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a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1755658392; bh=iZir/QKK5JTqAfdGmgVb/hXLInesr/tGQLazPkNll88=; h=Date:From:To:Cc:Subject:Content-Type; b=jtrroeHdkHuJtsqb5l11kvf1MI9vMHXSmzA44PUngxs/RwGTt4cGZSAvff5GR+dvm qhNeuI0ZNVn0oimGsMDmMMHhTd9hIHDPomPJjVHJFLe8MdtSSMIRhS7OiAW8SN4eGP DsqRBGt6MtWDWPc7dGFjAO1exLJ4MBOy2SB9POuEBvqkpdFRKIQlRjQ9QfBRiJYPDX ghHEi85tmIyqQK5NbHDoRbgVJYNaCIXho3a+xjphr1Z1S86DbPx0D70+9fVj73zujo e5jwSxu81ikpAoBx7AT9kUcMcFRAsY3WXPhGjHeva9aw9mCv3QuAtdEcIgiKY5olGR sovbvoUeJ/wPQ== Date: Tue, 19 Aug 2025 19:53:08 -0700 From: Davidlohr Bueso To: Michal Hocko Cc: zhongjinji , akpm@linux-foundation.org, andrealmeid@igalia.com, dvhart@infradead.org, feng.han@honor.com, liam.howlett@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, liulu.liu@honor.com, mingo@redhat.com, npache@redhat.com, peterz@infradead.org, rientjes@google.com, shakeel.butt@linux.dev, tglx@linutronix.de Subject: Re: [PATCH v4 2/3] mm/oom_kill: Only delay OOM reaper for processes using robust futexes Message-ID: <20250820025308.rkqlvauh4dz42oic@offworld> Mail-Followup-To: Michal Hocko , zhongjinji , akpm@linux-foundation.org, andrealmeid@igalia.com, dvhart@infradead.org, feng.han@honor.com, liam.howlett@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, liulu.liu@honor.com, mingo@redhat.com, npache@redhat.com, peterz@infradead.org, rientjes@google.com, shakeel.butt@linux.dev, tglx@linutronix.de References: <20250818120819.26709-1-zhongjinji@honor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20220429 X-Rspamd-Queue-Id: 541ACC000B X-Stat-Signature: aw4fa88c1e9dmyuuksadjq6uhyixt6ii X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1755658394-193940 X-HE-Meta: U2FsdGVkX1/lDCYCp/daoMWzAmpLHAP2hKSRLTjXB3GhRzqc8I3Y1V5eBABEQnzQnil+aRxXOemFeje/aoY1YtaAtFWzpLV+W+EUgDoHlnqNmSx+1Xfig9Pp73v82QVZ8y/DJj65tq/PY8esxrysaHDm6CwulNaw63a9MzDcFC9y0vWKk3L0e+ZUqhNzaf30qQs/pdkbalKt6uMsYXkRE5DN3qAxT4PUtJym5ZkOMd2JgxUeKr6fUwcyVnO2sB+voMXp7QwiO/lA5XAaZ9dyF0tBsIan+lTWVJ0OdDJp42sEQ0ozk45sfEFJcr7RYBCxcEJRp4GUFW0EIVhP+JQdTHdjqjZ16a2kZ4QQoKCyv3610gvYhZ9+TEvzC46Q8V9pEmZg8+90bAoNJ07m8vBiBPAlFdl44QRdG/Xck62Whv+8VAubLVbtwX3Ew8mVnlB8Jgiw/btnIF+XX4YK5c1R6ii4P5I4nnLYtAcIGrbXW9VNZz3hnEL34lwctFZb4HLVdpe7aidlF09eyPdoDXR2lob4yw/F9GW5M62kYj1dyAyRBgCQiBC9wlW4+M8WNrsTobztBB1ORImaLKQ5BWFN1p8DnVhH0VbmCUXUPG7GxlKjwDDI8gxgY39VK4UmXFvNxlN4NisbZkcL5tJVt+ZBgjNk2O/Ej5QaYAW2Gr2rNELnrU3sBA8kEqes3FLvYFr5O8hDkHkROKLdrb0WZDytrXyFmZkN804xef/tiL5Gs2HtvRbo+Si8UXxRQdwGiPYxCPF7orS5MEggOEIPebgL5ZF0hoOEHwVxV89riJjckfxpQhW/okUqVlE1s3U52vHCYlJiivXF0hdrY7C0I+K0mb5Nvu8ewg92FGGpLwN/ZEEGzEFUmkbH/Xox0f6VuJgmn30NTk0b3cMi1wMsgDMaXPMdVhHBv5HaaaEGz4LpYzS62u6iGDAoRFyTW/BBNjSqfQzRLRsPuKU+IE7I5za MkSbcYm2 ab2wRTqQqXZj49RYY1EeZSz1JfywDqiPfOYJL2gtfBhyHyRUVXa92HjC4489M1X9MtHclDCSFKTi3UCDW/zZFEks6GyQf+U0qdSp5ulJfImPUSbyW4WqucgK7kVsh1VxEcb/8hg6BpRILVSnFAXtUl4H7KB+jUes6aPg2zGQamRtfL76GT6eYiwFkztryt3MGWmBnF5qs/lkgyD3YiTD2yUezTfova/0zPCqqI+BXsQYaPV865gxzoCam5OoQhadK7b+uo7ZkFdCWmAt+2tW1vG9PNwatyTgVhnPIktJOScyCyp9EMJO/jGnng5yldhi2nbF6bHF+s152yckDQpkP42/jGw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 19 Aug 2025, Michal Hocko wrote: >On Mon 18-08-25 20:08:19, zhongjinji wrote: >> If a process holding robust futexes gets frozen, robust futexes might be reaped before >> futex_cleanup() runs when an OOM occurs. I am not sure if this will actually happen. > >Yes, and 2s delay will never rule that out. Especially for frozen tasks >which could be frozen undefinitely. That is not the point I have tried >to make. I was suggesting not treating futex specially because no matter >what we do this will always be racy and a hack to reduce the risk. We >simply cannot deal with that case more gracefully without a major >surgery to the futex implementation which is not desirable for this >specific reason. Yeah, relying on time as a fix is never a good idea. I was going to suggest skipping the reaping for tasks with a robust list, but that still requires the racy check, and your suggested workaround seems more practical. Thanks, Davidlohr