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Tue, 11 Jan 2022 08:40:03 +0000 (GMT) Received: from [9.145.30.70] (unknown [9.145.30.70]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 11 Jan 2022 08:40:03 +0000 (GMT) Message-ID: <8f13aa62-6360-8038-3041-86fd51b40a3e@linux.ibm.com> Date: Tue, 11 Jan 2022 09:40:05 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.4.1 Subject: Re: [PATCH net 3/3] net/smc: Resolve the race between SMC-R link access and clear Content-Language: en-US To: Wen Gu , davem@davemloft.net, kuba@kernel.org Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <1641806784-93141-1-git-send-email-guwen@linux.alibaba.com> <1641806784-93141-4-git-send-email-guwen@linux.alibaba.com> From: Karsten Graul Organization: IBM Deutschland Research & Development GmbH In-Reply-To: <1641806784-93141-4-git-send-email-guwen@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: NXEx7vB3J0fDkHsJfkpbQ9vQ6QwtIsh8 X-Proofpoint-GUID: txm97WcY5lQDdZP_ZS2oA1DJ7DeY2gqH X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-01-11_03,2022-01-10_02,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 mlxlogscore=999 spamscore=0 suspectscore=0 phishscore=0 adultscore=0 clxscore=1015 mlxscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2201110047 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/01/2022 10:26, Wen Gu wrote: > @@ -1226,15 +1245,23 @@ void smcr_link_clear(struct smc_link *lnk, bool log) > smc_wr_free_link(lnk); > smc_ib_destroy_queue_pair(lnk); > smc_ib_dealloc_protection_domain(lnk); > - smc_wr_free_link_mem(lnk); > - smc_lgr_put(lnk->lgr); /* lgr_hold in smcr_link_init() */ > smc_ibdev_cnt_dec(lnk); > put_device(&lnk->smcibdev->ibdev->dev); > smcibdev = lnk->smcibdev; > - memset(lnk, 0, sizeof(struct smc_link)); > - lnk->state = SMC_LNK_UNUSED; > if (!atomic_dec_return(&smcibdev->lnk_cnt)) > wake_up(&smcibdev->lnks_deleted); Same here, waiter should not be woken up until the link memory is actually freed. > + smcr_link_put(lnk); /* theoretically last link_put */ > +} > + > +void smcr_link_hold(struct smc_link *lnk) > +{ > + refcount_inc(&lnk->refcnt); > +} > + > +void smcr_link_put(struct smc_link *lnk) > +{ > + if (refcount_dec_and_test(&lnk->refcnt)) > + __smcr_link_clear(lnk); > }