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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 003A3C3F68F for ; Fri, 10 Jan 2020 04:52:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B87D42080D for ; Fri, 10 Jan 2020 04:52:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="uLOBwf7g" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B87D42080D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 575468E0006; Thu, 9 Jan 2020 23:52:04 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 4FE778E0001; Thu, 9 Jan 2020 23:52:04 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3C5C88E0006; Thu, 9 Jan 2020 23:52:04 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0057.hostedemail.com [216.40.44.57]) by kanga.kvack.org (Postfix) with ESMTP id 23B9E8E0001 for ; Thu, 9 Jan 2020 23:52:04 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 6EBDF348D for ; Fri, 10 Jan 2020 04:52:03 +0000 (UTC) X-FDA: 76360502526.16.name84_86571f1534f18 X-HE-Tag: name84_86571f1534f18 X-Filterd-Recvd-Size: 3468 Received: from mail-oi1-f193.google.com (mail-oi1-f193.google.com [209.85.167.193]) by imf43.hostedemail.com (Postfix) with ESMTP for ; Fri, 10 Jan 2020 04:52:03 +0000 (UTC) Received: by mail-oi1-f193.google.com with SMTP id n16so799797oie.12 for ; Thu, 09 Jan 2020 20:52:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=vlinJQxreNW0LgSHPxKHqjPCjfftwQydPg4qaMBMqAY=; b=uLOBwf7g0tzyDtdRmJRecwzNi4gLs3YTVmGXZmuRK9t1bycyxTxEcT03f4Jj1XQU1n tU71/YmmsbvP2dVbyJlKdq/z8kBEcDa+MApxrUQcJe712ZFbqLL9NZqAB7khQLox+MwC Dm7qxfPPx3STpsOgA2YA1SpXGETkF32KxpBM9JnSUO7V9RH2A8vlcSz+sRiJNcDPDXK4 b3jNsTFfT2yb0m+Hge1nb0q0Vxm9kEs9jjOePC9dklTQ9mxQFqn/1zaiMpK3x9y/9xrX VDc7YjSoAkGAxcelOrtEajhYF2GpwhrFEpt3RzaZY6V05Xb2ACtMhSvpfWkIS5ahOwuc 2liA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=vlinJQxreNW0LgSHPxKHqjPCjfftwQydPg4qaMBMqAY=; b=BB7E+q9kvbRHwlKX3emkpsnNsEvzoUHcuozOwtYPeHH28yvQopuAU7CVm8pTTB0o2A 4jXrYiic9DK/674XVozX4PmTTITpryzM9h5to3iWzsZBmhsBBy7O0KLZAO67+eWmUABV bcK+3/zRZ1guXXwvSx4+/vSWXkneKKyNDin0zUXo4+xtIohh+FHsiAvHaJZTArQtROoM Kbk+EVMwXJC3Umx83lIfn9K7SuT/8f8aFkk+bytr6qC6QyOjxpHqPtmLLFgcC8ROCNw8 Vz4L0Xv+gDrmE9zHIJ4kS295HA6RCp3D808yq25HwIUmSonM7QqE228wha2MKnpRtmib vmNA== X-Gm-Message-State: APjAAAWxHfn8g61t9eoy2T7ch2zF0XJwJoQLt9j7POYl2o0CXoVGHvYK hBjFhVSyXIGdZx6MYYlWOfj7TOLMZPpdnKwvZXM= X-Google-Smtp-Source: APXvYqzMKoLVp5l6PZowKodtclvYtR6R33nF6mAg+foENgKXM9Ziv54vxfZlM/u1CC23hIWvj4i3c8R5GG8UoDeeSgk= X-Received: by 2002:aca:3cd7:: with SMTP id j206mr842019oia.142.1578631922395; Thu, 09 Jan 2020 20:52:02 -0800 (PST) MIME-Version: 1.0 References: <20200109225646.22983-1-xiyou.wangcong@gmail.com> In-Reply-To: From: Cong Wang Date: Thu, 9 Jan 2020 20:51:51 -0800 Message-ID: Subject: Re: [PATCH] mm: avoid blocking lock_page() in kcompactd To: Yang Shi Cc: Linux Kernel Mailing List , Andrew Morton , Michal Hocko , Linux MM Content-Type: text/plain; charset="UTF-8" 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: On Thu, Jan 9, 2020 at 5:01 PM Cong Wang wrote: > I tried to dump the process stacks after we saw the hung task > with /proc/X/stack (apparently sysrq is not an option for production), > but I didn't find anything useful. I didn't see any other process > hung in lock_page() either, all mm-related kernel threads were sleeping > (non-D) at the time I debugged. So, it is possible there was some place > missing a unlock_page() too, which is too late to debug after the hung > task was reported. Never mind. I found the process locking the page, /proc/X/stack apparently fools me by hiding page fault stack. :-/