Re: Comparing "copy" and "map/unmap"

[Bas Wijnen]

On Mon, Oct 10, 2005 at 08:13:51PM -0400, Jonathan S. Shapiro wrote:
> On Tue, 2005-10-11 at 01:15 +0200, Matthieu Lemerre wrote:
> 
> > We want to be able to abort any blocking operation and this seemed to
> > be quite complex to manage in a server.  So Marcus came with the idea
> > of a notification server: instead of sending a message to the server
> > to tell it to abort the RPC, we could just have the thread stop
> > waiting for the notification server.  The server wouldn't even notice.
> 
> First question: who is "we"? If the client has paid for its resource,
> and wishes to block forever, it is none of the kernel's business (or the
> operating system). Of course, we must be able to destroy the storage
> when the owner wants it back, but this is a separate issue.
> 
> However, I think the case you mean is that the client wants a watchdog
> timer.

No.  It's about the following situation:
A client performs an RPC on a server S, which may block.
The user thinks it takes too long, and presses ctrl-c.
Now the RPC should be aborted.  However, simply cancelling the IPC would be a
protocol violation.

The proposed solution is to let a dedicated notification server wait for S,
which is prepared to have it's response fail (so cancelling the IPC in the
client is not a protocol violation).

Thanks,
Bas

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