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 E9A59C433F5 for ; Fri, 22 Apr 2022 14:24:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1448659AbiDVO05 (ORCPT ); Fri, 22 Apr 2022 10:26:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45200 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1448616AbiDVO0u (ORCPT ); Fri, 22 Apr 2022 10:26:50 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 2104D5B3DE for ; Fri, 22 Apr 2022 07:23:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1650637433; 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=m5YJ3ZOangNrQFwe/N/MOLWQjBg4jctW+Ug/shMSmLs=; b=EvQQHax+lfmnqu1qZD1HwySUrVw/OqdLIK5PUqyvr6wr82QTjVGwhCRlzVO8t9fxwmxnoT pO8Mz2Bw8UvHCEWej29GDyUXTVZsiW4m/lMib5gYcyXqtCkosheHtixnT1lUMZcdLt8qp6 G57fGeCkrpwJbjqYx6ReBa9WvtQdN+0= Received: from mail-qt1-f197.google.com (mail-qt1-f197.google.com [209.85.160.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-517-a_417ICDN4qTvZW-wCDPYg-1; Fri, 22 Apr 2022 10:23:52 -0400 X-MC-Unique: a_417ICDN4qTvZW-wCDPYg-1 Received: by mail-qt1-f197.google.com with SMTP id e6-20020ac86706000000b002f1f8ec1f63so5111373qtp.5 for ; Fri, 22 Apr 2022 07:23:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=m5YJ3ZOangNrQFwe/N/MOLWQjBg4jctW+Ug/shMSmLs=; b=KkkJ2VdRPUnmGO2Nk++y6oCyUDhWUmRf3GNwkG/yitGW7W/QqA9R8M8wKYL/F497a0 ZlX1JzWUR8Vgr9coGPD57NKZlRyKSHf2lQNKAIeGxQwV+09grfd5Rz6dhQXsVKOFk45z YMsW6mt//CLaNHs5sFsaOGllpYDqhtBDhuk5KnNjoO/TYseTRNQ+yX6xRxdATS+VzmLN gnzjLRSOLOCg3yfS5zdgZ569WekGXFjv9l/cpqq2DSFZk4W/6RAnzseifvq2KrgtET3f IdevDOVroJfrColyeNx9VPnCl8xwx1HXu9zEOhe+VyBHBYbUxwh+FkvG3L0WSyL4RFQI rElw== X-Gm-Message-State: AOAM533VD/+eiaO5SJePS+PkKAivx+1b5MACTMxvrgJF7NQ+BCPjXq+S zq/paqdvbm9sZkJs213ZsLsS1L9wEGAtxvBNAagSg4oo/3DBwo7rOtcwMIffRJc7edozU9LGOLk MfdrgNN0eBJnsK074WuozvN4y X-Received: by 2002:ad4:594c:0:b0:449:95d6:d715 with SMTP id eo12-20020ad4594c000000b0044995d6d715mr3786539qvb.115.1650637432237; Fri, 22 Apr 2022 07:23:52 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxeLkSB2S0gw2q64KND3DSjWD8vVsfApjfMfd+LxLs9iSGd95VAE5w8kpdBoELJg6WEgj6y/Q== X-Received: by 2002:ad4:594c:0:b0:449:95d6:d715 with SMTP id eo12-20020ad4594c000000b0044995d6d715mr3786530qvb.115.1650637432046; Fri, 22 Apr 2022 07:23:52 -0700 (PDT) Received: from ?IPV6:2600:1700:5610:6e80::41? ([2600:1700:5610:6e80::41]) by smtp.gmail.com with ESMTPSA id o21-20020a37a515000000b0069e6c84e8basm967409qke.117.2022.04.22.07.23.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Apr 2022 07:23:51 -0700 (PDT) Message-ID: <90124b02-76b5-d775-ac7d-a2e9d7677fa1@redhat.com> Date: Fri, 22 Apr 2022 10:23:50 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [RFC 2/3] futex: exit: Print a warning when futex_cleanup fails Content-Language: en-US To: Thomas Gleixner Cc: Andrew Morton , Ingo Molnar , Peter Zijlstra , Darren Hart , Davidlohr Bueso , =?UTF-8?Q?Andr=c3=a9_Almeida?= , Arjan van de Ven , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox References: <20220421190533.1601879-1-npache@redhat.com> <20220421190533.1601879-3-npache@redhat.com> <87r15qrwdt.ffs@tglx> From: Nico Pache In-Reply-To: <87r15qrwdt.ffs@tglx> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/21/22 16:53, Thomas Gleixner wrote: > On Thu, Apr 21 2022 at 15:05, Nico Pache wrote: > >> The futex_cleanup routines currently fails silently. >> >> Allow the futex_cleanup routines to fail more verbosely so we can >> leave a message behind for easier debugging/error detecting. > > This is a free ticket to spam dmesg for any unpriviledged user. As Matthew pointed out, we'd want to rate limit this. I was also thinking we can limit this to debug kernels so unpriviledged users can not cause dmesg spamming in production configs. > >> Fixes: 0771dfefc9e5 ("[PATCH] lightweight robust futexes: core") > > There is nothing to fix, really. Fair enough, its been part of the design since inceptions. > > Robust futexes are best effort as I explained you before and spamming > dmesg won't help anything. It would have helped find the OOM/Robust Futex issue more quickly. It may also help detect breakages in the pthread code (or any other users of robust futex) if someone is doing something incorrectly. Just a thought though. If you think its pointless to proceed down this path I wont push forward. Cheers, -- Nico