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Commit 53c165e0 authored by James Bottomley's avatar James Bottomley Committed by James Bottomley
Browse files

[SCSI] correct attribute_container list usage 



One of the changes in the attribute_container code in the scsi-misc tree
was to add a lock to protect the list of devices per container.  This,
unfortunately, leads to potential scheduling while atomic problems if
there's a sleep in the function called by a trigger.

The correct solution is to use the kernel klist infrastructure instead
which allows lockless traversal of a list.

Signed-off-by: default avatarJames Bottomley <James.Bottomley@SteelEye.com>
parent 51490c89

drivers/base/attribute_container.c

+29 −22
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ 
/* This is a private structure used to tie the classdev and the

 * container .. it should never be visible outside this file */

struct internal_container {

	struct list_head node;

	struct klist_node node;

	struct attribute_container *cont;

	struct class_device classdev;

};
@@ -57,8 +57,7 @@ int 
attribute_container_register(struct attribute_container *cont)

{

	INIT_LIST_HEAD(&cont->node);

	INIT_LIST_HEAD(&cont->containers);

	spin_lock_init(&cont->containers_lock);

	klist_init(&cont->containers);

		

	down(&attribute_container_mutex);

	list_add_tail(&cont->node, &attribute_container_list);
@@ -78,13 +77,13 @@ attribute_container_unregister(struct attribute_container *cont) 
{

	int retval = -EBUSY;

	down(&attribute_container_mutex);

	spin_lock(&cont->containers_lock);

	if (!list_empty(&cont->containers))

	spin_lock(&cont->containers.k_lock);

	if (!list_empty(&cont->containers.k_list))

		goto out;

	retval = 0;

	list_del(&cont->node);

 out:

	spin_unlock(&cont->containers_lock);

	spin_unlock(&cont->containers.k_lock);

	up(&attribute_container_mutex);

	return retval;
@@ -143,7 +142,6 @@ attribute_container_add_device(struct device *dev, 
			continue;

		}

		memset(ic, 0, sizeof(struct internal_container));

		INIT_LIST_HEAD(&ic->node);

		ic->cont = cont;

		class_device_initialize(&ic->classdev);

		ic->classdev.dev = get_device(dev);
@@ -154,13 +152,22 @@ attribute_container_add_device(struct device *dev, 
			fn(cont, dev, &ic->classdev);

		else

			attribute_container_add_class_device(&ic->classdev);

		spin_lock(&cont->containers_lock);

		list_add_tail(&ic->node, &cont->containers);

		spin_unlock(&cont->containers_lock);

		klist_add_tail(&ic->node, &cont->containers);

	}

	up(&attribute_container_mutex);

}



/* FIXME: can't break out of this unless klist_iter_exit is also

 * called before doing the break

 */

#define klist_for_each_entry(pos, head, member, iter) \

	for (klist_iter_init(head, iter); (pos = ({ \

		struct klist_node *n = klist_next(iter); \

		n ? ({ klist_iter_exit(iter) ; NULL; }) : \

			container_of(n, typeof(*pos), member);\

	}) ) != NULL; )

			



/**

 * attribute_container_remove_device - make device eligible for removal.

 *
@@ -187,18 +194,19 @@ attribute_container_remove_device(struct device *dev, 


	down(&attribute_container_mutex);

	list_for_each_entry(cont, &attribute_container_list, node) {

		struct internal_container *ic, *tmp;

		struct internal_container *ic;

		struct klist_iter iter;



		if (attribute_container_no_classdevs(cont))

			continue;



		if (!cont->match(cont, dev))

			continue;

		spin_lock(&cont->containers_lock);

		list_for_each_entry_safe(ic, tmp, &cont->containers, node) {



		klist_for_each_entry(ic, &cont->containers, node, &iter) {

			if (dev != ic->classdev.dev)

				continue;

			list_del(&ic->node);

			klist_remove(&ic->node);

			if (fn)

				fn(cont, dev, &ic->classdev);

			else {
@@ -206,7 +214,6 @@ attribute_container_remove_device(struct device *dev, 
				class_device_unregister(&ic->classdev);

			}

		}

		spin_unlock(&cont->containers_lock);

	}

	up(&attribute_container_mutex);

}
@@ -232,7 +239,8 @@ attribute_container_device_trigger(struct device *dev, 


	down(&attribute_container_mutex);

	list_for_each_entry(cont, &attribute_container_list, node) {

		struct internal_container *ic, *tmp;

		struct internal_container *ic;

		struct klist_iter iter;



		if (!cont->match(cont, dev))

			continue;
@@ -242,12 +250,10 @@ attribute_container_device_trigger(struct device *dev, 
			continue;

		}



		spin_lock(&cont->containers_lock);

		list_for_each_entry_safe(ic, tmp, &cont->containers, node) {

		klist_for_each_entry(ic, &cont->containers, node, &iter) {

			if (dev == ic->classdev.dev)

				fn(cont, dev, &ic->classdev);

		}

		spin_unlock(&cont->containers_lock);

	}

	up(&attribute_container_mutex);

}
@@ -397,15 +403,16 @@ attribute_container_find_class_device(struct attribute_container *cont, 
{

	struct class_device *cdev = NULL;

	struct internal_container *ic;

	struct klist_iter iter;



	spin_lock(&cont->containers_lock);

	list_for_each_entry(ic, &cont->containers, node) {

	klist_for_each_entry(ic, &cont->containers, node, &iter) {

		if (ic->classdev.dev == dev) {

			cdev = &ic->classdev;

			/* FIXME: must exit iterator then break */

			klist_iter_exit(&iter);

			break;

		}

	}

	spin_unlock(&cont->containers_lock);



	return cdev;

}

include/linux/attribute_container.h

+2 −2
Original line number Diff line number Diff line
@@ -11,12 +11,12 @@ 


#include <linux/device.h>

#include <linux/list.h>

#include <linux/klist.h>

#include <linux/spinlock.h>



struct attribute_container {

	struct list_head	node;

	struct list_head	containers;

	spinlock_t		containers_lock;

	struct klist		containers;

	struct class		*class;

	struct class_device_attribute **attrs;

	int (*match)(struct attribute_container *, struct device *);