From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B8725C4320A for ; Wed, 4 Aug 2021 16:00:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 961016109F for ; Wed, 4 Aug 2021 16:00:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239306AbhHDQBF (ORCPT ); Wed, 4 Aug 2021 12:01:05 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:24886 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236453AbhHDQBE (ORCPT ); Wed, 4 Aug 2021 12:01:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628092851; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kEsjrzEf989GiFesEbeonJ3m9TGKEwxRikvJxw0JX+4=; b=hHBwPjVnW4zFHjE5ud/FcUb8N3ZC0avvfDnrSDcPlwCdEb5WmoRWXighMsvCY/fhK1/Dbg mBhEbeuZ/5Vc4qvvvQhj0T9ZHBU09zauhgcv0UEne9x7dVu7dS97PIj4wWCSniBuD8OKtY AAyiHDvN75aiItuBQ+Uv0Jpl4W/r6Lc= Received: from mail-qt1-f198.google.com (mail-qt1-f198.google.com [209.85.160.198]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-170-QUmCwvq1PfKhTCq7SZ1haA-1; Wed, 04 Aug 2021 12:00:50 -0400 X-MC-Unique: QUmCwvq1PfKhTCq7SZ1haA-1 Received: by mail-qt1-f198.google.com with SMTP id k18-20020ac847520000b029028bf7425a59so1111039qtp.22 for ; Wed, 04 Aug 2021 09:00:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:subject:to:cc:references:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=kEsjrzEf989GiFesEbeonJ3m9TGKEwxRikvJxw0JX+4=; b=pcFRSeuLk/vQO/PNtKzitlH4kT1malZO9oR0pg4mWeuPybm4rX3ENfF1/HuX5daT8G RQLzuaf9NWQiAF6ZzLMZtQ+6KeHUH5FEH58MU2nIQa8qBhQebFywlrEpjhr7+Eezvw18 7WOAqRllnk5us5/OsNzmDhJihQlE1VAJCs948ESYjgytJtIVKFSu0z2Hs6cbQQCEQspK Bp3dL9LSr6uucTbO9aTqTprP0COvkyxIQRr9WNDlyGml1tgslyWZtpfEb+WbtBhex8DG 3jZ5xT8reWKcHTXRLkDxsKFt6ru8R6MnHXaXaS2dIMKkLrkYdY6g+L6f249bskfCkJ0q kFIw== X-Gm-Message-State: AOAM5331yqFXAsjrE3e6ffDtRtLRTrgrAjlL9ulVghcS8NyP4f5/MO53 kpx38JwMJ4WQKDTcR2hOlEY2S/lVmzTK+2GDQyIGKvP+x+ej4SiecxTdkShqOqXybkwFb5F+LuC 5T2kz9utOmfW7UZRfr4xGKUTD X-Received: by 2002:a05:620a:3c8:: with SMTP id r8mr115982qkm.19.1628092850005; Wed, 04 Aug 2021 09:00:50 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx1QX2uMiY0+tjFXi1oQjufonahM1RQ6aSelVwGVf8DR+eHT/HQ7Hgz4p3Zz9FvTypcufD6pQ== X-Received: by 2002:a05:620a:3c8:: with SMTP id r8mr115953qkm.19.1628092849770; Wed, 04 Aug 2021 09:00:49 -0700 (PDT) Received: from llong.remote.csb ([2601:191:8500:76c0::cdbc]) by smtp.gmail.com with ESMTPSA id j4sm1480452qkk.78.2021.08.04.09.00.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Aug 2021 09:00:49 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Subject: Re: [PATCH] mm/memcg: Disable task obj_stock for PREEMPT_RT To: Thomas Gleixner , Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Vlastimil Babka , Roman Gushchin Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Shakeel Butt , Muchun Song , Luis Goncalves , Sebastian Andrzej Siewior , Daniel Bristot de Oliveira , Linus Torvalds References: <20210803175519.22298-1-longman@redhat.com> <87h7g62jxm.ffs@tglx> <8953e099-356e-ee09-a701-f4c7f4cda487@redhat.com> Message-ID: Date: Wed, 4 Aug 2021 12:00:47 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <8953e099-356e-ee09-a701-f4c7f4cda487@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/3/21 9:40 PM, Waiman Long wrote: > On 8/3/21 7:21 PM, Thomas Gleixner wrote: >> To complete the analysis of drain_local_stock(). AFAICT that function >> can only be called from task context. So what is the purpose of this >> in_task() conditional there? >> >>     if (in_task()) >>            drain_obj_stock(&stock->task_obj); > I haven't done a full analysis to see if it can be called from task > context only. Maybe in_task() check isn't needed, but having it there > provides the safety that it will still work in case it can be called > from interrupt context. After looking at possible call chains that can lead to drain_local_stock(), one call chain comes from the allocation of slab objects which I had previously determined to be callable from interrupt context. So it is prudent to add a in_task() check here. Cheers, Longman From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH] mm/memcg: Disable task obj_stock for PREEMPT_RT Date: Wed, 4 Aug 2021 12:00:47 -0400 Message-ID: References: <20210803175519.22298-1-longman@redhat.com> <87h7g62jxm.ffs@tglx> <8953e099-356e-ee09-a701-f4c7f4cda487@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628092852; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kEsjrzEf989GiFesEbeonJ3m9TGKEwxRikvJxw0JX+4=; b=cXMGZoc1XvE4W9cQAKBpJWkPubhcJ9qMGvNcV4EmEML4tyhcmO3kYmSqJCxJ1i8cR2CODz kA7+oRqHSjZeIxAe98IMGZ0rM6eeh5iSL+5/rvr3Ch1C0Hp8nj7E1Pv9/vrA03HhAxvyLG zFLS6nEb6d2Mvb1v806pb1wkn3ZTwz0= In-Reply-To: <8953e099-356e-ee09-a701-f4c7f4cda487-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Content-Language: en-US List-ID: Content-Type: text/plain; charset="utf-8"; format="flowed" To: Thomas Gleixner , Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Vlastimil Babka , Roman Gushchin Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Shakeel Butt , Muchun Song , Luis Goncalves , Sebastian Andrzej Siewior , Daniel Bristot de Oliveira , Linus Torvalds On 8/3/21 9:40 PM, Waiman Long wrote: > On 8/3/21 7:21 PM, Thomas Gleixner wrote: >> To complete the analysis of drain_local_stock(). AFAICT that function >> can only be called from task context. So what is the purpose of this >> in_task() conditional there? >> >>     if (in_task()) >>            drain_obj_stock(&stock->task_obj); > I haven't done a full analysis to see if it can be called from task > context only. Maybe in_task() check isn't needed, but having it there > provides the safety that it will still work in case it can be called > from interrupt context. After looking at possible call chains that can lead to drain_local_stock(), one call chain comes from the allocation of slab objects which I had previously determined to be callable from interrupt context. So it is prudent to add a in_task() check here. Cheers, Longman