A method includes delivering a user-level interrupt message indicative of a user-level interrupt to one or more recipients according to a user-level interrupt delivery configuration selected from a plurality of user-level interrupt delivery configurations. The one or more recipients correspond to one or more application threads executing on one or more processor cores of a plurality of processor cores in a multi-core system. A method includes generating an indicator of a user-level interrupt being undeliverable to one or more intended recipients of a user-level interrupt message according to a failed delivery notification mode configuration. The user-level interrupt may be issued by an application thread executing on a first processor core of a plurality of processor cores in a multi-core system.