Re: [PATCH 2/2] utrace: ptrace cooperation

[Christoph Hellwig <hch@infradead.org>]

On Tue, Aug 26, 2008 at 03:02:37PM -0700, Roland McGrath wrote:
> 
> This adds the CONFIG_UTRACE_PTRACE option under CONFIG_UTRACE.
> When set, parts of ptrace are replaced so it uses the utrace
> facilities for noticing events, stopping and resuming threads.
> 
> This makes ptrace play nicely with other utrace-based things
> tracing the same threads.  It also makes all ptrace uses rely on
> some of the utrace code working right, even when you are not
> using any other utrace-based things.  So it's experimental and
> not real well proven yet.  But it's recommended if you enable
> CONFIG_UTRACE and want to try new utrace things.

I don't like this patch in it's current form.  Having two different ways
to do ptrace is a rather awkward thing and not very good for testing
coverage.  This should not be an option but required.  I'm not even sure
keeping a non-utrace version at all is a good idea. I'd rather set a
deadline for arch maintainers to convert everything to the generic
ptrace bits + regsets + tracehook and if they don't manage to do it by
then ptrace will be disabled for those who can't keep up.  Of course
this will need an announcement on linux-arch first, but it's much better
than a never ending phase of APIs in migration.