[PATCH (revised)] device_schedule_callback needs a module reference

[PATCH (revised)] device_schedule_callback needs a module reference

[Alan Stern]

This revised patch (as896b) 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@rowland.harvard.edu>

---

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 *))
+{
+	return device_schedule_callback_owner(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;
 }

Re: [PATCH (revised)] device_schedule_callback needs a module reference

[Cornelia Huck]

On Mon, 9 Apr 2007 11:07:22 -0400 (EDT),
Alan Stern <stern@rowland.harvard.edu> wrote:

> This revised patch (as896b) 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@rowland.harvard.edu>

<snip>

> 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 *))
> +{
> +	return device_schedule_callback_owner(dev, func, THIS_MODULE);
> +}
> 
>  /* device resource management */
>  typedef void (*dr_release_t)(struct device *dev, void *res);

Whoops:

In file included from include/linux/interrupt.h:15,
                 from include/asm/hardirq.h:18,
                 from include/linux/hardirq.h:7,
                 from include/asm-generic/local.h:5,
                 from include/asm/local.h:1,
                 from include/linux/module.h:19,
                 from arch/s390/kernel/time.c:16:
include/linux/device.h: In function 'device_schedule_callback':
include/linux/device.h:374: error: 'THIS_MODULE' undeclared (first use in this function)
include/linux/device.h:374: error: (Each undeclared identifier is reported only once
include/linux/device.h:374: error: for each function it appears in.)

Maybe better move the implementation of device_schedule_callback() to
drivers/base/core.c? (Though I'm not sure why
include/asm-s390/hardirq.h includes linux/interrupt.h, and e.g.
include/asm-i386/hardirq.h doesn't.)

Re: [PATCH (revised)] device_schedule_callback needs a module reference

[Alan Stern]

On Tue, 10 Apr 2007, Cornelia Huck wrote:

> Whoops:
> 
> In file included from include/linux/interrupt.h:15,
>                  from include/asm/hardirq.h:18,
>                  from include/linux/hardirq.h:7,
>                  from include/asm-generic/local.h:5,
>                  from include/asm/local.h:1,
>                  from include/linux/module.h:19,
>                  from arch/s390/kernel/time.c:16:
> include/linux/device.h: In function 'device_schedule_callback':
> include/linux/device.h:374: error: 'THIS_MODULE' undeclared (first use in this function)
> include/linux/device.h:374: error: (Each undeclared identifier is reported only once
> include/linux/device.h:374: error: for each function it appears in.)
> 
> Maybe better move the implementation of device_schedule_callback() to
> drivers/base/core.c? (Though I'm not sure why
> include/asm-s390/hardirq.h includes linux/interrupt.h, and e.g.
> include/asm-i386/hardirq.h doesn't.)

I don't think moving device_schedule_callback() is the answer.  For one 
thing, the implementation _has_ to be compiled in the calling module so 
that THIS_MODULE will have the correct value.  If it were compiled in 
drivers/base/core.c then it wouldn't refer to the caller's module.

The real problem is bad nesting of #includes.  Maybe changing 
include/asm-s390/hardirq.h not to include linux/interrupt.h will be 
feasible.

Or perhaps it would be better to move the definition of THIS_MODULE in
linux/module.h up before all the #include lines, since it seems reasonable
that a file indirectly included by module.h might need to use THIS_MODULE.

Alan Stern

Re: [PATCH (revised)] device_schedule_callback needs a module reference

[Andrew Morton]

On Tue, 10 Apr 2007 12:46:11 -0400 (EDT)
Alan Stern <stern@rowland.harvard.edu> wrote:

> On Tue, 10 Apr 2007, Cornelia Huck wrote:
> 
> > Whoops:
> > 
> > In file included from include/linux/interrupt.h:15,
> >                  from include/asm/hardirq.h:18,
> >                  from include/linux/hardirq.h:7,
> >                  from include/asm-generic/local.h:5,
> >                  from include/asm/local.h:1,
> >                  from include/linux/module.h:19,
> >                  from arch/s390/kernel/time.c:16:
> > include/linux/device.h: In function 'device_schedule_callback':
> > include/linux/device.h:374: error: 'THIS_MODULE' undeclared (first use in this function)
> > include/linux/device.h:374: error: (Each undeclared identifier is reported only once
> > include/linux/device.h:374: error: for each function it appears in.)
> > 
> > Maybe better move the implementation of device_schedule_callback() to
> > drivers/base/core.c? (Though I'm not sure why
> > include/asm-s390/hardirq.h includes linux/interrupt.h, and e.g.
> > include/asm-i386/hardirq.h doesn't.)
> 
> I don't think moving device_schedule_callback() is the answer.  For one 
> thing, the implementation _has_ to be compiled in the calling module so 
> that THIS_MODULE will have the correct value.  If it were compiled in 
> drivers/base/core.c then it wouldn't refer to the caller's module.
> 
> The real problem is bad nesting of #includes.  Maybe changing 
> include/asm-s390/hardirq.h not to include linux/interrupt.h will be 
> feasible.
> 
> Or perhaps it would be better to move the definition of THIS_MODULE in
> linux/module.h up before all the #include lines, since it seems reasonable
> that a file indirectly included by module.h might need to use THIS_MODULE.
> 

<holds nose>


--- a/include/linux/device.h~device_schedule_callback-needs-a-module-reference-fix
+++ a/include/linux/device.h
@@ -369,11 +369,9 @@ extern void device_remove_bin_file(struc
 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 *))
-{
-	return device_schedule_callback_owner(dev, func, THIS_MODULE);
-}
+/* This is a macro to avoid include problems with THIS_MODULE */
+#define device_schedule_callback(dev, func)			\
+	device_schedule_callback_owner(dev, func, THIS_MODULE)
 
 /* device resource management */
 typedef void (*dr_release_t)(struct device *dev, void *res);
_