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Thu, 18 Apr 2024 05:54:39 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A5A3C2004E; Thu, 18 Apr 2024 05:54:37 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8D0ED2004D; Thu, 18 Apr 2024 05:54:37 +0000 (GMT) Received: from tuxmaker.linux.ibm.com (unknown [9.152.85.9]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Thu, 18 Apr 2024 05:54:37 +0000 (GMT) From: Sven Schnelle To: Tejun Heo Cc: Lai Jiangshan , linux-kernel@vger.kernel.org Subject: Re: [PATCH] workqueue: fix selection of wake_cpu in kick_pool() In-Reply-To: (Tejun Heo's message of "Wed, 17 Apr 2024 15:55:57 -1000") References: <20240415053550.538722-1-svens@linux.ibm.com> Date: Thu, 18 Apr 2024 07:54:37 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: h9g76LQhiScCVJ6WSnsVVYL1jmPc983- X-Proofpoint-GUID: pe_poYMMyp9JXmhABOKx908XPirAl4JQ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.1011,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2024-04-18_04,2024-04-17_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 priorityscore=1501 bulkscore=0 clxscore=1015 spamscore=0 adultscore=0 suspectscore=0 lowpriorityscore=0 impostorscore=0 malwarescore=0 mlxlogscore=738 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2404010000 definitions=main-2404180039 Tejun Heo writes: > Hello, > > On Wed, Apr 17, 2024 at 05:36:38PM +0200, Sven Schnelle wrote: >> > This generally seems like a good idea but isn't this still racy? The CPU may >> > go down between setting p->wake_cpu and wake_up_process(). >> >> Don't know without reading the source, but how does this code normally >> protect against that? > > Probably by wrapping determining the wake_cpu and the wake_up inside > cpu_read_lock() section. Thanks. Should i send a v2 and incorporate your additional changes or do you want to do that?