From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759540AbXIXRrS (ORCPT ); Mon, 24 Sep 2007 13:47:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755481AbXIXRrF (ORCPT ); Mon, 24 Sep 2007 13:47:05 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.141]:35937 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753938AbXIXRrC (ORCPT ); Mon, 24 Sep 2007 13:47:02 -0400 Subject: [PATCH] make lockdep happy with r/o bind mounts To: akpm@osdl.org Cc: linux-kernel@vger.kernel.org, adobriyan@sw.ru, peterz@infradead.org, Dave Hansen From: Dave Hansen Date: Mon, 24 Sep 2007 10:46:58 -0700 Message-Id: <20070924174658.2B3D54B8@kernel> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org With the r/o bind mount patches, we can have as many spinlocks nested as there are CPUs on the system. Lockdep freaks out after 8. So, create a new lockdep class of locks for the mnt_writer spinlocks, and initialize each of the cpu locks to be in a different class. It should shut up warnings like this, while still allowing some of the lockdep goodness to remain: ============================================= [ INFO: possible recursive locking detected ] 2.6.23-rc6 #6 --------------------------------------------- swapper/1 is trying to acquire lock: (&writer->lock){--..}, at: [] lock_and_coalesce_cpu_mnt_writer_counts+0x29/0x5c but task is already holding lock: (&writer->lock){--..}, at: [] lock_and_coalesce_cpu_mnt_writer_counts+0x29/0x5c other info that might help us debug this: 1 lock held by swapper/1: #0: (&writer->lock){--..}, at: [] lock_and_coalesce_cpu_mnt_writer_counts+0x29/0x5c stack backtrace: [] show_trace_log_lvl+0x19/0x2e [] show_trace+0x12/0x14 [] dump_stack+0x14/0x16 [] print_deadlock_bug+0xb7/0xc1 [] check_deadlock+0x40/0x54 [] validate_chain+0x26e/0x319 [] __lock_acquire+0x6c4/0x731 [] lock_acquire+0x7a/0x94 [] _spin_lock+0x38/0x62 [] lock_and_coalesce_cpu_mnt_writer_counts+0x29/0x5c [] mntput_no_expire+0x38/0xad [] path_release_on_umount+0x15/0x18 [] sys_umount+0x67/0x6f [] name_to_dev_t+0x22a/0x24c [] prepare_namespace+0x89/0x187 [] kernel_init+0x9a/0xa3 [] kernel_thread_helper+0x7/0x10 ======================= Signed-off-by: Dave Hansen --- lxc-dave/fs/namespace.c | 2 ++ 1 file changed, 2 insertions(+) diff -puN fs/namespace.c~make-lockdep-happy-with-ro-bind-mounts fs/namespace.c --- lxc/fs/namespace.c~make-lockdep-happy-with-ro-bind-mounts 2007-09-24 10:32:23.000000000 -0700 +++ lxc-dave/fs/namespace.c 2007-09-24 10:41:37.000000000 -0700 @@ -116,6 +116,7 @@ struct mnt_writer { * must be ordered by cpu number. */ spinlock_t lock; + struct lock_class_key lock_class; /* compiles out with !lockdep */ unsigned long count; struct vfsmount *mnt; } ____cacheline_aligned_in_smp; @@ -127,6 +128,7 @@ static int __init init_mnt_writers(void) for_each_possible_cpu(cpu) { struct mnt_writer *writer = &per_cpu(mnt_writers, cpu); spin_lock_init(&writer->lock); + lockdep_set_class(&writer->lock, &writer->lock_class); writer->count = 0; } return 0; diff -puN include/linux/lockdep.h~make-lockdep-happy-with-ro-bind-mounts include/linux/lockdep.h _