Re: [PATCH -v5 00/17] Rewrite x86/ftrace to use text_poke (and more)

[Steven Rostedt]

On Mon, 25 Nov 2019 12:55:34 +0900
Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:

> void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
> ...
>         on_each_cpu(do_sync_core, NULL, 1);
>         /*
>          * sync_core() implies an smp_mb() and orders this store against
>          * the writing of the new instruction.
>          */
>         bp_patching.vec = NULL;
>         bp_patching.nr_entries = 0;
> }
> -----
> 
> I think the "on_each_cpu(do_sync_core, NULL, 1);" can sync the pipeline
> but doesn't ensure all ongoing int3 handling is done. Thus, we may need a

How does it not ensure all ongoing int3 handling is done? int3 is done
with interrupts disabled, and the on_each_cpu() requires all CPUs to
have had their interrupts enabled, thus int3 handling should be
completed. Perhaps we need another sync core?

	on_each_cpu(do_sync_core, NULL, 1);
	bp_patching.nr_entries = 0;
	on_each_cpu(do_sync_core, NULL, 1);
	bp_patching.vec = NULL;

?

-- Steve


> bigger wait in between bp_patching.nr_entries = 0 and bp_patching.vec = NULL;