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notifier_list_notify() has no return value. This is fine when we just want to invoke side-effects. Sometimes it's useful for notifiers to produce a return value. This allows notifiers to "veto" an operation and will be used by the block layer before-write notifier. Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
73 lines
1.8 KiB
C
73 lines
1.8 KiB
C
/*
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* Notifier lists
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*
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* Copyright IBM, Corp. 2010
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#ifndef QEMU_NOTIFY_H
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#define QEMU_NOTIFY_H
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#include "qemu/queue.h"
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typedef struct Notifier Notifier;
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struct Notifier
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{
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void (*notify)(Notifier *notifier, void *data);
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QLIST_ENTRY(Notifier) node;
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};
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typedef struct NotifierList
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{
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QLIST_HEAD(, Notifier) notifiers;
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} NotifierList;
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#define NOTIFIER_LIST_INITIALIZER(head) \
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{ QLIST_HEAD_INITIALIZER((head).notifiers) }
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void notifier_list_init(NotifierList *list);
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void notifier_list_add(NotifierList *list, Notifier *notifier);
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void notifier_remove(Notifier *notifier);
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void notifier_list_notify(NotifierList *list, void *data);
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/* Same as Notifier but allows .notify() to return errors */
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typedef struct NotifierWithReturn NotifierWithReturn;
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struct NotifierWithReturn {
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/**
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* Return 0 on success (next notifier will be invoked), otherwise
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* notifier_with_return_list_notify() will stop and return the value.
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*/
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int (*notify)(NotifierWithReturn *notifier, void *data);
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QLIST_ENTRY(NotifierWithReturn) node;
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};
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typedef struct NotifierWithReturnList {
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QLIST_HEAD(, NotifierWithReturn) notifiers;
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} NotifierWithReturnList;
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#define NOTIFIER_WITH_RETURN_LIST_INITIALIZER(head) \
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{ QLIST_HEAD_INITIALIZER((head).notifiers) }
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void notifier_with_return_list_init(NotifierWithReturnList *list);
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void notifier_with_return_list_add(NotifierWithReturnList *list,
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NotifierWithReturn *notifier);
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void notifier_with_return_remove(NotifierWithReturn *notifier);
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int notifier_with_return_list_notify(NotifierWithReturnList *list,
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void *data);
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#endif
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