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SubjectRe: [PATCH v3 5/6] x86/ftrace: Use text_poke()
On Thu, 10 Oct 2019 11:20:54 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, Oct 09, 2019 at 10:41:35PM -0400, Steven Rostedt wrote:
> > On Tue, 8 Oct 2019 10:43:35 -0400
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> >
> > > BTW, I'd really like to take this patch series through my tree. That
> > > way I can really hammer it, as well as I have code that will be built
> > > on top of it.
> >
> > I did a bit of hammering and found two bugs. One I sent a patch to fix
> > (adding a module when tracing is enabled), but the other bug I
> > triggered, I'm too tired to debug right now. But figured I'd mention it
> > anyway.
>
> I'm thinking this should fix it... Just not sure this is the right plce,
> then again, we're doing the same thing in jump_label and static_call, so
> perhaps we should do it like this.
>
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -1230,10 +1230,15 @@ void text_poke_queue(void *addr, const v
> * dynamically allocated memory. This function should be used when it is
> * not possible to allocate memory.
> */
> -void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate)
> +void __ref text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate)
> {
> struct text_poke_loc tp;
>
> + if (unlikely(system_state == SYSTEM_BOOTING)) {
> + text_poke_early(addr, opcode, len);
> + return;
> + }

We need a new system state. SYSTEM_UP ? (Arg, that name is confusing,
SYSTEM_BOOTING_SMP?) Or perhaps just test num_online_cpus()?

if (unlikely(system_state == SYSTEM_BOOTING &&
num_online_cpus() == 1)

?

Because we can't do the above once we have more than one CPU running.

-- Steve

> +
> text_poke_loc_init(&tp, addr, opcode, len, emulate);
> text_poke_bp_batch(&tp, 1);
> }

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