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 6B723C433EF for ; Fri, 22 Jul 2022 13:43:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230089AbiGVNn0 (ORCPT ); Fri, 22 Jul 2022 09:43:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52714 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229441AbiGVNnZ (ORCPT ); Fri, 22 Jul 2022 09:43:25 -0400 Received: from out0.migadu.com (out0.migadu.com [94.23.1.103]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 477CE13E36 for ; Fri, 22 Jul 2022 06:43:21 -0700 (PDT) Message-ID: <921120a1-28fa-dd2a-b6fc-227faa3c8ace@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1658497399; 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=IMl81u3/E6xVxNZ9UVoU10FqjJdUG9J/XQjXB4f/g3g=; b=JuiC5ADGrGlGVjfLYK1NAMe/RsYJBphh/J+iWzBffh+DVPlU+CO+U9IVCmPJUHdAfbs1cr 6znwfmKbbJpdzg95Ac/f7rpKB9bYfjnZy1CQcSdih3GEgYIQVdvqMEimHjUpSf4c9wX+R6 zVDOR4L3LHTzDZ47Jbj6CfB0DgnNHEE= Date: Fri, 22 Jul 2022 21:43:05 +0800 MIME-Version: 1.0 Subject: Re: [PATCHv6 1/4] RDMA/rxe: Fix dead lock caused by __rxe_add_to_pool interrupted by rxe_pool_get_index To: "yangx.jy@fujitsu.com" , "jgg@ziepe.ca" , "leon@kernel.org" , "linux-rdma@vger.kernel.org" , "rpearsonhpe@gmail.com" Cc: Yi Zhang References: <20220422194416.983549-1-yanjun.zhu@linux.dev> <5c2c8590-4798-ab70-2a15-949ca245ddae@fujitsu.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yanjun Zhu In-Reply-To: <5c2c8590-4798-ab70-2a15-949ca245ddae@fujitsu.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 2022/7/22 14:51, yangx.jy@fujitsu.com 写道: > Hi Yanjun, Bob > > Could you tell me if the dead lock issue has been fixed by the following > issue: > [PATCH v16 2/2] RDMA/rxe: Convert read side locking to rcu Hi， Xiao Normally I applied this "RDMA/rxe: Fix dead lock caused by __rxe_add_to_pool interrupted by rxe_pool_get_index" patch series to fix this problem. And I am not sure if this problem is fixed by "[PATCH v16 2/2] RDMA/rxe: Convert read side locking to rcu". Zhu Yanjun > > Best Regards, > Xiao Yang > > On 2022/4/23 3:44, yanjun.zhu@linux.dev 写道: >> From: Zhu Yanjun >> >> This is a dead lock problem. >> The ah_pool 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] >> >> Then ah_pool 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] >> >> >> 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. >> >> CPU0 >> ---- >> lock(&xa->xa_lock#15); <----- __rxe_add_to_pool >> >> lock(&xa->xa_lock#15); <---- rxe_pool_get_index >> >> *** DEADLOCK *** >> >> Fixes: 3225717f6dfa ("RDMA/rxe: Replace red-black trees by carrays") >> Reported-and-tested-by: Yi Zhang >> Signed-off-by: Zhu Yanjun >> --- >> V5->V6: One dead lock fix in one commit >> V4->V5: Commit logs are changed. >> 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 | 11 +++++++---- >> 1 file changed, 7 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/infiniband/sw/rxe/rxe_pool.c b/drivers/infiniband/sw/rxe/rxe_pool.c >> index 87066d04ed18..67f1d4733682 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; >> } >> @@ -155,6 +155,7 @@ 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 +167,10 @@ 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; >> >> @@ -201,7 +204,7 @@ 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; >> >> - xa_erase(&pool->xa, elem->index); >> + xa_erase_irq(&pool->xa, elem->index); >> >> if (pool->cleanup) >> pool->cleanup(elem);