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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 C109DC47256 for ; Tue, 5 May 2020 19:00:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B40B20663 for ; Tue, 5 May 2020 19:00:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="PLxoH++/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729108AbgEETAj (ORCPT ); Tue, 5 May 2020 15:00:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728707AbgEETAh (ORCPT ); Tue, 5 May 2020 15:00:37 -0400 Received: from mail-qk1-x742.google.com (mail-qk1-x742.google.com [IPv6:2607:f8b0:4864:20::742]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BDDF8C061A10 for ; Tue, 5 May 2020 12:00:36 -0700 (PDT) Received: by mail-qk1-x742.google.com with SMTP id i14so3456750qka.10 for ; Tue, 05 May 2020 12:00:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=GL8YJhagmr0tY88vQYg8nNJwc2RX2WgsOSH+iUm5Ykg=; b=PLxoH++/yyfuORzgoSUMi8+9wHSL4/iBxLjFFQCziWAODruKOY8aWMCJ3PL63O01p6 25TvRIvBTL0olryOCHVe+rJDB+YKESxFqnzLRYdheZCWTBmQS65FAbJo/A5bNrcJMVQv QQzx5+x4xfF/d6+LvRG8TE9Xa1Hv54kUYu4MicCAIpMjQahvcqXH1u0eyzSC3cKgSx3F sXEQiZIomrwDrNCWwdF7BvnYl3TWqNWZjoLyULrJwJrksYIHaRh8ssyT8Ea41CJG5Wsy Ry/9MZrQT0KIwKBBvYn74fNzfBhHkrqCqMUQvFyvNzQOQyzzeugg9I/zXseBfcma9J3e xzUw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=GL8YJhagmr0tY88vQYg8nNJwc2RX2WgsOSH+iUm5Ykg=; b=Lm2lcKWIy/8dqp7kSesKnOyRZZFYAfq0bxf4ZAB8H73ogvA2/bVC4i7qkvP9WebWyw W0lsNfYVbqTNgWbhERbw7kg9ID6BsGR80m9GKVTdTefncEpGM6h9AXw6EbkOcNaDWfTG jGx3pY8VUC5NFnBHOdMXcP0li3H9R1pBd6fw4Pf0LL38moqiyBmMH3KF2GXRFBGsU3rV 4ddHMR+I9nU12v5C3iX18oOWx18ICJ5dtS0D8XEvLy8BJv2i8b06Mu1Zblcm1HCrkWPT GKqD4W36nPXJ0EpXIvpwDfu/zP1dE19y1l+t4SaVVmWpx/o2NjSW0D5yuSDqXG2iiXqD qKSA== X-Gm-Message-State: AGi0PuanFpFnZEftP2wbaEUbd5S+VBy87Foah643Ish8EYNLEL3Lxw0L WBTMGmg2EYtehufiwHzE6wf9zA== X-Google-Smtp-Source: APiQypKlB2SJjOgo2QNo0+920N+E3iInb3Z7GmJ3C4z4rOKuQVKs3mtv8XHi42+Up8m6GIZeLEq4Bw== X-Received: by 2002:a37:6145:: with SMTP id v66mr5004657qkb.458.1588705235839; Tue, 05 May 2020 12:00:35 -0700 (PDT) Received: from [192.168.1.153] (pool-71-184-117-43.bstnma.fios.verizon.net. [71.184.117.43]) by smtp.gmail.com with ESMTPSA id z65sm2563832qka.60.2020.05.05.12.00.34 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 May 2020 12:00:35 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.80.23.2.2\)) Subject: Re: splice() rcu_sched self-detected stall on CPU From: Qian Cai In-Reply-To: <20200505185732.GP2869@paulmck-ThinkPad-P72> Date: Tue, 5 May 2020 15:00:34 -0400 Cc: Al Viro , LKML , linux-fsdevel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <8678900D-8D52-4195-A767-9E6923EE0AAF@lca.pw> References: <89F418A9-EB20-48CB-9AE0-52C700E6BB74@lca.pw> <20200505185732.GP2869@paulmck-ThinkPad-P72> To: "Paul E. McKenney" X-Mailer: Apple Mail (2.3608.80.23.2.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On May 5, 2020, at 2:57 PM, Paul E. McKenney = wrote: >=20 > On Mon, May 04, 2020 at 03:11:09PM -0400, Qian Cai wrote: >> Running a syscall fuzzer inside a container on linux-next floods = systems with soft lockups. It looks like stuck in this line at = iov_iter_copy_from_user_atomic(), Thoughts? >>=20 >> iterate_all_kinds(i, bytes, v, >> copyin((p +=3D v.iov_len) - v.iov_len, v.iov_base, = v.iov_len), >> memcpy_from_page((p +=3D v.bv_len) - v.bv_len, = v.bv_page, >> v.bv_offset, v.bv_len), >> memcpy((p +=3D v.iov_len) - v.iov_len, v.iov_base, = v.iov_len) >> ) >=20 > If the size being copied is large enough, something like this might = happen. >=20 > Is this a CONFIG_PREEMPT=3Dn kernel? And is the size passed in to Yes, CONFIG_PREEMPT=3Dn. > iov_iter_copy_from_user_atomic() quite large, given that this is = generated > by a fuzzer? If so, one thing to try is to add cond_resched() in the > iterate_bvec(), iterate_kvec(), and iterate_iovec() macros. I=E2=80=99ll try that.=