Re: context switch vs. signal delivery [was: Re: Accelerating user mode

From: Udo A. Steinberg (
Date: Tue Aug 06 2002 - 06:13:56 EST

On Tue, 06 Aug 2002 06:20:52 -0500
Jeff Dike <> wrote:

> said:
> > if (current->pgrp != -arg &&
> > current->pid != arg &&
> > !capable(CAP_KILL)) return(-EPERM);
> What's the problem here? This will let UML do F_SETOWN as well.

It will let the incoming process take over ownership of the socket,
which is probably what you mean and what you currently use.

I'm talking about a setup with the kernel residing in its own process.
On iret it would have to change ownership of the socket to another task,
i.e. process with kernel_pid wants to set task_pid as the owner of the
socket. The above code fragment doesn't permit this, as far as I can see.
What it does permit is the incoming task setting itself to the socket
owner, but that requires that the incoming task always runs a trampoline
first which accomplishes that.

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This archive was generated by hypermail 2b29 : Wed Aug 07 2002 - 22:00:31 EST