Re: no-copy ipc

On Mon Jan 22, 2007 at 20:33:39 +0000, bahadir balban wrote:
>Hi,
>
>How does L4 ensure ipc occurs without copying?
>
>Suppose a sender (S), receiver (R) and an other process (O) is running
>on the system. I would think that during the ipc context switch from
>(S) to (R), registers don't need to be pushed to memory and read back,
>which stands for the "no-copy" part of ipc. Is that correct? If so,
>the system must ensure no context switch to some (O) occurs during the
>time which the message registers are passed from (S) to (R). Would you
>agree? Or am I confusing ipc copying with context switch overhead?

IPC is an atomic operation, so a context switch to O cannot occur
during an IPC between S and R.

Cheers,

Benno