Data cache flush guaranteed to complete before returning?

Hi,

I'm working with a multi nios-ii implementation where there is a shared off-chip memory bank. Access to the shared memory is protected with a mutex across the CPUs and the DCACHE is enabled on the processors. If I call alt_flush_cache() before releasing the mutex am I guaranteed that the flush was actually completed before the alt_flush_chache() call returns (as opposed to just informing the dcache but not waiting for it to complete the flush back to memory)?

Thanks!