On 07/28/2009 08:55 PM, Michael S. Tsirkin wrote:
This implements a new EFD_STATE flag for eventfd. When set, this flag changes eventfd behaviour in the following way: - write simply stores the value written, and is always non-blocking - read unblocks when the value written changes, and returns the value writtenMotivation: we'd like to use eventfd in qemu to pass interrupts from (emulated or assigned) devices to guest. For level interrupts, the counter supported currently by eventfd is not a good match: we really need to set interrupt to a level, typically 0 or 1, and give the guest ability to see the last value written. @@ -31,37 +31,59 @@ struct eventfd_ctx { * issue a wakeup. */ __u64 count; + /* + * When EF_STATE flag is set, eventfd behaves differently: + * value written gets stored in "count", read will copy + * "count" to "state". + */ + __u64 state; unsigned int flags; };
Why not write the new value into ->count directly? -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
