From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC800C433EF for ; Sat, 15 Jan 2022 10:29:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232855AbiAOK3u (ORCPT ); Sat, 15 Jan 2022 05:29:50 -0500 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:53810 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229530AbiAOK3u (ORCPT ); Sat, 15 Jan 2022 05:29:50 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R211e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=dust.li@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0V1si10H_1642242587; Received: from localhost(mailfrom:dust.li@linux.alibaba.com fp:SMTPD_---0V1si10H_1642242587) by smtp.aliyun-inc.com(127.0.0.1); Sat, 15 Jan 2022 18:29:48 +0800 Date: Sat, 15 Jan 2022 18:29:47 +0800 From: "dust.li" To: Wen Gu , kgraul@linux.ibm.com, davem@davemloft.net, kuba@kernel.org Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net] net/smc: Fix hung_task when removing SMC-R devices Message-ID: <20220115102947.GB13341@linux.alibaba.com> Reply-To: dust.li@linux.alibaba.com References: <1642167444-107744-1-git-send-email-guwen@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1642167444-107744-1-git-send-email-guwen@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On Fri, Jan 14, 2022 at 09:37:24PM +0800, Wen Gu wrote: >A hung_task is observed when removing SMC-R devices. Suppose that >a link group has two active links(lnk_A, lnk_B) associated with two >different SMC-R devices(dev_A, dev_B). When dev_A is removed, the >link group will be removed from smc_lgr_list and added into >lgr_linkdown_list. lnk_A will be cleared and smcibdev(A)->lnk_cnt >will reach to zero. However, when dev_B is removed then, the link >group can't be found in smc_lgr_list and lnk_B won't be cleared, >making smcibdev->lnk_cnt never reaches zero, which causes a hung_task. > >This patch fixes this issue by restoring the implementation of >smc_smcr_terminate_all() to what it was before commit 349d43127dac >("net/smc: fix kernel panic caused by race of smc_sock"). The original >implementation also satisfies the intention that make sure QP destroy >earlier than CQ destroy because we will always wait for smcibdev->lnk_cnt >reaches zero, which guarantees QP has been destroyed. Good catch, thank you ! Update the comments of smc_smcr_terminate_all as well ? > >Fixes: 349d43127dac ("net/smc: fix kernel panic caused by race of smc_sock") >Signed-off-by: Wen Gu Reviewed-by: Dust Li >--- > net/smc/smc_core.c | 13 +------------ > 1 file changed, 1 insertion(+), 12 deletions(-) > >diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c >index b19c0aa..1124594 100644 >--- a/net/smc/smc_core.c >+++ b/net/smc/smc_core.c >@@ -1533,7 +1533,6 @@ void smc_smcr_terminate_all(struct smc_ib_device *smcibdev) > { > struct smc_link_group *lgr, *lg; > LIST_HEAD(lgr_free_list); >- LIST_HEAD(lgr_linkdown_list); > int i; > > spin_lock_bh(&smc_lgr_list.lock); >@@ -1545,7 +1544,7 @@ void smc_smcr_terminate_all(struct smc_ib_device *smcibdev) > list_for_each_entry_safe(lgr, lg, &smc_lgr_list.list, list) { > for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) { > if (lgr->lnk[i].smcibdev == smcibdev) >- list_move_tail(&lgr->list, &lgr_linkdown_list); >+ smcr_link_down_cond_sched(&lgr->lnk[i]); > } > } > } >@@ -1557,16 +1556,6 @@ void smc_smcr_terminate_all(struct smc_ib_device *smcibdev) > __smc_lgr_terminate(lgr, false); > } > >- list_for_each_entry_safe(lgr, lg, &lgr_linkdown_list, list) { >- for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) { >- if (lgr->lnk[i].smcibdev == smcibdev) { >- mutex_lock(&lgr->llc_conf_mutex); >- smcr_link_down_cond(&lgr->lnk[i]); >- mutex_unlock(&lgr->llc_conf_mutex); >- } >- } >- } >- > if (smcibdev) { > if (atomic_read(&smcibdev->lnk_cnt)) > wait_event(smcibdev->lnks_deleted, >-- >1.8.3.1