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author | Stefan Hajnoczi <stefanha@redhat.com> | 2013-06-24 17:13:09 +0200 |
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committer | Kevin Wolf <kwolf@redhat.com> | 2013-06-28 09:20:26 +0200 |
commit | 5dae8e5fb803f53fadc116cefe353953b938cbe1 (patch) | |
tree | 65f12d6da71012da6e771a0c2d6c4bb0c9df7d43 | |
parent | a5c5ea3f60c000bf18c99435439533728a5f34a2 (diff) | |
download | hqemu-5dae8e5fb803f53fadc116cefe353953b938cbe1.zip hqemu-5dae8e5fb803f53fadc116cefe353953b938cbe1.tar.gz |
notify: add NotiferWithReturn so notifier list can abort
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>
-rw-r--r-- | include/qemu/notify.h | 29 | ||||
-rw-r--r-- | util/notify.c | 30 |
2 files changed, 59 insertions, 0 deletions
diff --git a/include/qemu/notify.h b/include/qemu/notify.h index 4e2e7f0..a3d73e4 100644 --- a/include/qemu/notify.h +++ b/include/qemu/notify.h @@ -40,4 +40,33 @@ void notifier_remove(Notifier *notifier); void notifier_list_notify(NotifierList *list, void *data); +/* Same as Notifier but allows .notify() to return errors */ +typedef struct NotifierWithReturn NotifierWithReturn; + +struct NotifierWithReturn { + /** + * Return 0 on success (next notifier will be invoked), otherwise + * notifier_with_return_list_notify() will stop and return the value. + */ + int (*notify)(NotifierWithReturn *notifier, void *data); + QLIST_ENTRY(NotifierWithReturn) node; +}; + +typedef struct NotifierWithReturnList { + QLIST_HEAD(, NotifierWithReturn) notifiers; +} NotifierWithReturnList; + +#define NOTIFIER_WITH_RETURN_LIST_INITIALIZER(head) \ + { QLIST_HEAD_INITIALIZER((head).notifiers) } + +void notifier_with_return_list_init(NotifierWithReturnList *list); + +void notifier_with_return_list_add(NotifierWithReturnList *list, + NotifierWithReturn *notifier); + +void notifier_with_return_remove(NotifierWithReturn *notifier); + +int notifier_with_return_list_notify(NotifierWithReturnList *list, + void *data); + #endif diff --git a/util/notify.c b/util/notify.c index 7b7692a..f215dfc 100644 --- a/util/notify.c +++ b/util/notify.c @@ -39,3 +39,33 @@ void notifier_list_notify(NotifierList *list, void *data) notifier->notify(notifier, data); } } + +void notifier_with_return_list_init(NotifierWithReturnList *list) +{ + QLIST_INIT(&list->notifiers); +} + +void notifier_with_return_list_add(NotifierWithReturnList *list, + NotifierWithReturn *notifier) +{ + QLIST_INSERT_HEAD(&list->notifiers, notifier, node); +} + +void notifier_with_return_remove(NotifierWithReturn *notifier) +{ + QLIST_REMOVE(notifier, node); +} + +int notifier_with_return_list_notify(NotifierWithReturnList *list, void *data) +{ + NotifierWithReturn *notifier, *next; + int ret = 0; + + QLIST_FOREACH_SAFE(notifier, &list->notifiers, node, next) { + ret = notifier->notify(notifier, data); + if (ret != 0) { + break; + } + } + return ret; +} |