On Mon, 11 Mar 2013 18:18:56 -0300 "Raphael S. Carvalho"
<raphael.sc...@gmail.com> wrote:
> From: Raphael S.Carvalho <raphael.sc...@gmail.com>
>
> Notes: find_next_offset searches for an available "cleaned bit"
> in the respective pid bitmap (page), so returns the offset if found,
> otherwise it returns a value equals to BITS_PER_PAGE.
>
> For example, suppose find_next_offset didn't find any available
> bit, so there's no purpose to call mk_pid (Wasteful Cpu Cycles).
>
> Therefore, I found it could be better to call mk_pid after
> the checking (offset < BITS_PER_PAGE) returned sucessfully!
> Another point: If (offset < BITS_PER_PAGE) results in a "failure",
> then mk_pid would be called again afterwards.
>
> ...
>
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -190,8 +190,8 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
> return pid;
> }
> offset = find_next_offset(map, offset);
> - pid = mk_pid(pid_ns, map, offset);
> - } while (offset < BITS_PER_PAGE && pid < pid_max);
> + } while (offset < BITS_PER_PAGE &&
> + (pid = mk_pid(pid_ns, map, offset)) < pid_max);
> }
> if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
> ++map;
Looks OK. But I think it's simpler and more straightforward to do it
this way?
for ( ; ; ) {
if (!test_and_set_bit(offset, map->page)) {
atomic_dec(&map->nr_free);
set_last_pid(pid_ns, last, pid);
return pid;
}
offset = find_next_offset(map, offset);
if (offset >= BITS_PER_PAGE)
break;
pid = mk_pid(pid_ns, map, offset);
if (pid >= pid_max)
break;
}
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