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Wythe" , kgraul@linux.ibm.com, jaka@linux.ibm.com, wintera@linux.ibm.com Cc: kuba@kernel.org, davem@davemloft.net, netdev@vger.kernel.org, linux-s390@vger.kernel.org, linux-rdma@vger.kernel.org References: <1697009600-22367-1-git-send-email-alibuda@linux.alibaba.com> <1697009600-22367-6-git-send-email-alibuda@linux.alibaba.com> <305c7ae2-a902-3e30-5e67-b590d848d0ba@linux.alibaba.com> From: Wenjia Zhang In-Reply-To: <305c7ae2-a902-3e30-5e67-b590d848d0ba@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: C0quyvYEP4WhzEn6KStJRDVYT6ASe0AI X-Proofpoint-ORIG-GUID: vYMkW1jrXkGUBppO7mOHdx9bREvSSiN0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.980,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-10-19_16,2023-10-19_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 mlxscore=0 adultscore=0 impostorscore=0 lowpriorityscore=0 bulkscore=0 spamscore=0 priorityscore=1501 mlxlogscore=999 phishscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2309180000 definitions=main-2310190148 On 19.10.23 09:33, D. Wythe wrote: > > > On 10/19/23 4:26 AM, Wenjia Zhang wrote: >> >> >> On 17.10.23 04:06, D. Wythe wrote: >>> >>> >>> On 10/13/23 3:04 AM, Wenjia Zhang wrote: >>>> >>>> >>>> On 11.10.23 09:33, D. Wythe wrote: >>>>> From: "D. Wythe" >>>>> >>>>> Note that we always hold a reference to sock when attempting >>>>> to submit close_work. >>>> yes >>>> Therefore, if we have successfully >>>>> canceled close_work from pending, we MUST release that reference >>>>> to avoid potential leaks. >>>>> >>>> Isn't the corresponding reference already released inside the >>>> smc_close_passive_work()? >>>> >>> >>> Hi Wenjia, >>> >>> If we successfully cancel the close work from the pending state, >>> it means that smc_close_passive_work() has never been executed. >>> >>> You can find more details here. >>> >>> /** >>> * cancel_work_sync - cancel a work and wait for it to finish >>> * @work:the work to cancel >>> * >>> * Cancel @work and wait for its execution to finish. This function >>> * can be used even if the work re-queues itself or migrates to >>> * another workqueue. On return from this function, @work is >>> * guaranteed to be not pending or executing on any CPU. >>> * >>> * cancel_work_sync(&delayed_work->work) must not be used for >>> * delayed_work's. Use cancel_delayed_work_sync() instead. >>> * >>> * The caller must ensure that the workqueue on which @work was last >>> * queued can't be destroyed before this function returns. >>> * >>> * Return: >>> * %true if @work was pending, %false otherwise. >>> */ >>> boolcancel_work_sync(structwork_struct *work) >>> { >>> return__cancel_work_timer(work, false); >>> } >>> >>> Best wishes, >>> D. Wythe >> As I understand, queue_work() would wake up the work if the work is >> not already on the queue. And the sock_hold() is just prio to the >> queue_work(). That means, cancel_work_sync() would cancel the work >> either before its execution or after. If your fix refers to the former >> case, at this moment, I don't think the reference can be hold, thus it >> is unnecessary to put it. >>> > > I am quite confuse about why you think when we cancel the work before > its execution, > the reference can not be hold ? > > > Perhaps the following diagram can describe the problem in better way : > > smc_close_cancel_work > smc_cdc_msg_recv_action > > > sock_hold > queue_work >                                                                if > (cancel_work_sync())        // successfully cancel before execution > sock_put()                        //  need to put it since we already > hold a ref before   queue_work() > > ha, I already thought you might ask such question:P I think here two Problems need to be clarified: 1) Do you think the bh_lock_sock/bh_unlock_sock in the smc_cdc_msg_recv does not protect the smc_cdc_msg_recv_action() from cancel_work_sync()? Maybe that would go back to the discussion in the other patch on the behaviors of the locks. 2) If the queue_work returns true, as I said in the last main, the work should be (being) executed. How could the cancel_work_sync() cancel the work before execution successgully? >>>>> Fixes: 42bfba9eaa33 ("net/smc: immediate termination for SMCD link >>>>> groups") >>>>> Signed-off-by: D. Wythe >>>>> --- >>>>>   net/smc/smc_close.c | 3 ++- >>>>>   1 file changed, 2 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/net/smc/smc_close.c b/net/smc/smc_close.c >>>>> index 449ef45..10219f5 100644 >>>>> --- a/net/smc/smc_close.c >>>>> +++ b/net/smc/smc_close.c >>>>> @@ -116,7 +116,8 @@ static void smc_close_cancel_work(struct >>>>> smc_sock *smc) >>>>>       struct sock *sk = &smc->sk; >>>>>         release_sock(sk); >>>>> -    cancel_work_sync(&smc->conn.close_work); >>>>> +    if (cancel_work_sync(&smc->conn.close_work)) >>>>> +        sock_put(sk); >>>>>       cancel_delayed_work_sync(&smc->conn.tx_work); >>>>>       lock_sock(sk); >>>>>   } >>> > >