Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751394AbaKGDY3 (ORCPT ); Thu, 6 Nov 2014 22:24:29 -0500 Received: from szxga01-in.huawei.com ([119.145.14.64]:15994 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751051AbaKGDY1 (ORCPT ); Thu, 6 Nov 2014 22:24:27 -0500 From: Yijing Wang To: CC: , , , Yijing Wang , Weng Meiling , Subject: [PATCH] sysfs: driver core: Fix glue dir race condition by gdp_mutex Date: Fri, 7 Nov 2014 12:05:49 +0800 Message-ID: <1415333149-13099-1-git-send-email-wangyijing@huawei.com> X-Mailer: git-send-email 1.7.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.100.166] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is a race condition when removing glue directory. It can be reproduced in following test: path 1: Add first child device device_add() get_device_parent() /*find parent from glue_dirs.list*/ list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry) if (k->parent == parent_kobj) { kobj = kobject_get(k); break; } .... class_dir_create_and_add() path2: Remove last child device under glue dir device_del() cleanup_device_parent() cleanup_glue_dir() kobject_put(glue_dir); If path2 has been called cleanup_glue_dir(), but not call kobject_put(glue_dir), the glue dir is still in parent's kset list. Meanwhile, path1 find the glue dir from the glue_dirs.list. Path2 may release glue dir before path1 call kobject_get(). So kernel will report the warning and bug_on. This is a "classic" problem we have of a kref in a list that can be found while the last instance could be removed at the same time. This patch reuse gdp_mutex to fix this race condition. The following calltrace is captured in kernel 3.4, but the latest kernel still has this bug. ----------------------------------------------------- <4>[ 3965.441471] WARNING: at ...include/linux/kref.h:41 kobject_get+0x33/0x40() <4>[ 3965.441474] Hardware name: Romley <4>[ 3965.441475] Modules linked in: isd_iop(O) isd_xda(O)... ... <4>[ 3965.441605] Call Trace: <4>[ 3965.441611] [] warn_slowpath_common+0x7a/0xb0 <4>[ 3965.441615] [] warn_slowpath_null+0x15/0x20 <4>[ 3965.441618] [] kobject_get+0x33/0x40 <4>[ 3965.441624] [] get_device_parent.isra.11+0x135/0x1f0 <4>[ 3965.441627] [] device_add+0xd4/0x6d0 <4>[ 3965.441631] [] ? dev_set_name+0x3c/0x40 .... <2>[ 3965.441912] kernel BUG at ..../fs/sysfs/group.c:65! <4>[ 3965.441915] invalid opcode: 0000 [#1] SMP ... <4>[ 3965.686743] [] sysfs_create_group+0xe/0x10 <4>[ 3965.686748] [] blk_trace_init_sysfs+0x14/0x20 <4>[ 3965.686753] [] blk_register_queue+0x3b/0x120 <4>[ 3965.686756] [] add_disk+0x1cc/0x490 .... ------------------------------------------------------- Signed-off-by: Yijing Wang Signed-off-by: Weng Meiling Cc: #3.4+ --- drivers/base/core.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 14d1629..842d047 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -724,12 +724,12 @@ class_dir_create_and_add(struct class *class, struct kobject *parent_kobj) return &dir->kobj; } +static DEFINE_MUTEX(gdp_mutex); static struct kobject *get_device_parent(struct device *dev, struct device *parent) { if (dev->class) { - static DEFINE_MUTEX(gdp_mutex); struct kobject *kobj = NULL; struct kobject *parent_kobj; struct kobject *k; @@ -793,7 +793,9 @@ static void cleanup_glue_dir(struct device *dev, struct kobject *glue_dir) glue_dir->kset != &dev->class->p->glue_dirs) return; + mutex_lock(&gdp_mutex); kobject_put(glue_dir); + mutex_unlock(&gdp_mutex); } static void cleanup_device_parent(struct device *dev) -- 1.7.1 -- 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/