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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable 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 962DEC433E6 for ; Fri, 12 Mar 2021 13:27:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4C34964FEE for ; Fri, 12 Mar 2021 13:27:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231179AbhCLN0x (ORCPT ); Fri, 12 Mar 2021 08:26:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:48620 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229487AbhCLN0f (ORCPT ); Fri, 12 Mar 2021 08:26:35 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id AC21A64F70; Fri, 12 Mar 2021 13:26:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1615555595; bh=6+yq/fh98KG2tk+iUkCDYYsnXXXG791saZHy/yFzcic=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Wahbby+XZCJwMS5jQQBs9/BOKxHu6kyOkcu+UnYfUvPzgBxyx/LOuZSFGn66VST5d ybnx9T7M4RL4PTvR4GfP28uFP7o5tN/C8iXBd/7SgoHYAyy860rotxRqveSPj0tWw3 wXT6p2VhYAxozLI4uDT6ZdhvEb2QxONtMVtTP4ac= Date: Fri, 12 Mar 2021 14:26:32 +0100 From: Greg KH To: Zheng Yejian Cc: lee.jones@linaro.org, stable@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, cj.chengjian@huawei.com, judy.chenhui@huawei.com, zhangjinhao2@huawei.com, nixiaoming@huawei.com Subject: Re: [PATCH 4.4 v2 0/3] Backport patch series to update Futex from 4.9 Message-ID: References: <20210311032600.2326035-1-zhengyejian1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210311032600.2326035-1-zhengyejian1@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 11, 2021 at 11:25:57AM +0800, Zheng Yejian wrote: > Changelog for 'v2': > Complete commit messages with needed git commit ids as Greg and Lee suggested. > > Lee sent a patchset to update Futex for v4.9, see https://www.spinics.net/lists/stable/msg443081.html, > Then Xiaoming sent a follow-up patch for it, see https://lore.kernel.org/lkml/20210225093120.GD641347@dell/. > > These 3 patches is directly picked from v4.9, > and they may also resolve following issues in 4.4.260 which have been reported in v4.9, > see https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/?h=linux-4.4.y&id=319f66f08de1083c1fe271261665c209009dd65a > > /* > > * The task is on the way out. When the futex state is > > * FUTEX_STATE_DEAD, we know that the task has finished > > * the cleanup: > > */ > > int ret = (p->futex_state = FUTEX_STATE_DEAD) ? -ESRCH : -EAGAIN; > > Here may be: > int ret = (p->futex_state == FUTEX_STATE_DEAD) ? -ESRCH : -EAGAIN; > > > raw_spin_unlock_irq(&p->pi_lock); > > /* > > * If the owner task is between FUTEX_STATE_EXITING and > > * FUTEX_STATE_DEAD then store the task pointer and keep > > * the reference on the task struct. The calling code will > > * drop all locks, wait for the task to reach > > * FUTEX_STATE_DEAD and then drop the refcount. This is > > * required to prevent a live lock when the current task > > * preempted the exiting task between the two states. > > */ > > if (ret == -EBUSY) > > And here, the variable "ret" may only be "-ESRCH" or "-EAGAIN", but not "-EBUSY". > > > *exiting = p; > > else > > put_task_struct(p); > > Since 074e7d515783 ("futex: Ensure the correct return value from futex_lock_pi()") has > been merged in 4.4.260, I send the remain 3 patches. > > Peter Zijlstra (1): > futex: Change locking rules > > Thomas Gleixner (2): > futex: Cure exit race > futex: fix dead code in attach_to_pi_owner() > > kernel/futex.c | 209 +++++++++++++++++++++++++++++++++++++++++-------- > 1 file changed, 177 insertions(+), 32 deletions(-) All now queued up, thanks. greg k-h