debuggers.hg

view xen/common/notifier.c @ 22848:6341fe0f4e5a

Added tag 4.1.0-rc2 for changeset 9dca60d88c63
author Keir Fraser <keir@xen.org>
date Tue Jan 25 14:06:55 2011 +0000 (2011-01-25)
parents 1b49bfd3b0d7
children
line source
1 /******************************************************************************
2 * common/notifier.c
3 *
4 * Routines to manage notifier chains for passing status changes to any
5 * interested routines.
6 *
7 * Original code from Linux kernel 2.6.27 (Alan Cox <Alan.Cox@linux.org>)
8 */
10 #include <xen/config.h>
11 #include <xen/init.h>
12 #include <xen/notifier.h>
14 /**
15 * notifier_chain_register - Add notifier to a raw notifier chain
16 * @nh: Pointer to head of the raw notifier chain
17 * @n: New entry in notifier chain
18 *
19 * Adds a notifier to a raw notifier chain.
20 * All locking must be provided by the caller.
21 */
22 void notifier_chain_register(
23 struct notifier_head *nh, struct notifier_block *n)
24 {
25 struct list_head *chain = &nh->head.chain;
26 struct notifier_block *nb;
28 while ( chain->next != &nh->head.chain )
29 {
30 nb = list_entry(chain->next, struct notifier_block, chain);
31 if ( n->priority > nb->priority )
32 break;
33 chain = chain->next;
34 }
36 list_add(&n->chain, chain);
37 }
39 /**
40 * notifier_chain_unregister - Remove notifier from a raw notifier chain
41 * @nh: Pointer to head of the raw notifier chain
42 * @n: Entry to remove from notifier chain
43 *
44 * Removes a notifier from a raw notifier chain.
45 * All locking must be provided by the caller.
46 */
47 void notifier_chain_unregister(
48 struct notifier_head *nh, struct notifier_block *n)
49 {
50 list_del(&n->chain);
51 }
53 /**
54 * notifier_call_chain - Informs the registered notifiers about an event.
55 * @nh: Pointer to head of the raw notifier chain
56 * @val: Value passed unmodified to notifier function
57 * @v: Pointer passed unmodified to notifier function
58 * @pcursor: If non-NULL, position in chain to start from. Also updated on
59 * return to indicate how far notifications got before stopping.
60 *
61 * Calls each function in a notifier chain in turn. The functions run in an
62 * undefined context. All locking must be provided by the caller.
63 *
64 * If the return value of the notifier can be and'ed with %NOTIFY_STOP_MASK
65 * then notifier_call_chain() will return immediately, with teh return value of
66 * the notifier function which halted execution. Otherwise the return value is
67 * the return value of the last notifier function called.
68 */
69 int notifier_call_chain(
70 struct notifier_head *nh, unsigned long val, void *v,
71 struct notifier_block **pcursor)
72 {
73 int ret = NOTIFY_DONE;
74 struct list_head *cursor;
75 struct notifier_block *nb;
76 bool_t reverse = !!(val & NOTIFY_REVERSE);
78 cursor = &(pcursor && *pcursor ? *pcursor : &nh->head)->chain;
80 do {
81 cursor = reverse ? cursor->prev : cursor->next;
82 nb = list_entry(cursor, struct notifier_block, chain);
83 if ( cursor == &nh->head.chain )
84 break;
85 ret = nb->notifier_call(nb, val, v);
86 } while ( !(ret & NOTIFY_STOP_MASK) );
88 if ( pcursor )
89 *pcursor = nb;
91 return ret;
92 }