X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=lib%2Fklist.c;h=573d6068a42e4377dcb26851175423d1864957ff;hb=bca516bfcfeb545e00bad3b6ca075d91c9c0b365;hp=738ab810160a85b1c437da82e0389d354c76cf20;hpb=0293a509405dccecc30783a5d729d615b68d6a77;p=safe%2Fjmp%2Flinux-2.6 diff --git a/lib/klist.c b/lib/klist.c index 738ab81..573d606 100644 --- a/lib/klist.c +++ b/lib/klist.c @@ -1,265 +1,365 @@ /* - * klist.c - Routines for manipulating klists. + * klist.c - Routines for manipulating klists. * + * Copyright (C) 2005 Patrick Mochel * - * This klist interface provides a couple of structures that wrap around - * struct list_head to provide explicit list "head" (struct klist) and - * list "node" (struct klist_node) objects. For struct klist, a spinlock - * is included that protects access to the actual list itself. struct - * klist_node provides a pointer to the klist that owns it and a kref - * reference count that indicates the number of current users of that node - * in the list. + * This file is released under the GPL v2. * - * The entire point is to provide an interface for iterating over a list - * that is safe and allows for modification of the list during the - * iteration (e.g. insertion and removal), including modification of the - * current node on the list. + * This klist interface provides a couple of structures that wrap around + * struct list_head to provide explicit list "head" (struct klist) and list + * "node" (struct klist_node) objects. For struct klist, a spinlock is + * included that protects access to the actual list itself. struct + * klist_node provides a pointer to the klist that owns it and a kref + * reference count that indicates the number of current users of that node + * in the list. * - * It works using a 3rd object type - struct klist_iter - that is declared - * and initialized before an iteration. klist_next() is used to acquire the - * next element in the list. It returns NULL if there are no more items. - * Internally, that routine takes the klist's lock, decrements the reference - * count of the previous klist_node and increments the count of the next - * klist_node. It then drops the lock and returns. + * The entire point is to provide an interface for iterating over a list + * that is safe and allows for modification of the list during the + * iteration (e.g. insertion and removal), including modification of the + * current node on the list. * - * There are primitives for adding and removing nodes to/from a klist. - * When deleting, klist_del() will simply decrement the reference count. - * Only when the count goes to 0 is the node removed from the list. - * klist_remove() will try to delete the node from the list and block - * until it is actually removed. This is useful for objects (like devices) - * that have been removed from the system and must be freed (but must wait - * until all accessors have finished). + * It works using a 3rd object type - struct klist_iter - that is declared + * and initialized before an iteration. klist_next() is used to acquire the + * next element in the list. It returns NULL if there are no more items. + * Internally, that routine takes the klist's lock, decrements the + * reference count of the previous klist_node and increments the count of + * the next klist_node. It then drops the lock and returns. * - * Copyright (C) 2005 Patrick Mochel - * - * This file is released under the GPL v2. + * There are primitives for adding and removing nodes to/from a klist. + * When deleting, klist_del() will simply decrement the reference count. + * Only when the count goes to 0 is the node removed from the list. + * klist_remove() will try to delete the node from the list and block until + * it is actually removed. This is useful for objects (like devices) that + * have been removed from the system and must be freed (but must wait until + * all accessors have finished). */ #include #include +#include + +/* + * Use the lowest bit of n_klist to mark deleted nodes and exclude + * dead ones from iteration. + */ +#define KNODE_DEAD 1LU +#define KNODE_KLIST_MASK ~KNODE_DEAD +static struct klist *knode_klist(struct klist_node *knode) +{ + return (struct klist *) + ((unsigned long)knode->n_klist & KNODE_KLIST_MASK); +} + +static bool knode_dead(struct klist_node *knode) +{ + return (unsigned long)knode->n_klist & KNODE_DEAD; +} + +static void knode_set_klist(struct klist_node *knode, struct klist *klist) +{ + knode->n_klist = klist; + /* no knode deserves to start its life dead */ + WARN_ON(knode_dead(knode)); +} + +static void knode_kill(struct klist_node *knode) +{ + /* and no knode should die twice ever either, see we're very humane */ + WARN_ON(knode_dead(knode)); + *(unsigned long *)&knode->n_klist |= KNODE_DEAD; +} /** - * klist_init - Initialize a klist structure. - * @k: The klist we're initializing. + * klist_init - Initialize a klist structure. + * @k: The klist we're initializing. + * @get: The get function for the embedding object (NULL if none) + * @put: The put function for the embedding object (NULL if none) + * + * Initialises the klist structure. If the klist_node structures are + * going to be embedded in refcounted objects (necessary for safe + * deletion) then the get/put arguments are used to initialise + * functions that take and release references on the embedding + * objects. */ - -void klist_init(struct klist * k) +void klist_init(struct klist *k, void (*get)(struct klist_node *), + void (*put)(struct klist_node *)) { INIT_LIST_HEAD(&k->k_list); spin_lock_init(&k->k_lock); + k->get = get; + k->put = put; } - EXPORT_SYMBOL_GPL(klist_init); - -static void add_head(struct klist * k, struct klist_node * n) +static void add_head(struct klist *k, struct klist_node *n) { spin_lock(&k->k_lock); list_add(&n->n_node, &k->k_list); spin_unlock(&k->k_lock); } -static void add_tail(struct klist * k, struct klist_node * n) +static void add_tail(struct klist *k, struct klist_node *n) { spin_lock(&k->k_lock); list_add_tail(&n->n_node, &k->k_list); spin_unlock(&k->k_lock); } - -static void klist_node_init(struct klist * k, struct klist_node * n) +static void klist_node_init(struct klist *k, struct klist_node *n) { INIT_LIST_HEAD(&n->n_node); - init_completion(&n->n_removed); kref_init(&n->n_ref); - n->n_klist = k; + knode_set_klist(n, k); + if (k->get) + k->get(n); } - /** - * klist_add_head - Initialize a klist_node and add it to front. - * @k: klist it's going on. - * @n: node we're adding. + * klist_add_head - Initialize a klist_node and add it to front. + * @n: node we're adding. + * @k: klist it's going on. */ - -void klist_add_head(struct klist * k, struct klist_node * n) +void klist_add_head(struct klist_node *n, struct klist *k) { klist_node_init(k, n); add_head(k, n); } - EXPORT_SYMBOL_GPL(klist_add_head); +/** + * klist_add_tail - Initialize a klist_node and add it to back. + * @n: node we're adding. + * @k: klist it's going on. + */ +void klist_add_tail(struct klist_node *n, struct klist *k) +{ + klist_node_init(k, n); + add_tail(k, n); +} +EXPORT_SYMBOL_GPL(klist_add_tail); /** - * klist_add_tail - Initialize a klist_node and add it to back. - * @k: klist it's going on. - * @n: node we're adding. + * klist_add_after - Init a klist_node and add it after an existing node + * @n: node we're adding. + * @pos: node to put @n after */ +void klist_add_after(struct klist_node *n, struct klist_node *pos) +{ + struct klist *k = knode_klist(pos); -void klist_add_tail(struct klist * k, struct klist_node * n) + klist_node_init(k, n); + spin_lock(&k->k_lock); + list_add(&n->n_node, &pos->n_node); + spin_unlock(&k->k_lock); +} +EXPORT_SYMBOL_GPL(klist_add_after); + +/** + * klist_add_before - Init a klist_node and add it before an existing node + * @n: node we're adding. + * @pos: node to put @n after + */ +void klist_add_before(struct klist_node *n, struct klist_node *pos) { + struct klist *k = knode_klist(pos); + klist_node_init(k, n); - add_tail(k, n); + spin_lock(&k->k_lock); + list_add_tail(&n->n_node, &pos->n_node); + spin_unlock(&k->k_lock); } +EXPORT_SYMBOL_GPL(klist_add_before); -EXPORT_SYMBOL_GPL(klist_add_tail); +struct klist_waiter { + struct list_head list; + struct klist_node *node; + struct task_struct *process; + int woken; +}; +static DEFINE_SPINLOCK(klist_remove_lock); +static LIST_HEAD(klist_remove_waiters); -static void klist_release(struct kref * kref) +static void klist_release(struct kref *kref) { - struct klist_node * n = container_of(kref, struct klist_node, n_ref); + struct klist_waiter *waiter, *tmp; + struct klist_node *n = container_of(kref, struct klist_node, n_ref); + + WARN_ON(!knode_dead(n)); list_del(&n->n_node); - complete(&n->n_removed); - n->n_klist = NULL; + spin_lock(&klist_remove_lock); + list_for_each_entry_safe(waiter, tmp, &klist_remove_waiters, list) { + if (waiter->node != n) + continue; + + waiter->woken = 1; + mb(); + wake_up_process(waiter->process); + list_del(&waiter->list); + } + spin_unlock(&klist_remove_lock); + knode_set_klist(n, NULL); } -static int klist_dec_and_del(struct klist_node * n) +static int klist_dec_and_del(struct klist_node *n) { return kref_put(&n->n_ref, klist_release); } - -/** - * klist_del - Decrement the reference count of node and try to remove. - * @n: node we're deleting. - */ - -void klist_del(struct klist_node * n) +static void klist_put(struct klist_node *n, bool kill) { - struct klist * k = n->n_klist; + struct klist *k = knode_klist(n); + void (*put)(struct klist_node *) = k->put; spin_lock(&k->k_lock); - klist_dec_and_del(n); + if (kill) + knode_kill(n); + if (!klist_dec_and_del(n)) + put = NULL; spin_unlock(&k->k_lock); + if (put) + put(n); } +/** + * klist_del - Decrement the reference count of node and try to remove. + * @n: node we're deleting. + */ +void klist_del(struct klist_node *n) +{ + klist_put(n, true); +} EXPORT_SYMBOL_GPL(klist_del); - /** - * klist_remove - Decrement the refcount of node and wait for it to go away. - * @n: node we're removing. + * klist_remove - Decrement the refcount of node and wait for it to go away. + * @n: node we're removing. */ - -void klist_remove(struct klist_node * n) +void klist_remove(struct klist_node *n) { - struct klist * k = n->n_klist; - spin_lock(&k->k_lock); - klist_dec_and_del(n); - spin_unlock(&k->k_lock); - wait_for_completion(&n->n_removed); + struct klist_waiter waiter; + + waiter.node = n; + waiter.process = current; + waiter.woken = 0; + spin_lock(&klist_remove_lock); + list_add(&waiter.list, &klist_remove_waiters); + spin_unlock(&klist_remove_lock); + + klist_del(n); + + for (;;) { + set_current_state(TASK_UNINTERRUPTIBLE); + if (waiter.woken) + break; + schedule(); + } + __set_current_state(TASK_RUNNING); } - EXPORT_SYMBOL_GPL(klist_remove); - /** - * klist_node_attached - Say whether a node is bound to a list or not. - * @n: Node that we're testing. + * klist_node_attached - Say whether a node is bound to a list or not. + * @n: Node that we're testing. */ - -int klist_node_attached(struct klist_node * n) +int klist_node_attached(struct klist_node *n) { return (n->n_klist != NULL); } - EXPORT_SYMBOL_GPL(klist_node_attached); - /** - * klist_iter_init_node - Initialize a klist_iter structure. - * @k: klist we're iterating. - * @i: klist_iter we're filling. - * @n: node to start with. + * klist_iter_init_node - Initialize a klist_iter structure. + * @k: klist we're iterating. + * @i: klist_iter we're filling. + * @n: node to start with. * - * Similar to klist_iter_init(), but starts the action off with @n, - * instead of with the list head. + * Similar to klist_iter_init(), but starts the action off with @n, + * instead of with the list head. */ - -void klist_iter_init_node(struct klist * k, struct klist_iter * i, struct klist_node * n) +void klist_iter_init_node(struct klist *k, struct klist_iter *i, + struct klist_node *n) { i->i_klist = k; - i->i_head = &k->k_list; i->i_cur = n; + if (n) + kref_get(&n->n_ref); } - EXPORT_SYMBOL_GPL(klist_iter_init_node); - /** - * klist_iter_init - Iniitalize a klist_iter structure. - * @k: klist we're iterating. - * @i: klist_iter structure we're filling. + * klist_iter_init - Iniitalize a klist_iter structure. + * @k: klist we're iterating. + * @i: klist_iter structure we're filling. * - * Similar to klist_iter_init_node(), but start with the list head. + * Similar to klist_iter_init_node(), but start with the list head. */ - -void klist_iter_init(struct klist * k, struct klist_iter * i) +void klist_iter_init(struct klist *k, struct klist_iter *i) { klist_iter_init_node(k, i, NULL); } - EXPORT_SYMBOL_GPL(klist_iter_init); - /** - * klist_iter_exit - Finish a list iteration. - * @i: Iterator structure. + * klist_iter_exit - Finish a list iteration. + * @i: Iterator structure. * - * Must be called when done iterating over list, as it decrements the - * refcount of the current node. Necessary in case iteration exited before - * the end of the list was reached, and always good form. + * Must be called when done iterating over list, as it decrements the + * refcount of the current node. Necessary in case iteration exited before + * the end of the list was reached, and always good form. */ - -void klist_iter_exit(struct klist_iter * i) +void klist_iter_exit(struct klist_iter *i) { if (i->i_cur) { - klist_del(i->i_cur); + klist_put(i->i_cur, false); i->i_cur = NULL; } } - EXPORT_SYMBOL_GPL(klist_iter_exit); - -static struct klist_node * to_klist_node(struct list_head * n) +static struct klist_node *to_klist_node(struct list_head *n) { return container_of(n, struct klist_node, n_node); } - /** - * klist_next - Ante up next node in list. - * @i: Iterator structure. + * klist_next - Ante up next node in list. + * @i: Iterator structure. * - * First grab list lock. Decrement the reference count of the previous - * node, if there was one. Grab the next node, increment its reference - * count, drop the lock, and return that next node. + * First grab list lock. Decrement the reference count of the previous + * node, if there was one. Grab the next node, increment its reference + * count, drop the lock, and return that next node. */ - -struct klist_node * klist_next(struct klist_iter * i) +struct klist_node *klist_next(struct klist_iter *i) { - struct list_head * next; - struct klist_node * knode = NULL; + void (*put)(struct klist_node *) = i->i_klist->put; + struct klist_node *last = i->i_cur; + struct klist_node *next; spin_lock(&i->i_klist->k_lock); - if (i->i_cur) { - next = i->i_cur->n_node.next; - klist_dec_and_del(i->i_cur); - } else - next = i->i_head->next; - if (next != i->i_head) { - knode = to_klist_node(next); - kref_get(&knode->n_ref); + if (last) { + next = to_klist_node(last->n_node.next); + if (!klist_dec_and_del(last)) + put = NULL; + } else + next = to_klist_node(i->i_klist->k_list.next); + + i->i_cur = NULL; + while (next != to_klist_node(&i->i_klist->k_list)) { + if (likely(!knode_dead(next))) { + kref_get(&next->n_ref); + i->i_cur = next; + break; + } + next = to_klist_node(next->n_node.next); } - i->i_cur = knode; + spin_unlock(&i->i_klist->k_lock); - return knode; -} + if (put && last) + put(last); + return i->i_cur; +} EXPORT_SYMBOL_GPL(klist_next); - -