Re: [patch 12/12] Tracepoints - Immediate Values

Mathieu Desnoyers
2009-09-24T15:03:33Z

* Peter Zijlstra (peterz@infradead.org) wrote:
> On Thu, 2009-09-24 at 09:26 -0400, Mathieu Desnoyers wrote:
> > plain text document attachment (tracepoints-immediate-values.patch)
> > Use immediate values in tracepoints.
>
> I might have missed it, but did both the Intel and AMD cpu folks clear
> the SMP code rewrite bits?
>

SMP handling is performed with stop_machine() in this patchset. Nothing
fancy here.

I've got other patches, not included in this patchset, which implements
nmi-safe code modification, based on a scheme using breakpoints and
IPIs, inspired from djprobes. That one might be worth clearing with
intel/amd devs before merging.

However, doing code patching within stop_machine() is pretty safe, given
all other CPUs are busy-looping with interrupts off while this happens.
Ftrace already does this.

Thanks,

Mathieu