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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 B415DC433DF for ; Mon, 6 Jul 2020 12:52:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9575020786 for ; Mon, 6 Jul 2020 12:52:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="B1r3fG6d" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728940AbgGFMwf (ORCPT ); Mon, 6 Jul 2020 08:52:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40668 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728967AbgGFMwf (ORCPT ); Mon, 6 Jul 2020 08:52:35 -0400 Received: from mail-lj1-x234.google.com (mail-lj1-x234.google.com [IPv6:2a00:1450:4864:20::234]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2FDC7C08C5DF for ; Mon, 6 Jul 2020 05:52:35 -0700 (PDT) Received: by mail-lj1-x234.google.com with SMTP id q4so9449580lji.2 for ; Mon, 06 Jul 2020 05:52:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=r/l418RqBKygT3XUaVVUWM37eZi8gQrBBNYXDXbn38k=; b=B1r3fG6dsH/qouMx2ubARUPAdcsyFNEgp1v1D8jfa52c8J7fRImq0ys4SnNlP6XrN2 99Raf5nlxeqcQN1Tn47ilpKlji+mfh9L+e+Rup7zFPMbiIFcs8P2uqJ4ASVgCVZ66Hl3 6/zGA4OKUhaVEjYmTMnmmU1m9r5vvu7tNcDRxLkBGD8VQXhgpGDcZzSvZFhoW7xr7Ugo seaC0JArz8AlAHcKsDf4KJxiCUXx/Jd+yuiCpMAl4YopCCdiTLEoUUy+wjdBQ17l/PUy FYI8QkWPGr6GT3rclGkWVFo64BXFXCZb4R0vyPT+BKs0jBiNdc13WXKOOvLxnvW2WDNJ xcPA== 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=r/l418RqBKygT3XUaVVUWM37eZi8gQrBBNYXDXbn38k=; b=fu+8zPW1OsmGp8rLVlkepfQeiB0hg2HJT0c39SAXDy60fZORcgjj31bmNoL2NxCFOl VqQbr440d4snX5WVg2OKzpLv8T4IcCdwkWIwJ+ImcHodPsq8lNl6AU+V83ncqz8YOTJM h4T/jPpaNOnhz4dbt3zPj1eeWiw5tHLFTn1PTvmrRgYbwzb/sEu+UBiggh+LXfEgrHW7 TsX+V24LjRFLyNk6BSR9d0uaG4PteOz4DwJuyk2Rl59/l7hX8yvn1pekzabLFmEucnZu jM0re7TzpNNIh/3Z9EIV0/JJX+YDMHG7JQwZqpQtsMYWb1sHIEGVRj2axq7gdYrSx5VS +y2A== X-Gm-Message-State: AOAM530BBfgait/V2VHL3NLX3AmBZV3rsgxqF7hcfjquq8/9RCq75iDe sFFaLFic2dawQyGhP/5gDoFKpS3SvP5erTIKQCj6qw== X-Google-Smtp-Source: ABdhPJwjpTKLYWq+hR31eDYdmY+r8r9swuzWK5B3LmVV+w60tAqfgVu13/vDXFsFyS2tITflFJ5EFbHXt6vJDWkzwko= X-Received: by 2002:a05:651c:3cf:: with SMTP id f15mr26115232ljp.365.1594039953375; Mon, 06 Jul 2020 05:52:33 -0700 (PDT) MIME-Version: 1.0 References: <20200703224411.GC25072@amd> <20200704114820.GA16083@amd> <57ab4fb3-3f82-d34f-ad74-2214b45a4dd9@amazon.com> In-Reply-To: <57ab4fb3-3f82-d34f-ad74-2214b45a4dd9@amazon.com> From: Jann Horn Date: Mon, 6 Jul 2020 14:52:07 +0200 Message-ID: Subject: Re: [RFC]: mm,power: introduce MADV_WIPEONSUSPEND To: Alexander Graf Cc: Pavel Machek , "Catangiu, Adrian Costin" , "linux-mm@kvack.org" , "linux-pm@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "linux-api@vger.kernel.org" , "akpm@linux-foundation.org" , "rjw@rjwysocki.net" , "len.brown@intel.com" , "mhocko@kernel.org" , "fweimer@redhat.com" , "keescook@chromium.org" , "luto@amacapital.net" , "wad@chromium.org" , "mingo@kernel.org" , "bonzini@gnu.org" , "MacCarthaigh, Colm" , "Singh, Balbir" , "Sandu, Andrei" , "Brooker, Marc" , "Weiss, Radu" , "Manwaring, Derek" Content-Type: text/plain; charset="UTF-8" Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Mon, Jul 6, 2020 at 2:27 PM Alexander Graf wrote: > Unless we create a vsyscall that returns both the PID as well as the > epoch and thus handles fork *and* suspend. I need to think about this a > bit more :). You can't reliably detect forking by checking the PID if it is possible for multiple forks to be chained before the reuse check runs: - pid 1000 remembers its PID - pid 1000 forks, creating child pid 1001 - pid 1000 exits and is waited on by init - the pid allocator wraps around - pid 1001 forks, creating child pid 1000 - child with pid 1000 tries to check for forking, determines that its PID is 1000, and concludes that it is still the original process