From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiubo Li Subject: Re: [PATCH] ceph: make sure the mdsc->mutex is nested in s->s_mutex to fix dead lock Date: Wed, 27 May 2020 21:53:21 +0800 Message-ID: <3c9830fb-018a-e3e5-d0cc-2863a9cd375b@redhat.com> References: <1589961079-27932-1-git-send-email-xiubli@redhat.com> <17832c6b42a2f3876190d8e85ce0380a0f38f541.camel@kernel.org> <6be48ac4-6743-e328-c1bf-fe2a8639a655@redhat.com> <622107f91d3d5b93aa14aeace05cf97213dc8b60.camel@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from us-smtp-2.mimecast.com ([207.211.31.81]:29082 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388713AbgE0Nxc (ORCPT ); Wed, 27 May 2020 09:53:32 -0400 In-Reply-To: <622107f91d3d5b93aa14aeace05cf97213dc8b60.camel@kernel.org> Content-Language: en-US Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Jeff Layton , Ilya Dryomov Cc: "Yan, Zheng" , Patrick Donnelly , Ceph Development On 2020/5/27 21:47, Jeff Layton wrote: > On Wed, 2020-05-27 at 20:47 +0800, Xiubo Li wrote: >> On 2020/5/27 20:25, Ilya Dryomov wrote: >>> On Wed, May 20, 2020 at 1:44 PM Jeff Layton wrote: >>>> On Wed, 2020-05-20 at 03:51 -0400, xiubli@redhat.com wrote: >>>>> From: Xiubo Li >>>>> >>>>> The call trace: >>>>> >>>>> <6>[15981.740583] libceph: mon2 (1)10.72.36.245:40083 session lost, hunting for new mon >>>>> <3>[16097.960293] INFO: task kworker/18:1:32111 blocked for more than 122 seconds. >>>>> <3>[16097.960860] Tainted: G E 5.7.0-rc5+ #80 >>>>> <3>[16097.961332] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >>>>> <6>[16097.961868] kworker/18:1 D 0 32111 2 0x80004080 >>>>> <6>[16097.962151] Workqueue: ceph-msgr ceph_con_workfn [libceph] >>>>> <4>[16097.962188] Call Trace: >>>>> <4>[16097.962353] ? __schedule+0x276/0x6e0 >>>>> <4>[16097.962359] ? schedule+0x40/0xb0 >>>>> <4>[16097.962364] ? schedule_preempt_disabled+0xa/0x10 >>>>> <4>[16097.962368] ? __mutex_lock.isra.8+0x2b5/0x4a0 >>>>> <4>[16097.962460] ? kick_requests+0x21/0x100 [ceph] >>>>> <4>[16097.962485] ? ceph_mdsc_handle_mdsmap+0x19c/0x5f0 [ceph] >>>>> <4>[16097.962503] ? extra_mon_dispatch+0x34/0x40 [ceph] >>>>> <4>[16097.962523] ? extra_mon_dispatch+0x34/0x40 [ceph] >>>>> <4>[16097.962580] ? dispatch+0x77/0x930 [libceph] >>>>> <4>[16097.962602] ? try_read+0x78b/0x11e0 [libceph] >>>>> <4>[16097.962619] ? __switch_to_asm+0x40/0x70 >>>>> <4>[16097.962623] ? __switch_to_asm+0x34/0x70 >>>>> <4>[16097.962627] ? __switch_to_asm+0x40/0x70 >>>>> <4>[16097.962631] ? __switch_to_asm+0x34/0x70 >>>>> <4>[16097.962635] ? __switch_to_asm+0x40/0x70 >>>>> <4>[16097.962654] ? ceph_con_workfn+0x130/0x5e0 [libceph] >>>>> <4>[16097.962713] ? process_one_work+0x1ad/0x370 >>>>> <4>[16097.962717] ? worker_thread+0x30/0x390 >>>>> <4>[16097.962722] ? create_worker+0x1a0/0x1a0 >>>>> <4>[16097.962737] ? kthread+0x112/0x130 >>>>> <4>[16097.962742] ? kthread_park+0x80/0x80 >>>>> <4>[16097.962747] ? ret_from_fork+0x35/0x40 >>>>> <3>[16097.962758] INFO: task kworker/25:1:1747 blocked for more than 122 seconds. >>>>> <3>[16097.963233] Tainted: G E 5.7.0-rc5+ #80 >>>>> <3>[16097.963792] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. >>>>> <6>[16097.964298] kworker/25:1 D 0 1747 2 0x80004080 >>>>> <6>[16097.964325] Workqueue: ceph-msgr ceph_con_workfn [libceph] >>>>> <4>[16097.964331] Call Trace: >>>>> <4>[16097.964340] ? __schedule+0x276/0x6e0 >>>>> <4>[16097.964344] ? schedule+0x40/0xb0 >>>>> <4>[16097.964347] ? schedule_preempt_disabled+0xa/0x10 >>>>> <4>[16097.964351] ? __mutex_lock.isra.8+0x2b5/0x4a0 >>>>> <4>[16097.964376] ? handle_reply+0x33f/0x6f0 [ceph] >>>>> <4>[16097.964407] ? dispatch+0xa6/0xbc0 [ceph] >>>>> <4>[16097.964429] ? read_partial_message+0x214/0x770 [libceph] >>>>> <4>[16097.964449] ? try_read+0x78b/0x11e0 [libceph] >>>>> <4>[16097.964454] ? __switch_to_asm+0x40/0x70 >>>>> <4>[16097.964458] ? __switch_to_asm+0x34/0x70 >>>>> <4>[16097.964461] ? __switch_to_asm+0x40/0x70 >>>>> <4>[16097.964465] ? __switch_to_asm+0x34/0x70 >>>>> <4>[16097.964470] ? __switch_to_asm+0x40/0x70 >>>>> <4>[16097.964489] ? ceph_con_workfn+0x130/0x5e0 [libceph] >>>>> <4>[16097.964494] ? process_one_work+0x1ad/0x370 >>>>> <4>[16097.964498] ? worker_thread+0x30/0x390 >>>>> <4>[16097.964501] ? create_worker+0x1a0/0x1a0 >>>>> <4>[16097.964506] ? kthread+0x112/0x130 >>>>> <4>[16097.964511] ? kthread_park+0x80/0x80 >>>>> <4>[16097.964516] ? ret_from_fork+0x35/0x40 >>>>> >>>>> URL: https://tracker.ceph.com/issues/45609 >>>>> Reported-by: "Yan, Zheng" >>>>> Signed-off-by: Xiubo Li >>>>> --- >>>>> fs/ceph/mds_client.c | 4 ++-- >>>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c >>>>> index 6c283c5..0e0ab01 100644 >>>>> --- a/fs/ceph/mds_client.c >>>>> +++ b/fs/ceph/mds_client.c >>>>> @@ -3769,8 +3769,6 @@ static int encode_snap_realms(struct ceph_mds_client *mdsc, >>>>> * recovering MDS might have. >>>>> * >>>>> * This is a relatively heavyweight operation, but it's rare. >>>>> - * >>>>> - * called with mdsc->mutex held. >>>>> */ >>>>> static void send_mds_reconnect(struct ceph_mds_client *mdsc, >>>>> struct ceph_mds_session *session) >>>>> @@ -4024,7 +4022,9 @@ static void check_new_map(struct ceph_mds_client *mdsc, >>>>> oldstate != CEPH_MDS_STATE_STARTING) >>>>> pr_info("mds%d recovery completed\n", s->s_mds); >>>>> kick_requests(mdsc, i); >>>>> + mutex_unlock(&mdsc->mutex); >>>>> mutex_lock(&s->s_mutex); >>>>> + mutex_lock(&mdsc->mutex); >>>>> ceph_kick_flushing_caps(mdsc, s); >>>>> mutex_unlock(&s->s_mutex); >>>>> wake_up_session_caps(s, RECONNECT); >>>> Good catch. Merged into testing branch. >>> These stack traces take up the entire screen and provide very >>> little information. Since this is a simple lock ordering issue, >>> could they be replaced with a short description and perhaps a >>> reference to mds_client.h where lock dependencies are documented? >> Hmm, it makes sense. >> >> Should I post a V2 ? Or will Jeff do the fix on the testing branch ? >> > I went ahead and just fixed it in the testing branch. Let me know if you want to revise the verbiage. > That looks good to me. Thanks Jeff. BRs Xiubo