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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 6F28EC352BE for ; Sat, 18 Apr 2020 17:38:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1AB152072B for ; Sat, 18 Apr 2020 17:38:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587231524; bh=Nc8OhsFzQOJr/tZ0tnZenfidFaopuDzt197ESLvR4dg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ZO6JkTC/fSZfH42p+OTqZhdPrK6KYiowUVIYTrnxJymmbUDMIxhIbCzC79FUKlOQL 0Qa8RBNXMPlQg3/ClDlLi9at7Pxx2Uk6m/LcLcl9tHvMHh5KoIv7o0NwS3aoxGJuyb Aes+3TWfOAwfun8N5C6IG5ozJ3AOKEqT8CqtpU2k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726138AbgDRRin (ORCPT ); Sat, 18 Apr 2020 13:38:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:38424 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726121AbgDRRin (ORCPT ); Sat, 18 Apr 2020 13:38:43 -0400 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 79BBC20724; Sat, 18 Apr 2020 17:38:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587231522; bh=Nc8OhsFzQOJr/tZ0tnZenfidFaopuDzt197ESLvR4dg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lzGk+BMLwJlK+ZZyZVoMFcTWuzaJX3c6zlGLKk1V+tOHQI+FT8cMjNysUY2mgG8h6 R5y1Q7FqivmB3apwcX9KZ1SzwB+/mONRrz81TQ66k8oiLpU0FllAmDtS8lDA0I7eB7 Sthz0qVzdxs+PQGPcAZ6uK05cx3OyUup/Zo2rRjk= Date: Sat, 18 Apr 2020 13:38:41 -0400 From: Sasha Levin To: "Eric W. Biederman" Cc: gregkh@linuxfoundation.org, tglx@linutronix.de, stable@vger.kernel.org Subject: Re: FAILED: patch "[PATCH] posix-cpu-timers: Store a reference to a pid not a task" failed to apply to 5.6-stable tree Message-ID: <20200418173841.GD1809@sasha-vm> References: <158720526370190@kroah.com> <871rol3r7v.fsf@x220.int.ebiederm.org> <20200418160513.GB1809@sasha-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20200418160513.GB1809@sasha-vm> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sat, Apr 18, 2020 at 12:05:13PM -0400, Sasha Levin wrote: >On Sat, Apr 18, 2020 at 07:37:08AM -0500, Eric W. Biederman wrote: >> writes: >> >>>The patch below does not apply to the 5.6-stable tree. >>>If someone wants it applied there, or to any other stable or longterm >>>tree, then please email the backport, including the original git commit >>>id to . >> >>So for anyone who cares the fix I refer to in the commit comment is the >>workaround that keeps the past implementation from being a real problem. >> >>I just see this as code cleanup so I can remove the old workaround. The >>old workaround will cause posix_cpu_timers_exit_group to be called early >>on particular variants of multi-threaded exec, resulting in the >>corresponding cpu clock stopping. So this does represent a real fix. >> >>However using a cpu timer of another process to signal things in your >>process is rare, and the case is breaks is only in certain obscure >>variations of a multi-threaded exec. Further no one has to my knowledge >>complained in over a decade. >> >>If someone sees that fix as important, and something that needs to be >>backported, it will be easiest to backport my earlier cleanup patches >>in the same series. > >For 5.6, 5.5, and 5.4 it was enough to take: > > 60f2ceaa8111 ("posix-cpu-timers: Remove unnecessary locking around cpu_clock_sample_group") > >as a dependency. Based on the commit message there it should be safe so >I did just that. Ignore that, I've dropped it for now. -- Thanks, Sasha