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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8300BC761AF for ; Tue, 28 Mar 2023 17:49:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229764AbjC1RtI (ORCPT ); Tue, 28 Mar 2023 13:49:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60780 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229749AbjC1RtH (ORCPT ); Tue, 28 Mar 2023 13:49:07 -0400 Received: from mail-ed1-x535.google.com (mail-ed1-x535.google.com [IPv6:2a00:1450:4864:20::535]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7956DDBE5 for ; Tue, 28 Mar 2023 10:49:05 -0700 (PDT) Received: by mail-ed1-x535.google.com with SMTP id er13so12018175edb.9 for ; Tue, 28 Mar 2023 10:49:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20210112.gappssmtp.com; s=20210112; t=1680025744; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=AqbE7OnUHsZ2+LRH4fu/PmF89EsJRI5zjHe+XmQVCDs=; b=AcESMi6Tg2n/wTojpHFGYu2mc0254BMahR7WXFU2zVr1NcQ+s53BTljFpeIkztOPZD 0aHsoJ3G5s4OycOCAjAOMGekHiqgs0q7mySZxqSKuAcwdT7mTALbB9ifAfB9AIpBTQxZ 77SxzXW8rSToW0hJofZQ49zOI3KVuRDag5eKqxw/f9AQ2AyaATGPm/ubHWEm4d3LnrDu fmDW6ShKYODDJ9EAe7FHBCkCMZ6PLv4Mtdar6MuRkkvF2TJWSME4HUKVL3vitSqOkEGg Xi9dKsgKvexVMivDuoNUUzIf/XqWuhItchnt1+Aw4oTYjjFOsgTI7bUhs1PnVw6AykQW emjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1680025744; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=AqbE7OnUHsZ2+LRH4fu/PmF89EsJRI5zjHe+XmQVCDs=; b=GQ3ZqhSRLfLtSWa3oifPscTxLpKOXszJPAdT+NTJjm40BZNUY3SkjfxGMDSqjGNuXy ko/pY3Bzl9ap6q+LJFpSVuGHRNhD/kUR/xlXtsA+KwJeEDn2lpaxhLClU2pcDcm7yvse 808aAPMGeiIom7+05mi58tvWjGvtP0oDrHxDdt2+JDQ3ZLhxM/GaCpQBHDQapcNXxH/G 8odBYolsKA+Y+FY+i0KuCl1os4oZrBzfTnx8Em5+4qRw3oakLZOSErF8zPLjnIAtyIk2 jT3uvG470Aw+XY8O6mbfOzaSBHHo0fP20jggX1PUuEt4wMB8dQFDy9LNueL+ulEYmbbD tynw== X-Gm-Message-State: AAQBX9e6JnLO3UMn+Ll4uUDIncPK28sPTf7LzXXACLKViVvVSQH905aj OCVY8V5VosuipgKhlgf+BSb8SA== X-Google-Smtp-Source: AKy350bAUU2oFiMTm5phz6lxAVuPkhaTa/v8Z1SDfrPzx5L1ctMYrdc6nb8Raqgi36OVzrqh8Pkl1A== X-Received: by 2002:a17:907:76f8:b0:939:c395:1b3 with SMTP id kg24-20020a17090776f800b00939c39501b3mr17143261ejc.31.1680025744032; Tue, 28 Mar 2023 10:49:04 -0700 (PDT) Received: from localhost ([2a02:8070:6387:ab20:5139:4abd:1194:8f0e]) by smtp.gmail.com with ESMTPSA id zc14-20020a170906988e00b00927f6c799e6sm15588135ejb.132.2023.03.28.10.49.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Mar 2023 10:49:03 -0700 (PDT) Date: Tue, 28 Mar 2023 13:49:02 -0400 From: Johannes Weiner To: Yosry Ahmed Cc: Tejun Heo , Josef Bacik , Jens Axboe , Zefan Li , Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , Michal =?iso-8859-1?Q?Koutn=FD?= , Vasily Averin , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Subject: Re: [PATCH v1 4/9] cgroup: rstat: add WARN_ON_ONCE() if flushing outside task context Message-ID: References: <20230328061638.203420-1-yosryahmed@google.com> <20230328061638.203420-5-yosryahmed@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230328061638.203420-5-yosryahmed@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Mar 28, 2023 at 06:16:33AM +0000, Yosry Ahmed wrote: > rstat flushing is too expensive to perform in irq context. > The previous patch removed the only context that may invoke an rstat > flush from irq context, add a WARN_ON_ONCE() to detect future > violations, or those that we are not aware of. > > Signed-off-by: Yosry Ahmed > --- > kernel/cgroup/rstat.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c > index d3252b0416b6..c2571939139f 100644 > --- a/kernel/cgroup/rstat.c > +++ b/kernel/cgroup/rstat.c > @@ -176,6 +176,8 @@ static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep) > { > int cpu; > > + /* rstat flushing is too expensive for irq context */ > + WARN_ON_ONCE(!in_task()); > lockdep_assert_held(&cgroup_rstat_lock); This seems a bit arbitrary. Why is an irq caller forbidden, but an irq-disabled, non-preemptible section caller is allowed? The latency impact on the system would be the same, right?