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Wed, 11 Sep 2024 08:27:12 GMT Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B6C3420049; Wed, 11 Sep 2024 08:27:12 +0000 (GMT) Received: from smtpav06.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 82B1D20040; Wed, 11 Sep 2024 08:27:12 +0000 (GMT) Received: from li-1de7cd4c-3205-11b2-a85c-d27f97db1fe1.ibm.com (unknown [9.155.211.168]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTPS; Wed, 11 Sep 2024 08:27:12 +0000 (GMT) From: "Marc Hartmayer" To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, Lai Jiangshan , Valentin Schneider , Tejun Heo , Heiko Carstens , Sven Schnelle , Mete Durlu , Christian Borntraeger Subject: Re: [PATCH 1/4] workqueue: Reap workers via kthread_stop() and remove detach_completion In-Reply-To: References: <20240621073225.3600-1-jiangshanlai@gmail.com> <20240621073225.3600-2-jiangshanlai@gmail.com> <87le1sjd2e.fsf@linux.ibm.com> <87wmjj971b.fsf@linux.ibm.com> <87tten8obm.fsf@linux.ibm.com> Date: Wed, 11 Sep 2024 10:27:11 +0200 Message-ID: <87ikv28ujk.fsf@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: AxsTscz6KYFHfPwsnjdBGZl2QiVf6Idt X-Proofpoint-GUID: GCcFAGY7mKJiWFqTLnIj1AjxFfQrbfvC X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.60.29 definitions=2024-09-10_12,2024-09-09_02,2024-09-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 priorityscore=1501 bulkscore=0 spamscore=0 phishscore=0 lowpriorityscore=0 mlxscore=0 mlxlogscore=999 impostorscore=0 clxscore=1015 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2408220000 definitions=main-2409110060 On Wed, Sep 11, 2024 at 11:32 AM +0800, Lai Jiangshan wrote: > On Wed, Sep 11, 2024 at 11:23=E2=80=AFAM Lai Jiangshan wrote: >> >> Hello, Marc >> Hi Lai, [=E2=80=A6snip=E2=80=A6] >> >> I'm not familiar with s390 asm code, but it might be the case that >> `worker->pool` is NULL in the in worker_thread() since detach_worker() >> resets worker->pool to NULL. >> >> If it is the case, READ_ONCE(worker->pool) should be used in worker_thre= ad() >> to fix the problem. >> >> (It is weird to me if worker->pool is read multi-time in worker_thread() >> since it is used many times, but since READ_ONCE() is not used, it can >> be possible). > > Oh, it can be possible that the worker is created and then destroyed befo= re > being waken-up. And if it is the case, READ_ONCE() won't help. I'm going = to > explore if "worker->pool =3D NULL;" can be moved out from > detach_worker(). I=E2=80=99ll double check if my assumption is true or not (worker->poll =3D= =3D NULL). It may well be that my assumption is wrong. Thanks for having a look! > > Thanks > Lai --=20 Kind regards / Beste Gr=C3=BC=C3=9Fe Marc Hartmayer IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Wolfgang Wendt Gesch=C3=A4ftsf=C3=BChrung: David Faller Sitz der Gesellschaft: B=C3=B6blingen Registergericht: Amtsgericht Stuttgart, HRB 243294