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Tue, 11 Jan 2022 08:23:06 +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 08:23:06 +0000 (GMT) Message-ID: <8b720956-c8fe-0fe2-b019-70518d5c60c8@linux.ibm.com> Date: Tue, 11 Jan 2022 09:23:08 +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 1/3] net/smc: Resolve the race between link group access and termination 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> <1641806784-93141-2-git-send-email-guwen@linux.alibaba.com> From: Karsten Graul Organization: IBM Deutschland Research & Development GmbH In-Reply-To: <1641806784-93141-2-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-GUID: 3-XXLShBQ0Q4E7NQgLXScZgiyhhOrOrK X-Proofpoint-ORIG-GUID: oMbR3VimQlmhhihOmexF_qD8Y4fVweVl 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 spamscore=0 impostorscore=0 mlxscore=0 adultscore=0 clxscore=1015 mlxlogscore=999 lowpriorityscore=0 priorityscore=1501 suspectscore=0 phishscore=0 bulkscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2201110044 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/01/2022 10:26, Wen Gu wrote: > We encountered some crashes caused by the race between the access > and the termination of link groups. > > > +/* won't be freed until no one accesses to lgr anymore */ > +static void __smc_lgr_free(struct smc_link_group *lgr) > +{ > + smc_lgr_free_bufs(lgr); > + if (!lgr->is_smcd) > + smc_wr_free_lgr_mem(lgr); > + kfree(lgr); > +} > + > /* remove a link group */ > static void smc_lgr_free(struct smc_link_group *lgr) > { > @@ -1298,7 +1326,6 @@ static void smc_lgr_free(struct smc_link_group *lgr) > smc_llc_lgr_clear(lgr); > } > > - smc_lgr_free_bufs(lgr); > destroy_workqueue(lgr->tx_wq); > if (lgr->is_smcd) { > smc_ism_put_vlan(lgr->smcd, lgr->vlan_id); > @@ -1306,11 +1333,21 @@ static void smc_lgr_free(struct smc_link_group *lgr) > if (!atomic_dec_return(&lgr->smcd->lgr_cnt)) > wake_up(&lgr->smcd->lgrs_deleted); > } else { > - smc_wr_free_lgr_mem(lgr); > if (!atomic_dec_return(&lgr_cnt)) > wake_up(&lgrs_deleted); These waiters (seaparate ones for smcd and smcr) are used to wait for all lgrs to be deleted when a module unload or reboot was triggered, so it must only be woken up when the lgr is actually freed.