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authorRaphael S. Carvalho <raphael.scarv@gmail.com>2013-04-30 15:28:26 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-04-30 17:04:07 -0700
commit8db049b3d666b3676ff4a976e03c14de302bf9fa (patch)
tree74d5e5c8e25b451e983e66cb1e2a41cbf8e1b4f1
parentc75aaa8ed03eb1312ed2990f1a716b2b9cc0df42 (diff)
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>
-rw-r--r--kernel/pid.c8
1 files changed, 6 insertions, 2 deletions
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 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
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;