Am 20.10.2023 um 13:39 schrieb Johannes Berg:
Sorry, but I did not get this. What may run past the schedule entry? Is your assumption, that the "thing" connected to stdin is always totally unaware of the time travel mode?On Fri, 2023-10-20 at 12:38 +0200, Benjamin Beichler wrote:Can you explain, why a time travel handler for stdin may be bad? It sounds like you want to avoid it, but I see no immediate problem.I need to read the thread, but this one's easy ;-) The thing is that on such a channel you don't send an ACK when you've seen that there's something to handle. As a result, the sender will continue running while you're trying to request a new schedule entry from the controller. As a result, it may run past your new schedule entry because it didn't know about it yet (this would likely bring down the controller and crash the simulation), or the relative order of the two entries is undefined, in the sense that it depends on the process scheduling of the host.
When our (to be published) simulation send something on serial lines (I think it does not matter whether it is a socket or a pipe), we expect that the uml instance needs to be run as long as it changes back to idle/wait state before the simulation time is advanced. Since the basis model of the time travel mode is, that you have infinite amount of processing power, the interrupt needs to be always handled at the current time.
Maybe my think-model only holds for "smaller" amounts of data (maybe one page or something?) or not the free-running mode, but I'm not completely convinced. :-D
Maybe we need to define, a bit more formally, how the (designed) processing model of interrupts in time travel mode is.
johannes _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um
OpenPGP_0x1569BBF90AC3918A.asc
Description: OpenPGP public key
OpenPGP_signature.asc
Description: OpenPGP digital signature
_______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um
