On Thu, 2009-11-19 at 13:05 +0100, Jean Delvare wrote: > > Was yield() turned into NOOP by design, or was it a bug? Design. yield() for SCHED_OTHER is not specified, so everything goes. There's two possible 'sane' options for yield for (CFS's) SCHED_OTHER: - place the task behind all other tasks of the same nice level This is however an O(n) operation for CFS since we don't separate things out based on nice level, hence we don't do that. - service the task that is most starved of service That fits nicely into the fairness thing, and is what we default to. The thing is, that's current in 99% of the cases, otherwise we would already be running another task. So its not strictly a NOP, but in practice it is. There is also another option, place the task behind _all_ other tasks, but that also surprises people and causes regressions, because they don't expect yield() to wait _that_ long. And all this is irrespective of the question of whether yield() is ever a sane thing to do (I say not). -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
