On 06/09, Andrea Parri wrote:
>
> There is no need to use the barrier if there is no dereference/
> memory access; move it where needed (currently, affecting only
> Alpha).
OK, although area == NULL is unlikely case,
> While touching this, also make the reads _ONCE().
Why? both xol_area/vaddr can't change.
> Signed-off-by: Andrea Parri <parri.and...@gmail.com>
> ---
> kernel/events/uprobes.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index b7a525ab2083..b1364acd683e 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1520,10 +1520,11 @@ static unsigned long get_trampoline_vaddr(void)
> struct xol_area *area;
> unsigned long trampoline_vaddr = -1;
>
> - area = current->mm->uprobes_state.xol_area;
> - smp_read_barrier_depends();
> - if (area)
> - trampoline_vaddr = area->vaddr;
> + area = READ_ONCE(current->mm->uprobes_state.xol_area);
> + if (area) {
> + smp_read_barrier_depends();
> + trampoline_vaddr = READ_ONCE(area->vaddr);
> + }
>
> return trampoline_vaddr;
> }
> --
> 1.9.1
>
