On Wed, 2010-09-15 at 18:20 +0200, David Kastrup wrote: > Nivedita Singhvi <niv@xxxxxxxxxx> writes: > > A hardware failure means that the system is in violation of the system > design. A soft realtime failure means that reality is in violation of > the system design. The PREEMPT_RT patch (as I explained in another email) is designed to be hard real time. Thus, a failure to meet its deadline is a failure in the system design, just like it would be for hardware. If you have a extremely complex piece of equipment, it is very hard to prove that it can meet its deadlines given all circumstances. One reason that x86 is not very hard real time friendly. The same is true with software. If it becomes complex, it is very hard to prove that it too can meet its deadlines in all corner cases. The analogy still holds true. Hardware that is less complex is easier to mathematically prove that it will do what you expect to do in all cases, than hardware that is over engineered, just like software. I hold that PREEMPT_RT is not soft real time, but is hard real time designed. That is, we can't prove that it is hard real time, but any time we find a case that the software can break its deterministic result, it is a bug and needs to be fixed. (aka, a system failure). -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
