From nobody Sun Feb 8 11:44:49 2026 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 DF7FDC001DB for ; Tue, 8 Aug 2023 18:52:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232311AbjHHSwm (ORCPT ); Tue, 8 Aug 2023 14:52:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45454 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235499AbjHHSwV (ORCPT ); Tue, 8 Aug 2023 14:52:21 -0400 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D8511A768 for ; Tue, 8 Aug 2023 10:06:11 -0700 (PDT) Received: by mail-qk1-x74a.google.com with SMTP id af79cd13be357-76c939bc1adso863973385a.3 for ; Tue, 08 Aug 2023 10:06:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1691514368; x=1692119168; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Ymit3zFEWIjWyELyB8FrEwDrQYWKERmL2cdBLLRpncg=; b=uATKww8C8iuNmq5K/nNL2TZ1RoKZ2lf8Udwev/WUIv+xt73/VYFR7POfB9NqlYawLr fFjA7oonJ6O/CzAycnXQorpgkf7Sutqk3c1VJEZAPvFn7RGHVCDUIy3KxapCP4pMnKjw sBT+s42fYb11lQ8DUlSiilqdqmfIvXov5RSHEy+SSPWvtnoJdFMAuTAn1CPv4W0FWtSF glExNj6G1w4VUcFmXoy1ehLeYERic5ZTAv3lGfouaSuy8Ob2jWj+vP0jpiOVh/IMNmWp kKCbrPWhrd6peQiKunvaTjhH45uA43v5uGjHOS9M55k7o1+nisGXvfbTy3ec5hx+jbCF KjPw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691514368; x=1692119168; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Ymit3zFEWIjWyELyB8FrEwDrQYWKERmL2cdBLLRpncg=; b=hl4KiGysQHS50OdYGLbS+Wdb28M/PB8tJCbE+pwZCbC1SYfAUF6Adi/T5JyVcGOXRL ZOVqHMPgenzV/FyTJxMjV8yztxvUK3QwSD8hw4P24JE84pqk6HhxbGyQ6wrzejFRxkdT 0KYquB7UEPssY0E4ph78BtRVatBanRZgB8CX7N6KNuQ+gxW+5eMh8nIDUgRyyM67QIrF ABD/qNw2xlN1fJ8xw6Yh9+qUIYQPMaXY1WcKQ7xz96OtxzBGP0/0a5pihRPNaV8oaVzE paB2ipw+MQ8QdVhTacyzd2uGhX4dWtwL3Ks4ZykaTvjuRNMzFNmshjIpeSjUnMEPq2Vf oz4A== X-Gm-Message-State: AOJu0YyFcELR/hcwb9dxw41R6wL7mYFFX6U4ESOMXd+jXnGY8FYMtMZq lECDUox1qv6Wwf341zaX9jynZLPGEJFVvdaygkHcV3TuyVivHrDyTys9mNODpAwHdhWU17Zzxei Nyyq3uoimtovn5Bhh0qQRN9E3/dC4sf4GSgNv1O2nhGJvgW8pV5NuVatp76INGw6LXJn7obc= X-Google-Smtp-Source: AGHT+IFtBEywd6rcRcrgJzjs0aS0ORYXNdltbuVrMFXOFw9bGdzgPs2KuGt4qxEZ/wllTfZha/bqiOJNj34Z X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a63:3ecf:0:b0:564:3087:dd22 with SMTP id l198-20020a633ecf000000b005643087dd22mr50812pga.9.1691476025927; Mon, 07 Aug 2023 23:27:05 -0700 (PDT) Date: Tue, 8 Aug 2023 06:26:42 +0000 In-Reply-To: <20230808062658.391595-1-jstultz@google.com> Mime-Version: 1.0 References: <20230808062658.391595-1-jstultz@google.com> X-Mailer: git-send-email 2.41.0.640.ga95def55d0-goog Message-ID: <20230808062658.391595-3-jstultz@google.com> Subject: [RFC][PATCH 2/3] test-ww_mutex: Fix potential workqueue corruption From: John Stultz To: LKML Cc: John Stultz , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , "Paul E . McKenney" , Joel Fernandes , Li Zhijian , Dietmar Eggemann , kernel-team@android.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Cc: "Paul E . McKenney" Cc: Joel Fernandes Cc: Li Zhijian Cc: Dietmar Eggemann Cc: kernel-team@android.com Signed-off-by: John Stultz --- 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 9bceba65858a..358d66150426 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -479,7 +479,6 @@ static void stress_inorder_work(struct work_struct *wor= k) } while (!time_after(jiffies, stress->timeout)); =20 kfree(order); - kfree(stress); } =20 struct reorder_lock { @@ -544,7 +543,6 @@ static void stress_reorder_work(struct work_struct *wor= k) list_for_each_entry_safe(ll, ln, &locks, link) kfree(ll); kfree(order); - kfree(stress); } =20 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); } =20 #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; =20 locks =3D kmalloc_array(nlocks, sizeof(*locks), GFP_KERNEL); if (!locks) return -ENOMEM; =20 + stress_array =3D kmalloc_array(nthreads, sizeof(*stress_array), + GFP_KERNEL); + if (!stress_array) { + kfree(locks); + return -ENOMEM; + } + for (n =3D 0; n < nlocks; n++) ww_mutex_init(&locks[n], &ww_class); =20 + count =3D 0; for (n =3D 0; nthreads; n++) { struct stress *stress; void (*fn)(struct work_struct *work); @@ -609,9 +614,7 @@ static int stress(int nlocks, int nthreads, unsigned in= t flags) if (!fn) continue; =20 - stress =3D kmalloc(sizeof(*stress), GFP_KERNEL); - if (!stress) - break; + stress =3D &stress_array[count++]; =20 INIT_WORK(&stress->work, fn); stress->locks =3D locks; @@ -626,6 +629,7 @@ static int stress(int nlocks, int nthreads, unsigned in= t flags) =20 for (n =3D 0; n < nlocks; n++) ww_mutex_destroy(&locks[n]); + kfree(stress_array); kfree(locks); =20 return 0; --=20 2.41.0.640.ga95def55d0-goog