Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932642Ab2EDUrd (ORCPT ); Fri, 4 May 2012 16:47:33 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:34670 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932605Ab2EDUrV (ORCPT ); Fri, 4 May 2012 16:47:21 -0400 Message-Id: <20120504204229.240075699@linuxfoundation.org> User-Agent: quilt/0.60-19.1 Date: Fri, 04 May 2012 13:43:21 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Oleg Nesterov Subject: [ 57/75] exit_signal: simplify the "we have changed execution domain" logic In-Reply-To: <20120504204258.GA12552@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2758 Lines: 76 3.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov commit e636825346b36a07ccfc8e30946d52855e21f681 upstream. exit_notify() checks "tsk->self_exec_id != tsk->parent_exec_id" to handle the "we have changed execution domain" case. We can change do_thread() to always set ->exit_signal = SIGCHLD and remove this check to simplify the code. We could change setup_new_exec() instead, this looks more logical because it increments ->self_exec_id. But note that de_thread() already resets ->exit_signal if it changes the leader, let's keep both changes close to each other. Note that we change ->exit_signal lockless, this changes the rules. Thereafter ->exit_signal is not stable under tasklist but this is fine, the only possible change is OLDSIG -> SIGCHLD. This can race with eligible_child() but the race is harmless. We can race with reparent_leader() which changes our ->exit_signal in parallel, but it does the same change to SIGCHLD. The noticeable user-visible change is that the execing task is not "visible" to do_wait()->eligible_child(__WCLONE) right after exec. To me this looks more logical, and this is consistent with mt case. Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/exec.c | 3 +++ kernel/exit.c | 7 +------ 2 files changed, 4 insertions(+), 6 deletions(-) --- a/fs/exec.c +++ b/fs/exec.c @@ -975,6 +975,9 @@ static int de_thread(struct task_struct sig->notify_count = 0; no_thread_group: + /* we have changed execution domain */ + tsk->exit_signal = SIGCHLD; + if (current->mm) setmax_mm_hiwater_rss(&sig->maxrss, current->mm); --- a/kernel/exit.c +++ b/kernel/exit.c @@ -827,14 +827,9 @@ static void exit_notify(struct task_stru * If the parent exec id doesn't match the exec id we saved * when we started then we know the parent has changed security * domain. - * - * If our self_exec id doesn't match our parent_exec_id then - * we have changed execution domain as these two values started - * the same after a fork. */ if (thread_group_leader(tsk) && tsk->exit_signal != SIGCHLD && - (tsk->parent_exec_id != tsk->real_parent->self_exec_id || - tsk->self_exec_id != tsk->parent_exec_id)) + tsk->parent_exec_id != tsk->real_parent->self_exec_id) tsk->exit_signal = SIGCHLD; if (unlikely(tsk->ptrace)) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/