Re: [patch V3 01/32] mm/slab: Fix broken stack trace storage

Andy Lutomirski
2019-04-15T16:58:20Z

On Sun, Apr 14, 2019 at 9:34 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Sun, 14 Apr 2019, Andy Lutomirski wrote:
> > > + struct stack_trace trace = {
> > > + .max_entries = size - 4;
> > > + .entries = addr;
> > > + .skip = 3;
> > > + };
> >
> > This looks correct, but I think that it would have been clearer if you
> > left the size -= 3 above. You're still incrementing addr, but you're
> > not decrementing size, so they're out of sync and the resulting code
> > is hard to follow.
>
> What about the below?
>
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -1480,10 +1480,12 @@ static void store_stackinfo(struct kmem_
> *addr++ = 0x12345678;
> *addr++ = caller;
> *addr++ = smp_processor_id();
> + size -= 3;
> #ifdef CONFIG_STACKTRACE
> {
> struct stack_trace trace = {
> - .max_entries = size - 4;
> + /* Leave one for the end marker below */
> + .max_entries = size - 1;
> .entries = addr;
> .skip = 3;
> };

Looks good to me.