kernel/pid.c: improve flow of a loop inside alloc_pidmap.
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.
[akpm@linux-foundation.org: simplify code]
Signed-off-by: Raphael S. Carvalho <raphael.scarv@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/pid.c b/kernel/pid.c
index 047dc62..8147bdf 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -183,15 +183,19 @@
break;
}
if (likely(atomic_read(&map->nr_free))) {
- do {
+ 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);
- } while (offset < BITS_PER_PAGE && pid < pid_max);
+ if (pid >= pid_max)
+ break;
+ }
}
if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
++map;