void *)) func, dev);
+ (void (*)(void *)) func, dev, owner);
}
-EXPORT_SYMBOL_GPL(device_schedule_callback);
+EXPORT_SYMBOL_GPL(device_schedule_callback_owner);
static void klist_children_get(struct klist_node *n)
{
Index: usb-2.6/fs/sysfs/file.c
===================================================================
--- usb-2.6.orig/fs/sysfs/file.c
+++ usb-2.6/fs/sysfs/file.c
@@ -647,6 +647,7 @@ struct sysfs_schedule_callback_struct {
struct kobject *kobj;
void (*func)(void *);
void *data;
+ struct module *owner;
struct work_struct work;
};
@@ -657,6 +658,7 @@ static void sysfs_schedule_callback_work
(ss->func)(ss->data);
kobject_put(ss->kobj);
+ module_put(ss->owner);
kfree(ss);
}
@@ -665,6 +667,7 @@ static void sysfs_schedule_callback_work
* @kobj: object we're acting for.
* @func: callback function to invoke later.
* @data: argument to pass to @func.
+ * @owner: module owning the callback code
*
* sysfs attribute methods must not unregister themselves or their parent
* kobject (which would amount to the same thing). Attempts to do so will
@@ -677,20 +680,25 @@ static void sysfs_schedule_callback_work
* until @func returns.
*
* Returns 0 if the request was submitted, -ENOMEM if storage could not
- * be allocated.
+ * be allocated, -ENODEV if a reference to @owner isn't available.
*/
int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
- void *data)
+ void *data, struct module *owner)
{
struct sysfs_schedule_callback_struct *ss;
+ if (!try_module_get(owner))
+ return -ENODEV;
ss = kmalloc(sizeof(*ss), GFP_KERNEL);
- if (!ss)
+ if (!ss) {
+ module_put(owner);
return -ENOMEM;
+ }
kobject_get(kobj);
ss->kobj = kobj;
ss->func = func;
ss->data = data;
+ ss->owner = owner;
INIT_WORK(&ss->work, sysfs_schedule_callback_work);
schedule_work(&ss->work);
return 0;
Index: usb-2.6/include/linux/device.h
===================================================================
--- usb-2.6.orig/include/linux/device.h
+++ usb-2.6/include/linux/device.h
@@ -369,8 +369,14 @@ extern int __must_check device_create_bi
struct bin_attribute *attr);
extern void device_remove_bin_file(struct device *dev,
struct bin_attribute *attr);
-extern int device_schedule_callback(struct device *dev,
- void (*func)(struct device *));
+extern int device_schedule_callback_owner(struct device *dev,
+ void (*func)(struct device *), struct module *owner);
+
+static inline int device_schedule_callback(struct device *dev,
+ void (*func)(struct device *))
+{
+ device_schedule_callback_mod(dev, func, THIS_MODULE);
+}
/* device resource management */
typedef void (*dr_release_t)(struct device *dev, void *res);
Index: usb-2.6/include/linux/sysfs.h
===================================================================
--- usb-2.6.orig/include/linux/sysfs.h
+++ usb-2.6/include/linux/sysfs.h
@@ -80,7 +80,7 @@ struct sysfs_ops {
#ifdef CONFIG_SYSFS
extern int sysfs_schedule_callback(struct kobject *kobj,
- void (*func)(void *), void *data);
+ void (*func)(void *), void *data, struct module *owner);
extern int __must_check
sysfs_create_dir(struct kobject *, struct dentry *);
@@ -138,7 +138,7 @@ extern int __must_check sysfs_init(void)
#else /* CONFIG_SYSFS */
static inline int sysfs_schedule_callback(struct kobject *kobj,
- void (*func)(void *), void *data)
+ void (*func)(void *), void *data, struct module *owner)
{
return -ENOSYS;
}
-
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