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 C48F0C433EF for ; Fri, 15 Apr 2022 06:49:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239658AbiDOGwY (ORCPT ); Fri, 15 Apr 2022 02:52:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38072 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237495AbiDOGwX (ORCPT ); Fri, 15 Apr 2022 02:52:23 -0400 Received: from out1.migadu.com (out1.migadu.com [91.121.223.63]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC541B3691 for ; Thu, 14 Apr 2022 23:49:53 -0700 (PDT) Message-ID: <5597e6eb-1543-6895-77fc-426e0a601338@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1650005392; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IH4KfqLgHtzqb7J2hQTZH4KBE4whnVp5hEG5umIqiW0=; b=dZzPlff/T5ENzyNKiJmfXvh6Fhimombl1Fh5QJgG7quNHnEUIR9CvQoxNXAbC/CUhFHaGE hYZ08IypHUjc5sSZzhokbzuWiqepJvsPVmn57LcgA7sdb3g5b2xUZlZOrHsybiJWmCEpbS dUtFsTA7fNb5cWiFRl2mlnLB/8fk3rM= Date: Fri, 15 Apr 2022 14:49:48 +0800 MIME-Version: 1.0 Subject: Re: [PATCHv4 1/2] RDMA/rxe: Fix a dead lock problem To: Bob Pearson , Yanjun Zhu , jgg@ziepe.ca, leon@kernel.org, linux-rdma@vger.kernel.org References: <20220415195630.279510-1-yanjun.zhu@linux.dev> <0d88246e-c29a-27c0-95c5-da73f52e6a59@linux.dev> <726e75b0-c165-92f8-c367-1a5a777bc8b1@gmail.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yanjun Zhu In-Reply-To: <726e75b0-c165-92f8-c367-1a5a777bc8b1@gmail.com> 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 2022/4/15 14:35, Bob Pearson 写道: > On 4/15/22 00:54, Yanjun Zhu wrote: >> >> 在 2022/4/15 13:37, Bob Pearson 写道: >>> On 4/15/22 14:56, 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 >>> There is a separate xarray for each object pool. So this one is >>> rxe->pd_pool.xa.xa_lock from rxe_alloc_pd(). >>> >>>> 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 >>> And this one is rxe->ah_pool.xa.xa_lock from rxe_requester >>> in the process of sending a UD packet from a work request >>> which contains the index of the ah. >>> >>> For your story to work there needs to be an another ah_pool.xa.xa_lock somewhere. >>> Let's assume it is there somewhere and it's from (a different) add_to_pool call >>> then the add_to_pool_ routine should disable interrupts when it gets the lock >>> with spin_lock_xxx. But only for AH objects. >>> >>> This may be old news. >> >> What do you mean? Please check the call trace in the bug. > > I mean the trace you show here shows an instance of xa_lock being > acquired from the pd pool followed by an instance of xa_lock being > acquired from rxe_pool_get_index from the ah pool. They are different > locks. They can't deadlock against each other. So there must be > some other trace (not shown) that also gets xa_lock from the ah pool. Please check the bug report mail. The link is news://nntp.lore.kernel.org:119/CAHj4cs-MT13RiEsWXUAcX_H5jEtjsebuZgSeUcfptNVuELgjYQ@mail.gmail.com BTW, what is the update about wr crash caused by your xarray patches? Zhu Yanjun > >> >> Zhu Yanjun >> >>> >>>>   >>>> >>>>  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 >>>> --- >>>> V3->V4: xa_lock_irq locks are used. >>>> 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 | 20 ++++++++++++++------ >>>>   1 file changed, 14 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/drivers/infiniband/sw/rxe/rxe_pool.c b/drivers/infiniband/sw/rxe/rxe_pool.c >>>> index 87066d04ed18..f1f06dc7e64f 100644 >>>> --- a/drivers/infiniband/sw/rxe/rxe_pool.c >>>> +++ b/drivers/infiniband/sw/rxe/rxe_pool.c >>>> @@ -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_ALLOC | XA_FLAGS_LOCK_IRQ); >>>>       pool->limit.min = info->min_index; >>>>       pool->limit.max = info->max_index; >>>>   } >>>> @@ -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_irq(&pool->xa); >>>> +    err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit, >>>> +                &pool->next, GFP_KERNEL); >>>> +    xa_unlock_irq(&pool->xa); >>>>       if (err) >>>>           goto err_free; >>>>   @@ -155,6 +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; >>>> @@ -166,8 +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); >>>>   -    err = xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit, >>>> -                  &pool->next, GFP_KERNEL); >>>> +    xa_lock_irqsave(&pool->xa, flags); >>>> +    err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit, >>>> +                &pool->next, GFP_ATOMIC); >>>> +    xa_unlock_irqrestore(&pool->xa, flags); >>>>       if (err) >>>>           goto err_cnt; >>>>   @@ -200,8 +205,11 @@ static void rxe_elem_release(struct kref *kref) >>>>   { >>>>       struct rxe_pool_elem *elem = container_of(kref, typeof(*elem), ref_cnt); >>>>       struct rxe_pool *pool = elem->pool; >>>> +    unsigned long flags; >>>>   -    xa_erase(&pool->xa, elem->index); >>>> +    xa_lock_irqsave(&pool->xa, flags); >>>> +    __xa_erase(&pool->xa, elem->index); >>>> +    xa_unlock_irqrestore(&pool->xa, flags); >>>>         if (pool->cleanup) >>>>           pool->cleanup(elem); >