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 02D4CECAAD4 for ; Tue, 30 Aug 2022 14:15:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230240AbiH3OPj (ORCPT ); Tue, 30 Aug 2022 10:15:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55628 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229800AbiH3OPj (ORCPT ); Tue, 30 Aug 2022 10:15:39 -0400 Received: from out30-57.freemail.mail.aliyun.com (out30-57.freemail.mail.aliyun.com [115.124.30.57]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9D50B5A89D; Tue, 30 Aug 2022 07:15:34 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R481e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046051;MF=tonylu@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0VNlVrHu_1661868930; Received: from localhost(mailfrom:tonylu@linux.alibaba.com fp:SMTPD_---0VNlVrHu_1661868930) by smtp.aliyun-inc.com; Tue, 30 Aug 2022 22:15:30 +0800 Date: Tue, 30 Aug 2022 22:15:29 +0800 From: Tony Lu To: liuyacan@corp.netease.com Cc: davem@davemloft.net, edumazet@google.com, kgraul@linux.ibm.com, kuba@kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, wenjia@linux.ibm.com Subject: Re: [PATCH net v2] net/smc: fix listen processing for SMC-Rv2 Message-ID: Reply-To: Tony Lu References: <20220830030555.373860-1-liuyacan@corp.netease.com> <20220830055806.1142343-1-liuyacan@corp.netease.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220830055806.1142343-1-liuyacan@corp.netease.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Aug 30, 2022 at 01:58:06PM +0800, liuyacan@corp.netease.com wrote: > > > From: liuyacan > > > > > > After modifying the QP to the Error state, all RX WR would be > > > completed with WC in IB_WC_WR_FLUSH_ERR status. Current > > > implementation does not wait for it is done, but free the link > > > directly. So there is a risk that accessing the freed link in > > > tasklet context. > > > > > > Here is a crash example: > > > > > > BUG: unable to handle page fault for address: ffffffff8f220860 > > > #PF: supervisor write access in kernel mode > > > #PF: error_code(0x0002) - not-present page > > > PGD f7300e067 P4D f7300e067 PUD f7300f063 PMD 8c4e45063 PTE 800ffff08c9df060 > > > Oops: 0002 [#1] SMP PTI > > > CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: G S OE 5.10.0-0607+ #23 > > > Hardware name: Inspur NF5280M4/YZMB-00689-101, BIOS 4.1.20 07/09/2018 > > > RIP: 0010:native_queued_spin_lock_slowpath+0x176/0x1b0 > > > Code: f3 90 48 8b 32 48 85 f6 74 f6 eb d5 c1 ee 12 83 e0 03 83 ee 01 48 c1 e0 05 48 63 f6 48 05 00 c8 02 00 48 03 04 f5 00 09 98 8e <48> 89 10 8b 42 08 85 c0 75 09 f3 90 8b 42 08 85 c0 74 f7 48 8b 32 > > > RSP: 0018:ffffb3b6c001ebd8 EFLAGS: 00010086 > > > RAX: ffffffff8f220860 RBX: 0000000000000246 RCX: 0000000000080000 > > > RDX: ffff91db1f86c800 RSI: 000000000000173c RDI: ffff91db62bace00 > > > RBP: ffff91db62bacc00 R08: 0000000000000000 R09: c00000010000028b > > > R10: 0000000000055198 R11: ffffb3b6c001ea58 R12: ffff91db80e05010 > > > R13: 000000000000000a R14: 0000000000000006 R15: 0000000000000040 > > > FS: 0000000000000000(0000) GS:ffff91db1f840000(0000) knlGS:0000000000000000 > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > CR2: ffffffff8f220860 CR3: 00000001f9580004 CR4: 00000000003706e0 > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > > Call Trace: > > > > > > _raw_spin_lock_irqsave+0x30/0x40 > > > mlx5_ib_poll_cq+0x4c/0xc50 [mlx5_ib] > > > smc_wr_rx_tasklet_fn+0x56/0xa0 [smc] > > > tasklet_action_common.isra.21+0x66/0x100 > > > __do_softirq+0xd5/0x29c > > > asm_call_irq_on_stack+0x12/0x20 > > > > > > do_softirq_own_stack+0x37/0x40 > > > irq_exit_rcu+0x9d/0xa0 > > > sysvec_call_function_single+0x34/0x80 > > > asm_sysvec_call_function_single+0x12/0x20 > > > > > > Signed-off-by: liuyacan > > > --- > > > net/smc/smc_core.c | 2 ++ > > > net/smc/smc_core.h | 2 ++ > > > net/smc/smc_wr.c | 12 ++++++++++++ > > > net/smc/smc_wr.h | 3 +++ > > > 4 files changed, 19 insertions(+) > > > > > > diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c > > > index ff49a11f5..b632a33f1 100644 > > > --- a/net/smc/smc_core.c > > > +++ b/net/smc/smc_core.c > > > @@ -752,6 +752,7 @@ int smcr_link_init(struct smc_link_group *lgr, struct smc_link *lnk, > > > atomic_inc(&lnk->smcibdev->lnk_cnt); > > > refcount_set(&lnk->refcnt, 1); /* link refcnt is set to 1 */ > > > lnk->clearing = 0; > > > + lnk->rx_drained = 0; > > > lnk->path_mtu = lnk->smcibdev->pattr[lnk->ibport - 1].active_mtu; > > > lnk->link_id = smcr_next_link_id(lgr); > > > lnk->lgr = lgr; > > > @@ -1269,6 +1270,7 @@ void smcr_link_clear(struct smc_link *lnk, bool log) > > > smcr_buf_unmap_lgr(lnk); > > > smcr_rtoken_clear_link(lnk); > > > smc_ib_modify_qp_error(lnk); > > > + smc_wr_drain_cq(lnk); > > > smc_wr_free_link(lnk); > > > smc_ib_destroy_queue_pair(lnk); > > > smc_ib_dealloc_protection_domain(lnk); > > > diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h > > > index fe8b524ad..0a469a3e7 100644 > > > --- a/net/smc/smc_core.h > > > +++ b/net/smc/smc_core.h > > > @@ -117,6 +117,7 @@ struct smc_link { > > > u64 wr_rx_id; /* seq # of last recv WR */ > > > u32 wr_rx_cnt; /* number of WR recv buffers */ > > > unsigned long wr_rx_tstamp; /* jiffies when last buf rx */ > > > + wait_queue_head_t wr_rx_drain_wait; /* wait for WR drain */ > > > > > > struct ib_reg_wr wr_reg; /* WR register memory region */ > > > wait_queue_head_t wr_reg_wait; /* wait for wr_reg result */ > > > @@ -138,6 +139,7 @@ struct smc_link { > > > u8 link_idx; /* index in lgr link array */ > > > u8 link_is_asym; /* is link asymmetric? */ > > > u8 clearing : 1; /* link is being cleared */ > > > + u8 rx_drained : 1; /* link is drained */ > > > refcount_t refcnt; /* link reference count */ > > > struct smc_link_group *lgr; /* parent link group */ > > > struct work_struct link_down_wrk; /* wrk to bring link down */ > > > diff --git a/net/smc/smc_wr.c b/net/smc/smc_wr.c > > > index 26f8f240d..f9992896a 100644 > > > --- a/net/smc/smc_wr.c > > > +++ b/net/smc/smc_wr.c > > > @@ -465,6 +465,10 @@ static inline void smc_wr_rx_process_cqes(struct ib_wc wc[], int num) > > > case IB_WC_RNR_RETRY_EXC_ERR: > > > case IB_WC_WR_FLUSH_ERR: > > > smcr_link_down_cond_sched(link); > > > + if (link->clearing && wc[i]->wr_id == link->wr_rx_id) { > > > + link->rx_drained = 1; > > > + wake_up(&link->wr_rx_drain_wait); > > > + } > > > > I am wondering if we should wait for all the wc comes back? > > I think yes, so other processes can safely destroy qp. > > > > > > break; > > > default: > > > smc_wr_rx_post(link); /* refill WR RX */ > > > @@ -631,6 +635,13 @@ static void smc_wr_init_sge(struct smc_link *lnk) > > > lnk->wr_reg.access = IB_ACCESS_LOCAL_WRITE | IB_ACCESS_REMOTE_WRITE; > > > } > > > > > > +void smc_wr_drain_cq(struct smc_link *lnk) > > > +{ > > > + wait_event_interruptible_timeout(lnk->wr_rx_drain_wait, > > > + (lnk->drained == 1), > > > + SMC_WR_RX_WAIT_DRAIN_TIME); > > > +} > > > > Should we wait for it with timeout? It should eventually be wake up > > normally before freeing link. Waiting for SMC_WR_RX_WAIT_DRAIN_TIME (2s) > > may also have this issue, although the probability of occurrence is > > greatly reduced. > > Indeed, there should logically probably be a perpetual wait here. I'm just worried if it > will get stuck for some unknown reason. IMHO, it's better to get stuck rather than to hide unknown issues. So I think timeout is unnecessary. Cheers, Tony Lu