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 9B07ECD4F30 for ; Fri, 22 Sep 2023 08:12:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232417AbjIVIMU (ORCPT ); Fri, 22 Sep 2023 04:12:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232482AbjIVILq (ORCPT ); Fri, 22 Sep 2023 04:11:46 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA46BE4B; Fri, 22 Sep 2023 01:11:39 -0700 (PDT) Date: Fri, 22 Sep 2023 08:11:37 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1695370298; h=from:from:sender:sender:reply-to: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=FZqsvjjlEWZGBL4cgJ2JxgAJVbdahw8bEqqnuOXhUxc=; b=tb+Qqq9JnLV863K0PuaWNgk7/nrLIQ4fTVxh8YzJOTAKznP4a+nfPHWz43NGLlnaCUhrjW zgsoyiSBlVDmKgJXmtYlOr5P/OdVDAfJYtmh5v+ng9lf5NqnDYcp4to79yloGraKqczZkg dMYLirHQn6cnDnrtqE6yI917N+7+lRnHljfCyFhu3OaLzap19r0MbO7XaHo7HkJT4L5v+p KJKSZ6AAJcMh3W2V3+JsmfgmcfO/YmUXdx6sCS3Vbjh0nXHJR0lWJ25Wt7aew95Lh1qcBP 5WI8YcDBqGikRvlUao3iwgyT7KqLmkpGe4cBTlzeBfEixcNoHiGwK0zcsIpGSQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1695370298; h=from:from:sender:sender:reply-to: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=FZqsvjjlEWZGBL4cgJ2JxgAJVbdahw8bEqqnuOXhUxc=; b=hSUvho8pyGAJcA9ZiZns7v977eVto5De55HjK5ate/H+iZQ5khb/xso39TEdNZ4EGtkFq1 02EGbC28jJfgz4DQ== From: "tip-bot2 for John Stultz" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: locking/core] locking/ww_mutex/test: Fix potential workqueue corruption Cc: John Stultz , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230922043616.19282-3-jstultz@google.com> References: <20230922043616.19282-3-jstultz@google.com> MIME-Version: 1.0 Message-ID: <169537029753.27769.15529645927257680234.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the locking/core branch of tip: Commit-ID: bccdd808902f8c677317cec47c306e42b93b849e Gitweb: https://git.kernel.org/tip/bccdd808902f8c677317cec47c306e42b93b849e Author: John Stultz AuthorDate: Fri, 22 Sep 2023 04:36:00 Committer: Ingo Molnar CommitterDate: Fri, 22 Sep 2023 09:43:40 +02:00 locking/ww_mutex/test: Fix potential workqueue corruption In some cases running with the test-ww_mutex code, I was seeing odd behavior where sometimes it seemed flush_workqueue was returning before all the work threads were finished. Often this would cause strange crashes as the mutexes would be freed while they were being used. Looking at the code, there is a lifetime problem as the controlling thread that spawns the work allocates the "struct stress" structures that are passed to the workqueue threads. Then when the workqueue threads are finished, they free the stress struct that was passed to them. Unfortunately the workqueue work_struct node is in the stress struct. Which means the work_struct is freed before the work thread returns and while flush_workqueue is waiting. It seems like a better idea to have the controlling thread both allocate and free the stress structures, so that we can be sure we don't corrupt the workqueue by freeing the structure prematurely. So this patch reworks the test to do so, and with this change I no longer see the early flush_workqueue returns. Signed-off-by: John Stultz Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20230922043616.19282-3-jstultz@google.com --- kernel/locking/test-ww_mutex.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c index 9bceba6..358d661 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -479,7 +479,6 @@ retry: } while (!time_after(jiffies, stress->timeout)); kfree(order); - kfree(stress); } struct reorder_lock { @@ -544,7 +543,6 @@ out: list_for_each_entry_safe(ll, ln, &locks, link) kfree(ll); kfree(order); - kfree(stress); } static void stress_one_work(struct work_struct *work) @@ -565,8 +563,6 @@ static void stress_one_work(struct work_struct *work) break; } } while (!time_after(jiffies, stress->timeout)); - - kfree(stress); } #define STRESS_INORDER BIT(0) @@ -577,15 +573,24 @@ static void stress_one_work(struct work_struct *work) static int stress(int nlocks, int nthreads, unsigned int flags) { struct ww_mutex *locks; - int n; + struct stress *stress_array; + int n, count; locks = kmalloc_array(nlocks, sizeof(*locks), GFP_KERNEL); if (!locks) return -ENOMEM; + stress_array = kmalloc_array(nthreads, sizeof(*stress_array), + GFP_KERNEL); + if (!stress_array) { + kfree(locks); + return -ENOMEM; + } + for (n = 0; n < nlocks; n++) ww_mutex_init(&locks[n], &ww_class); + count = 0; for (n = 0; nthreads; n++) { struct stress *stress; void (*fn)(struct work_struct *work); @@ -609,9 +614,7 @@ static int stress(int nlocks, int nthreads, unsigned int flags) if (!fn) continue; - stress = kmalloc(sizeof(*stress), GFP_KERNEL); - if (!stress) - break; + stress = &stress_array[count++]; INIT_WORK(&stress->work, fn); stress->locks = locks; @@ -626,6 +629,7 @@ static int stress(int nlocks, int nthreads, unsigned int flags) for (n = 0; n < nlocks; n++) ww_mutex_destroy(&locks[n]); + kfree(stress_array); kfree(locks); return 0;