Re: next steps

["Frank Ch. Eigler" <fche@redhat.com>]

Hi -

> Frank, under improving kprobes I would add:

Thanks for the suggestions.

> 1) dprobes or a scalable mechanism for performance tracing [...]

Could you elaborate on what exactly "scalable ... tracing" refers to,
and how you believe we're short of this?

> 2) watchpoint probes if these aren't already there. [...]

This is already tracked by bug #1324.  A prerequisite is a debug
register management API in the kernel.

> 3) add back the ability to place probes in a code location before
> the module is loaded. [...]  We used to have this capability for
> kernel modules. It relied on patches in insmod. Clearly this is
> useful especially when wanting to capture initialization module
> problems.

Sounds useful, especially if it can be accomplished without much or
any patching of generic kernel or kernel-utils code.  Might the
register_module_notifier() hook be sufficient for this?  It's worth
creating a bugzilla item for this.  Bug #1145 is a prerequisite.

> 4) Finally I'd request that we re-instate the SysRq function to
> disable all probes instantly. [...]

Please create a bugzilla item.  __sysrq_put_key_op is probably
suitable, as long as a handler doesn't try to do much anything fancy.
Is it safe to instantly remove all kprobes at an arbitrary moment?

> Apart from 1) all of these are simple modification for which the
> code has all ready been written.

These are good, though was intending to list the *larger* missing
chunks: leaps of usefulness that would excite ordinary developers, not
just kernel hackers.


- FChE