Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752711AbcDRLiU (ORCPT ); Mon, 18 Apr 2016 07:38:20 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:25752 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752066AbcDRLiS (ORCPT ); Mon, 18 Apr 2016 07:38:18 -0400 Message-ID: <5714C536.4070308@huawei.com> Date: Mon, 18 Apr 2016 19:29:58 +0800 From: Joseph Qi User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: CC: , , Joel Becker , Mark Fasheh , Junxiao Bi , Andrew Morton , "Linus Torvalds" , Zefan Li Subject: Re: [PATCH 3.4 61/92] ocfs2/dlm: fix deadlock when dispatch assert master References: <1460976338-5631-1-git-send-email-lizf@kernel.org> <1460976397-5688-61-git-send-email-lizf@kernel.org> In-Reply-To: <1460976397-5688-61-git-send-email-lizf@kernel.org> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.22.101] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3446 Lines: 105 Hi Zefan, In dlm_master_request_handler, it has missed the following change : - dlm_put(dlm); + if (!dispatched) + dlm_put(dlm); Thanks, Joseph On 2016/4/18 18:46, lizf@kernel.org wrote: > From: Joseph Qi > > 3.4.112-rc1 review patch. If anyone has any objections, please let me know. > > ------------------ > > > commit 012572d4fc2e4ddd5c8ec8614d51414ec6cae02a upstream. > > The order of the following three spinlocks should be: > dlm_domain_lock < dlm_ctxt->spinlock < dlm_lock_resource->spinlock > > But dlm_dispatch_assert_master() is called while holding > dlm_ctxt->spinlock and dlm_lock_resource->spinlock, and then it calls > dlm_grab() which will take dlm_domain_lock. > > Once another thread (for example, dlm_query_join_handler) has already > taken dlm_domain_lock, and tries to take dlm_ctxt->spinlock deadlock > happens. > > Signed-off-by: Joseph Qi > Cc: Joel Becker > Cc: Mark Fasheh > Cc: "Junxiao Bi" > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds > [lizf: Backported to 3.4: adjust context] > Signed-off-by: Zefan Li > --- > fs/ocfs2/dlm/dlmmaster.c | 4 +++- > fs/ocfs2/dlm/dlmrecovery.c | 6 +++++- > 2 files changed, 8 insertions(+), 2 deletions(-) > > diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c > index 7ba6ac1..751efa8 100644 > --- a/fs/ocfs2/dlm/dlmmaster.c > +++ b/fs/ocfs2/dlm/dlmmaster.c > @@ -1411,6 +1411,7 @@ int dlm_master_request_handler(struct o2net_msg *msg, u32 len, void *data, > int found, ret; > int set_maybe; > int dispatch_assert = 0; > + int dispatched = 0; > > if (!dlm_grab(dlm)) > return DLM_MASTER_RESP_NO; > @@ -1617,6 +1618,8 @@ send_response: > mlog(ML_ERROR, "failed to dispatch assert master work\n"); > response = DLM_MASTER_RESP_ERROR; > dlm_lockres_put(res); > + } else { > + dispatched = 1; > } > } else { > if (res) > @@ -2041,7 +2044,6 @@ int dlm_dispatch_assert_master(struct dlm_ctxt *dlm, > > > /* queue up work for dlm_assert_master_worker */ > - dlm_grab(dlm); /* get an extra ref for the work item */ > dlm_init_work_item(dlm, item, dlm_assert_master_worker, NULL); > item->u.am.lockres = res; /* already have a ref */ > /* can optionally ignore node numbers higher than this node */ > diff --git a/fs/ocfs2/dlm/dlmrecovery.c b/fs/ocfs2/dlm/dlmrecovery.c > index d15b071..0e5013e 100644 > --- a/fs/ocfs2/dlm/dlmrecovery.c > +++ b/fs/ocfs2/dlm/dlmrecovery.c > @@ -1689,6 +1689,7 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data, > unsigned int hash; > int master = DLM_LOCK_RES_OWNER_UNKNOWN; > u32 flags = DLM_ASSERT_MASTER_REQUERY; > + int dispatched = 0; > > if (!dlm_grab(dlm)) { > /* since the domain has gone away on this > @@ -1710,6 +1711,8 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data, > mlog_errno(-ENOMEM); > /* retry!? */ > BUG(); > + } else { > + dispatched = 1; > } > } else /* put.. incase we are not the master */ > dlm_lockres_put(res); > @@ -1717,7 +1720,8 @@ int dlm_master_requery_handler(struct o2net_msg *msg, u32 len, void *data, > } > spin_unlock(&dlm->spinlock); > > - dlm_put(dlm); > + if (!dispatched) > + dlm_put(dlm); > return master; > } > >