revert "proc: fix the threaded proc self"

Revert commit c6caeb7c4544608e8ae62731334661fc396c7f85 ("proc: fix the
threaded /proc/self"), since Eric says "The patch really is wrong.
There is at least one corner case in procps that cares."

Cc: Eric W. Biederman <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: "Guillaume Chazarain" <[e-mail]>
Cc: "Pavel Emelyanov" <[e-mail]>
Cc: "Rafael J. Wysocki" <[e-mail]>
Cc: Oleg Nesterov <[e-mail]>
Cc: Roland McGrath <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/proc/base.c

···
 			      int buflen)
 {
 	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
-	pid_t pid = task_pid_nr_ns(current, ns);
+	pid_t tgid = task_tgid_nr_ns(current, ns);
 	char tmp[PROC_NUMBUF];
-	if (!pid)
+	if (!tgid)
 		return -ENOENT;
-	sprintf(tmp, "%d", pid);
+	sprintf(tmp, "%d", tgid);
 	return vfs_readlink(dentry,buffer,buflen,tmp);
 }
 
 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
 	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
-	pid_t pid = task_pid_nr_ns(current, ns);
+	pid_t tgid = task_tgid_nr_ns(current, ns);
 	char tmp[PROC_NUMBUF];
-	if (!pid)
+	if (!tgid)
 		return ERR_PTR(-ENOENT);
-	sprintf(tmp, "%d", pid);
+	sprintf(tmp, "%d", task_tgid_nr_ns(current, ns));
 	return ERR_PTR(vfs_follow_link(nd,tmp));
 }