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Tue, 1 Feb 2022 23:26:53 +0000 Date: Tue, 1 Feb 2022 15:26:48 -0800 From: Roman Gushchin To: Tejun Heo CC: Andrew Morton , , , Alexander Egorenkov , Waiman Long , Johannes Weiner , Shakeel Butt , Jeremy Linton , Subject: Re: [PATCH RESEND] mm: memcg: synchronize objcg lists with a dedicated spinlock Message-ID: References: Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MWHPR1401CA0017.namprd14.prod.outlook.com (2603:10b6:301:4b::27) To BYAPR15MB4136.namprd15.prod.outlook.com (2603:10b6:a03:96::24) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: d04985f4-2a33-496e-678c-08d9e5da5419 X-MS-TrafficTypeDiagnostic: MWHPR15MB1517:EE_ X-Microsoft-Antispam-PRVS: X-FB-Source: Internal X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BYAPR15MB4136.namprd15.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230001)(366004)(6916009)(8936002)(7416002)(5660300002)(8676002)(54906003)(6666004)(4326008)(83380400001)(2906002)(6512007)(86362001)(9686003)(38100700002)(186003)(6486002)(52116002)(6506007)(508600001)(66476007)(66556008)(316002)(66946007)(67856001);DIR:OUT;SFP:1102; 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Objcg release path requires > > taking the css_set_lock, which is used to synchronize objcg lists. > > > > This can create a circular dependency with the sighandler lock, > > which is taken with the locked css_set_lock by the freezer code > > (to freeze a task). > > > > In general it seems that using css_set_lock to synchronize objcg lists > > makes any slab allocations and deallocation with the locked > > css_set_lock and any intervened locks risky. > > > > To fix the problem and make the code more robust let's stop using > > css_set_lock to synchronize objcg lists and use a new dedicated > > spinlock instead. > > > > Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") > > Signed-off-by: Roman Gushchin > > Reported-by: Alexander Egorenkov > > Tested-by: Alexander Egorenkov > > Reviewed-by: Waiman Long > > Cc: Tejun Heo > > Cc: Johannes Weiner > > Cc: Shakeel Butt > > Cc: Jeremy Linton > > Cc: cgroups@vger.kernel.org > > Acked-by: Tejun Heo Thank you! > > I suppose this will go through -mm? If you want me to route it through the > cgroup tree, please let me know. I think so, usually this stuff goes through @mm. Thanks! From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Gushchin Subject: Re: [PATCH RESEND] mm: memcg: synchronize objcg lists with a dedicated spinlock Date: Tue, 1 Feb 2022 15:26:48 -0800 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=date : from : to : cc : subject : message-id : references : content-type : in-reply-to : mime-version; s=facebook; bh=kWQGnlsnCQQMA5/UZrmR7fJWxEg/FG4Vtq3Dbuxs0wc=; b=aE8VBWGw+iLxQFmkF3hVYk0f5ik/T4l+rbo9tZSVNWhwkGAhMBHqVPTKP67FSrBy69Xg LxyFPZEJqGqfxLG3zCoykpl/pnoheAJexOpqmJTFtAyaS0BuFjvWtcr47hjuRM6IzHuu +zGPYuo/JH6KXiyl/H+ItTbD2cMP7pHBv1k= Content-Disposition: inline In-Reply-To: List-ID: Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: Andrew Morton , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Alexander Egorenkov , Waiman Long , Johannes Weiner , Shakeel Butt , Jeremy Linton , cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Tue, Feb 01, 2022 at 12:48:41PM -1000, Tejun Heo wrote: > On Tue, Feb 01, 2022 at 02:33:04PM -0800, Roman Gushchin wrote: > ... > > In this example a slab allocation from __send_signal() caused a > > refilling and draining of a percpu objcg stock, resulted in a > > releasing of another non-related objcg. Objcg release path requires > > taking the css_set_lock, which is used to synchronize objcg lists. > > > > This can create a circular dependency with the sighandler lock, > > which is taken with the locked css_set_lock by the freezer code > > (to freeze a task). > > > > In general it seems that using css_set_lock to synchronize objcg lists > > makes any slab allocations and deallocation with the locked > > css_set_lock and any intervened locks risky. > > > > To fix the problem and make the code more robust let's stop using > > css_set_lock to synchronize objcg lists and use a new dedicated > > spinlock instead. > > > > Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") > > Signed-off-by: Roman Gushchin > > Reported-by: Alexander Egorenkov > > Tested-by: Alexander Egorenkov > > Reviewed-by: Waiman Long > > Cc: Tejun Heo > > Cc: Johannes Weiner > > Cc: Shakeel Butt > > Cc: Jeremy Linton > > Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > > Acked-by: Tejun Heo Thank you! > > I suppose this will go through -mm? If you want me to route it through the > cgroup tree, please let me know. I think so, usually this stuff goes through @mm. Thanks!