Disabling interrupt to achieve mutual exclusion?

[tongc]

Hi! Could anyone tell me why disabling interupts to achieve mutual exclusion is not acceptable on a multiprocessor sytem??? Thanks

[Phil Speller]

Well, the first thing that springs to mind is that you can't arbitrate access to any external shared resources with this method e.g. shared RAM. However, the use of something like a Semaphore in the context of a multi-processor kernel would allow this. In general, it is always best to think twice about disabling interrupts to implement mutual exlusion since any time spent in this state will increase interrupt latency - which may not be desirable. Phil