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. While implementing this patch, some bugs were found in klist, so the attached patch depends on this patch: http://marc.theaimsgroup.com/?l=linux-kernel&m=112445733108094 James diff --git a/drivers/base/attribute_container.c b/drivers/base/attribute_container.c --- a/drivers/base/attribute_container.c +++ b/drivers/base/attribute_container.c @@ -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 at { 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 de 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 de 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 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 class_device_unregister(&ic->classdev); } } - spin_unlock(&cont->containers_lock); } up(&attribute_container_mutex); } @@ -232,7 +239,8 @@ attribute_container_device_trigger(struc 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(struc 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(st { 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; } diff --git a/include/linux/attribute_container.h b/include/linux/attribute_container.h --- a/include/linux/attribute_container.h +++ b/include/linux/attribute_container.h @@ -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 *); - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
