Trouble with creating multiprocessor Nios II system with shared memory

I'm not familiar enough with the example design but my first impression is the same as Daixiwen's. It sounds like the first two cpu's are beating out the other two when aquiring the mutex. If you want some mechanism to ensure everyone gets a fair shot at it, you're going to have to add it.

If you want to verify that the other processors can indeed get the mutex, you can run all processor's in the debugger, then pause the first two and see if the other processors are able to get the mutex.

Jake