From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37518) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ur8SX-0003ka-D7 for qemu-devel@nongnu.org; Mon, 24 Jun 2013 11:13:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ur8SS-0004L5-OY for qemu-devel@nongnu.org; Mon, 24 Jun 2013 11:13:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12164) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ur8SS-0004Kk-Gc for qemu-devel@nongnu.org; Mon, 24 Jun 2013 11:13:32 -0400 From: Stefan Hajnoczi Date: Mon, 24 Jun 2013 17:13:09 +0200 Message-Id: <1372086800-4720-2-git-send-email-stefanha@redhat.com> In-Reply-To: <1372086800-4720-1-git-send-email-stefanha@redhat.com> References: <1372086800-4720-1-git-send-email-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH v6 01/12] notify: add NotiferWithReturn so notifier list can abort List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Fam Zheng , dietmar@proxmox.com, imain@redhat.com, Stefan Hajnoczi , Paolo Bonzini , xiawenc@linux.vnet.ibm.com 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 Reviewed-by: Kevin Wolf Signed-off-by: Stefan Hajnoczi --- include/qemu/notify.h | 29 +++++++++++++++++++++++++++++ util/notify.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 59 insertions(+) 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; +} -- 1.8.1.4