On Wed, 1 Mar 2023 20:18:11 +0100
Uros Bizjak <ubizjak@xxxxxxxxx> wrote:
> If we want to put the definition in generic headers, then we also need
> to define acquire/release/relaxed and 64bit variants. ATM, we have two
> sites that require this definition and I think that for now we could
> live with two instances of the same definition in two separate
> subsystems. But this would definitely be a good future addition. There
> is some code in the form of
>
> if (cmpxchg (ptr, 0, 1) == 0)
>
> that can not be converted to try_cmpxchg, but can use cmpxchg_success.
And even modify code that uses temp variables. For example, where you
modified the ring buffer code to use try_cmpxchg(), I could convert your:
static int rb_head_page_replace(struct buffer_page *old,
struct buffer_page *new)
{
unsigned long *ptr = (unsigned long *)&old->list.prev->next;
unsigned long val;
val = *ptr & ~RB_FLAG_MASK;
val |= RB_PAGE_HEAD;
return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
}
Into just:
static int rb_head_page_replace(struct buffer_page *old,
struct buffer_page *new)
{
unsigned long *ptr = (unsigned long *)&old->list.prev->next;
unsigned long val;
val = *ptr & ~RB_FLAG_MASK;
return cmpxchg_success(ptr, val | RB_PAGE_HEAD, (unsigned long)&new->list);
}
-- Steve
