On Mon, Jan 11, 2010 at 11:02:27AM +0200, Michael S. Tsirkin wrote: > On Mon, Jan 11, 2010 at 11:01:27AM +0200, Gleb Natapov wrote: > > On Thu, Jan 07, 2010 at 12:36:01PM +0200, Michael S. Tsirkin wrote: > > > Or if I do it the other way: > > > remove_wait_queue(irqfd->wqh, &irqfd->wait); > > > -> > > > eventfd_read_ctx(irqfd->eventfd, &ucnt); > > > > > > now, if device signals eventfd at point marked by ->, > > > it will not be sent but counter will be cleared, > > > so we will loose a message. > > > > > May be I am missing something here, but why doing it like that is a > > problem? Event delivery races with interrupt masking so making masking > > succeed before event delivery is OK. Event generation is asynchronous > > anyway and could have happened jiffy latter anyway. > > > > -- > > Gleb. > > No, event generation would only trigger a single interrupt. This race > generates two interrupts for a single event. This can never happen with > real hardware. eventfd_ctx_remove_wait_queue would solve this problem. > In quoted test above you are saying that "we will loose a message". So how does it generates two interrupts when we loose a message? -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
