Re: [PATCH] selinux: avoid atomic_t usage in sidtab

[Jann Horn <jannh@google.com>]

On Thu, Jul 25, 2019 at 3:59 PM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> As noted in Documentation/atomic_t.txt, if we don't need the RMW atomic
> operations, we should only use READ_ONCE()/WRITE_ONCE() +
> smp_rmb()/smp_wmb() where necessary (or the combined variants
> smp_load_acquire()/smp_store_release()).
>
> This patch converts the sidtab code to use regular u32 for the counter
> and reverse lookup cache and use the appropriate operations instead of
> atomic_get()/atomic_set(). Note that when reading/updating the reverse
> lookup cache we don't need memory barriers as it doesn't need to be
> consistent or accurate. We can now also replace some atomic ops with
> regular loads (when under spinlock) and stores (for conversion target
> fields that are always accessed under the master table's spinlock).
>
> We can now also bump SIDTAB_MAX to U32_MAX as we can use the full u32
> range again.
>
> Suggested-by: Jann Horn <jannh@google.com>
> Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>

Looks good to me; you can add "Reviewed-by: Jann Horn
<jannh@google.com>" if you want.