From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756551AbYGCUvU (ORCPT ); Thu, 3 Jul 2008 16:51:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753277AbYGCUvK (ORCPT ); Thu, 3 Jul 2008 16:51:10 -0400 Received: from extu-mxob-1.symantec.com ([216.10.194.28]:60814 "EHLO extu-mxob-1.symantec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753029AbYGCUvJ (ORCPT ); Thu, 3 Jul 2008 16:51:09 -0400 Date: Thu, 3 Jul 2008 21:50:31 +0100 (BST) From: Hugh Dickins X-X-Sender: hugh@blonde.site To: Andrew Morton cc: Balbir Singh , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 2.6.26-rc8-mm1] memrlimit: fix mmap_sem deadlock Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "ps -f" hung after "killall make" of make -j20 kernel builds. It's generally considered bad manners to down_write something you already have down_read. exit_mm up_reads before calling mm_update_next_owner, so I guess exec_mmap can safely do so too. (And with that repositioning there's not much point in mm_need_new_owner allowing for NULL mm.) Signed-off-by: Hugh Dickins --- Fix to memrlimit-cgroup-mm-owner-callback-changes-to-add-task-info.patch quite independent of its recent sleeping-inside-spinlock fix; could even be applied to 2.6.26, though no deadlock there. Gosh, I see those patches have spawned "Reviewed-by" tags in my name: sorry, no, just "Bug-found-by". fs/exec.c | 2 +- kernel/exit.c | 2 -- 2 files changed, 1 insertion(+), 3 deletions(-) --- 2.6.26-rc8-mm1/fs/exec.c 2008-07-03 11:35:20.000000000 +0100 +++ linux/fs/exec.c 2008-07-03 20:27:20.000000000 +0100 @@ -738,11 +738,11 @@ static int exec_mmap(struct mm_struct *m tsk->active_mm = mm; activate_mm(active_mm, mm); task_unlock(tsk); - mm_update_next_owner(old_mm); arch_pick_mmap_layout(mm); if (old_mm) { up_read(&old_mm->mmap_sem); BUG_ON(active_mm != old_mm); + mm_update_next_owner(old_mm); mmput(old_mm); return 0; } --- 2.6.26-rc8-mm1/kernel/exit.c 2008-07-03 11:35:37.000000000 +0100 +++ linux/kernel/exit.c 2008-07-03 20:28:35.000000000 +0100 @@ -588,8 +588,6 @@ mm_need_new_owner(struct mm_struct *mm, * If there are other users of the mm and the owner (us) is exiting * we need to find a new owner to take on the responsibility. */ - if (!mm) - return 0; if (atomic_read(&mm->mm_users) <= 1) return 0; if (mm->owner != p)