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 7030CC433EF for ; Thu, 14 Apr 2022 13:01:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235554AbiDNNEI (ORCPT ); Thu, 14 Apr 2022 09:04:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58126 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241778AbiDNNEH (ORCPT ); Thu, 14 Apr 2022 09:04:07 -0400 Received: from out1.migadu.com (out1.migadu.com [IPv6:2001:41d0:2:863f::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F9D68EB67 for ; Thu, 14 Apr 2022 06:01:41 -0700 (PDT) Message-ID: <56c4e893-223d-ad6b-2fa9-ca8b2aace9de@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1649941299; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NJNvl5mEXOQ+io0aiwdVugIvdlNqEV/70QIq0LTjbfc=; b=lSuW0UINozwOoG621m7iosqQlB47Zm9yurctNfoqxoM1Kua+vUpQtvw67Y153VN41a+snX IlEwlmqgr5IGZvbOsd1XKiXt31bZ05ZTRHAkpD0H/O+mb4qGTQcPOBra1Zs1gLCCik8ZgE WCtpXpEUEz9eylz26Dmlm4fBeziQjp0= Date: Thu, 14 Apr 2022 21:01:29 +0800 MIME-Version: 1.0 Subject: Re: [PATCHv3 1/1] RDMA/rxe: Fix a dead lock problem X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yanjun Zhu To: Jason Gunthorpe Cc: leon@kernel.org, linux-rdma@vger.kernel.org, Yi Zhang References: <20220413074208.1401112-1-yanjun.zhu@linux.dev> <20220413004504.GH64706@ziepe.ca> <81db8dcc-e417-bff5-b7ec-1067c717ea62@linux.dev> In-Reply-To: <81db8dcc-e417-bff5-b7ec-1067c717ea62@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org 在 2022/4/13 22:50, Yanjun Zhu 写道: > > 在 2022/4/13 8:45, Jason Gunthorpe 写道: >> On Wed, Apr 13, 2022 at 03:42:08AM -0400, yanjun.zhu@linux.dev wrote: >>> From: Zhu Yanjun >>> >>> This is a dead lock problem. >>> The xa_lock first is acquired in this: >>> >>> {SOFTIRQ-ON-W} state was registered at: >>> >>>    lock_acquire+0x1d2/0x5a0 >>>    _raw_spin_lock+0x33/0x80 >>>    __rxe_add_to_pool+0x183/0x230 [rdma_rxe] >>>    __ib_alloc_pd+0xf9/0x550 [ib_core] >>>    ib_mad_init_device+0x2d9/0xd20 [ib_core] >>>    add_client_context+0x2fa/0x450 [ib_core] >>>    enable_device_and_get+0x1b7/0x350 [ib_core] >>>    ib_register_device+0x757/0xaf0 [ib_core] >>>    rxe_register_device+0x2eb/0x390 [rdma_rxe] >>>    rxe_net_add+0x83/0xc0 [rdma_rxe] >>>    rxe_newlink+0x76/0x90 [rdma_rxe] >>>    nldev_newlink+0x245/0x3e0 [ib_core] >>>    rdma_nl_rcv_msg+0x2d4/0x790 [ib_core] >>>    rdma_nl_rcv+0x1ca/0x3f0 [ib_core] >>>    netlink_unicast+0x43b/0x640 >>>    netlink_sendmsg+0x7eb/0xc40 >>>    sock_sendmsg+0xe0/0x110 >>>    __sys_sendto+0x1d7/0x2b0 >>>    __x64_sys_sendto+0xdd/0x1b0 >>>    do_syscall_64+0x37/0x80 >>>    entry_SYSCALL_64_after_hwframe+0x44/0xae >>> >>> Then xa_lock is acquired in this: >>> >>> {IN-SOFTIRQ-W}: >>> >>> Call Trace: >>>   >>>    dump_stack_lvl+0x44/0x57 >>>    mark_lock.part.52.cold.79+0x3c/0x46 >>>    __lock_acquire+0x1565/0x34a0 >>>    lock_acquire+0x1d2/0x5a0 >>>    _raw_spin_lock_irqsave+0x42/0x90 >>>    rxe_pool_get_index+0x72/0x1d0 [rdma_rxe] >>>    rxe_get_av+0x168/0x2a0 [rdma_rxe] >>>    rxe_requester+0x75b/0x4a90 [rdma_rxe] >>>    rxe_do_task+0x134/0x230 [rdma_rxe] >>>    tasklet_action_common.isra.12+0x1f7/0x2d0 >>>    __do_softirq+0x1ea/0xa4c >>>    run_ksoftirqd+0x32/0x60 >>>    smpboot_thread_fn+0x503/0x860 >>>    kthread+0x29b/0x340 >>>    ret_from_fork+0x1f/0x30 >>>   >>> >>>  From the above, in the function __rxe_add_to_pool, >>> xa_lock is acquired. Then the function __rxe_add_to_pool >>> is interrupted by softirq. The function >>> rxe_pool_get_index will also acquire xa_lock. >>> >>> Finally, the dead lock appears. >>> >>> [  296.806097]        CPU0 >>> [  296.808550]        ---- >>> [  296.811003]   lock(&xa->xa_lock#15);  <----- __rxe_add_to_pool >>> [  296.814583]   >>> [  296.817209]     lock(&xa->xa_lock#15); <---- rxe_pool_get_index >>> [  296.820961] >>>                   *** DEADLOCK *** >>> >>> Fixes: 3225717f6dfa ("RDMA/rxe: Replace red-black trees by carrays") >>> Reported-and-tested-by: Yi Zhang >>> Signed-off-by: Zhu Yanjun >>> --- >>> V2->V3: __rxe_add_to_pool is between spin_lock and spin_unlock, so >>>          GFP_ATOMIC is used in __rxe_add_to_pool. >>> V1->V2: Replace GFP_KERNEL with GFP_ATOMIC >>> --- >>>   drivers/infiniband/sw/rxe/rxe_pool.c | 17 ++++++++++++----- >>>   1 file changed, 12 insertions(+), 5 deletions(-) >>> >>> diff --git a/drivers/infiniband/sw/rxe/rxe_pool.c >>> b/drivers/infiniband/sw/rxe/rxe_pool.c >>> index 87066d04ed18..b9b147df4020 100644 >>> --- a/drivers/infiniband/sw/rxe/rxe_pool.c >>> +++ b/drivers/infiniband/sw/rxe/rxe_pool.c >>> @@ -138,8 +138,10 @@ void *rxe_alloc(struct rxe_pool *pool) >>>       elem->obj = obj; >>>       kref_init(&elem->ref_cnt); >>> -    err = xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit, >>> -                  &pool->next, GFP_KERNEL); >>> +    xa_lock_bh(&pool->xa); >>> +    err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit, >>> +                &pool->next, GFP_KERNEL); >>> +    xa_unlock_bh(&pool->xa); >>>       if (err) >>>           goto err_free; >> You can't mix bh and not bh locks, either this is an irq spinlock or >> it is bh spinlock, pick one and also ensure that the proper xa_init >> flag is set. > > Got it. I should use irq spinlock. So XA_FLAGS_LOCK_IRQ is added in > xa_init flags. > > So the code should be: > > @@ -106,7 +106,7 @@ void rxe_pool_init(struct rxe_dev *rxe, struct > rxe_pool *pool, > >         atomic_set(&pool->num_elem, 0); > > -       xa_init_flags(&pool->xa, XA_FLAGS_ALLOC); > +       xa_init_flags(&pool->xa, XA_FLAGS_LOCK_IRQ | XA_FLAGS_ALLOC); >         pool->limit.min = info->min_index; >         pool->limit.max = info->max_index; >  } > @@ -138,10 +138,10 @@ void *rxe_alloc(struct rxe_pool *pool) >         elem->obj = obj; >         kref_init(&elem->ref_cnt); > > -       xa_lock_bh(&pool->xa); > +       xa_lock_irq(&pool->xa); >         err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, > pool->limit, >                                 &pool->next, GFP_KERNEL); > -       xa_unlock_bh(&pool->xa); > +       xa_unlock_irq(&pool->xa); >         if (err) >                 goto err_free; > >> >>> @@ -166,8 +168,10 @@ int __rxe_add_to_pool(struct rxe_pool *pool, >>> struct rxe_pool_elem *elem) >>>       elem->obj = (u8 *)elem - pool->elem_offset; >>>       kref_init(&elem->ref_cnt); >>> -    err = xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit, >>> -                  &pool->next, GFP_KERNEL); >>> +    xa_lock_irq(&pool->xa); >>> +    err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit, >>> +                &pool->next, GFP_ATOMIC); >>> +    xa_unlock_irq(&pool->xa); >>>       if (err) >>>           goto err_cnt; >> Still no, this does almost every allocation - only AH with the >> non-blocking flag set should use this path. > > Yes. Got it. > > In the following, xa_lock_irqsave/xa_unlock_irqrestore should be used. > > int ib_send_cm_req(struct ib_cm_id *cm_id, > >                    struct ib_cm_req_param *param) > { > > ... > > spin_lock_irqsave(&cm_id_priv->lock, flags); > > ... > > __rxe_add_to_pool > > ... > > spin_unlock_irqrestore(&cm_id_priv->lock, flags); Hi，Jason To the function ib_send_cm_req, the call chain is as below. ib_send_cm_req --> cm_alloc_priv_msg --> cm_alloc_msg --> rdma_create_ah --> _rdma_create_ah --> rxe_create_ah --> rxe_av_chk_attr -->__rxe_add_to_pool As such, xa_lock_irqsave/irqrestore is selected. Zhu Yanjun > > > So the diff is as below: > > @@ -157,6 +157,7 @@ void *rxe_alloc(struct rxe_pool *pool) >  int __rxe_add_to_pool(struct rxe_pool *pool, struct rxe_pool_elem *elem) >  { >         int err; > +       unsigned long flags; > >         if (WARN_ON(pool->flags & RXE_POOL_ALLOC)) >                 return -EINVAL; > @@ -168,10 +169,10 @@ int __rxe_add_to_pool(struct rxe_pool *pool, > struct rxe_pool_elem *elem) >         elem->obj = (u8 *)elem - pool->elem_offset; >         kref_init(&elem->ref_cnt); > > -       xa_lock_irq(&pool->xa); > +       xa_lock_irqsave(&pool->xa, flags); >         err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, > pool->limit, >                                 &pool->next, GFP_ATOMIC); > -       xa_unlock_irq(&pool->xa); > +       xa_unlock_irqrestore(&pool->xa, flags); >         if (err) >                 goto err_cnt; > > Please comment. Thanks a lot. > > Zhu Yanjun > >> >> Jason