[PATCH] sys_setpgid: eliminate unnecessary do_each_task_pid(PIDTYPE_PGID)

All tasks in the process group have the same sid, we don't need to iterate
them all to check that the caller of sys_setpgid() doesn't change its
session.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/kernel/sys.c b/kernel/sys.c
index 4f9d23a..c7675c1 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1397,16 +1397,13 @@ asmlinkage long sys_setpgid(pid_t pid, pid_t pgid)
                goto out;
 
        if (pgid != pid) {
-               struct task_struct *p;
+               struct task_struct *g =
+                       find_task_by_pid_type(PIDTYPE_PGID, pgid);
 
-               do_each_task_pid(pgid, PIDTYPE_PGID, p) {
-                       if (process_session(p) == process_session(group_leader))
-                               goto ok_pgid;
-               } while_each_task_pid(pgid, PIDTYPE_PGID, p);
-               goto out;
+               if (!g || process_session(g) != process_session(group_leader))
+                       goto out;
        }
 
-ok_pgid:
        err = security_task_setpgid(p, pgid);
        if (err)
                goto out;