From patchwork Mon Nov 20 17:36:31 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Elliot Berman X-Patchwork-Id: 13461664 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=quicinc.com header.i=@quicinc.com header.b="La3sMofq" Received: from mx0b-0031df01.pphosted.com (mx0b-0031df01.pphosted.com [205.220.180.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A3CD2131; Mon, 20 Nov 2023 09:36:54 -0800 (PST) Received: from pps.filterd (m0279873.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 3AKHGVjB020976; Mon, 20 Nov 2023 17:36:44 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h=from : date : subject : mime-version : content-type : content-transfer-encoding : message-id : references : in-reply-to : to : cc; s=qcppdkim1; bh=JbCQVIXqkNI2H2MAYTXCqiy7vmoSbLN+sWhONQVWWSE=; b=La3sMofqd+WN1wbl9ix7XINzkPV7O+AZHLwTo3dsPuo9fs+Znz2jBl+D6qrQcsiDDhk3 oU/ZhqUCJRtbpBI054rBUjCh6Feu+VuZgQYNklJzA4SV+1KCTC3D6p/d/GUNFT8iHs7i bkeZJawWCdjXnQtVoir2KpguZu1ynWLpv6TNKben2h4gmjpjL3bd3jol3iSBVqFri4eH c4zR5dB6qils+c9H/qiipzjlKW2VtDO+ZRgFmQvX4bfKCqpMao+rbeAQ8DH3igi3tf7p 4FF0unywaB6esJllJPM70RGi9N1CaduTbVcn+AW7IAK0KBdKq4xbSzil647e50oIkCaU FQ== Received: from nasanppmta04.qualcomm.com (i-global254.qualcomm.com [199.106.103.254]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 3ug7ea8rjq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 20 Nov 2023 17:36:44 +0000 Received: from nasanex01b.na.qualcomm.com (nasanex01b.na.qualcomm.com [10.46.141.250]) by NASANPPMTA04.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 3AKHahKQ011372 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 20 Nov 2023 17:36:43 GMT Received: from hu-eberman-lv.qualcomm.com (10.49.16.6) by nasanex01b.na.qualcomm.com (10.46.141.250) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.40; Mon, 20 Nov 2023 09:36:42 -0800 From: Elliot Berman Date: Mon, 20 Nov 2023 09:36:31 -0800 Subject: [PATCH 1/2] freezer,sched: do not restore saved_state of a thawed task Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <20231120-freezer-state-multiple-thaws-v1-1-f2e1dd7ce5a2@quicinc.com> References: <20231120-freezer-state-multiple-thaws-v1-0-f2e1dd7ce5a2@quicinc.com> In-Reply-To: <20231120-freezer-state-multiple-thaws-v1-0-f2e1dd7ce5a2@quicinc.com> To: "Rafael J. Wysocki" , Pavel Machek , "Ingo Molnar" , "Peter Zijlstra (Intel)" CC: , Pavan Kondeti , "Aiqun Yu (Maria)" , , , Elliot Berman , Abhijeet Dharmapurikar X-Mailer: b4 0.13-dev X-Originating-IP: [10.49.16.6] X-ClientProxiedBy: nalasex01c.na.qualcomm.com (10.47.97.35) To nasanex01b.na.qualcomm.com (10.46.141.250) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: 8W7odmxie3OejK1QtSb8I4tvck-TU7eD X-Proofpoint-ORIG-GUID: 8W7odmxie3OejK1QtSb8I4tvck-TU7eD X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.272,Aquarius:18.0.987,Hydra:6.0.619,FMLib:17.11.176.26 definitions=2023-11-20_17,2023-11-20_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 phishscore=0 mlxscore=0 spamscore=0 malwarescore=0 priorityscore=1501 mlxlogscore=999 bulkscore=0 impostorscore=0 adultscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2311060000 definitions=main-2311200126 It is possible for a task to be thawed multiple times when mixing the *legacy* cgroup freezer and system-wide freezer. To do this, freeze the cgroup, do system-wide freeze/thaw, then thaw the cgroup. When this happens, then a stale saved_state can be written to the task's state and cause task to hang indefinitely. Fix this by only trying to thaw tasks that are actually frozen. This change also has the marginal benefit avoiding unnecessary wake_up_state(p, TASK_FROZEN) if we know the task is already thawed. There is not possibility of time-of-compare/time-of-use race when we skip the wake_up_state because entering/exiting TASK_FROZEN is guarded by freezer_lock. Fixes: 8f0eed4a78a8 ("freezer,sched: Use saved_state to reduce some spurious wakeups") Reviewed-by: Abhijeet Dharmapurikar Signed-off-by: Elliot Berman --- kernel/freezer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/freezer.c b/kernel/freezer.c index c450fa8b8b5e..759006a9a910 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -201,7 +201,7 @@ void __thaw_task(struct task_struct *p) if (WARN_ON_ONCE(freezing(p))) goto unlock; - if (task_call_func(p, __restore_freezer_state, NULL)) + if (!frozen(p) || task_call_func(p, __restore_freezer_state, NULL)) goto unlock; wake_up_state(p, TASK_FROZEN);