9a19fea436
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. 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. 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. 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. 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. 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. 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). 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. 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). Signed-off-by: Patrick Mochel <mochel@digitalimplant.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> diff -Nru a/include/linux/klist.h b/include/linux/klist.h
54 lines
1.2 KiB
C
54 lines
1.2 KiB
C
/*
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* klist.h - Some generic list helpers, extending struct list_head a bit.
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*
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* Implementations are found in lib/klist.c
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*
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*
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* Copyright (C) 2005 Patrick Mochel
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*
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* This file is rleased under the GPL v2.
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*/
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#include <linux/spinlock.h>
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#include <linux/completion.h>
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#include <linux/kref.h>
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#include <linux/list.h>
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struct klist {
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spinlock_t k_lock;
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struct list_head k_list;
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};
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extern void klist_init(struct klist * k);
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struct klist_node {
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struct klist * n_klist;
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struct list_head n_node;
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struct kref n_ref;
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struct completion n_removed;
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};
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extern void klist_add_tail(struct klist * k, struct klist_node * n);
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extern void klist_add_head(struct klist * k, struct klist_node * n);
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extern void klist_del(struct klist_node * n);
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extern void klist_remove(struct klist_node * n);
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struct klist_iter {
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struct klist * i_klist;
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struct list_head * i_head;
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struct klist_node * i_cur;
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};
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extern void klist_iter_init(struct klist * k, struct klist_iter * i);
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extern void klist_iter_init_node(struct klist * k, struct klist_iter * i,
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struct klist_node * n);
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extern void klist_iter_exit(struct klist_iter * i);
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extern struct klist_node * klist_next(struct klist_iter * i);
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