From nobody Sun Feb 8 01:30:46 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 E8953E7D0C2 for ; Fri, 22 Sep 2023 04:36:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230410AbjIVEgp (ORCPT ); Fri, 22 Sep 2023 00:36:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56254 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230225AbjIVEge (ORCPT ); Fri, 22 Sep 2023 00:36:34 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D852E18F for ; Thu, 21 Sep 2023 21:36:28 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-d8571d5e71aso2203978276.0 for ; Thu, 21 Sep 2023 21:36:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1695357388; x=1695962188; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=FFCV0sch6yU/8LYuNDFjRf1SrTydnK4Yn1LXrMsCSk4=; b=yXERfMhY4eBgTkKkc75ZyeMIdpnGWdA75CrRE8zXbbt+Q7Xl0wlfNNATH2T4OfOpS7 w2t+T59imlmUC77GplKSx09TzP96vffUY54q2b90PsA0CvBJWBNNeCKa3lQgk9Pf4End 8OpP5yi1mYxQ6x41+89Kje2Ayg8xZ9sQZQNIhi0jdt6+tZdBOmkdbxXPWZdu0gdw8A0Z nW1keo/5k1zZM215s8/vzUmQU4EPj845jfAUZgC3o8c6Y/YDd9xXgLECz1UKbTX6/E8Y olcj83NMpKeA1llx9vAjD/L1up2+O8O8asL+gDhEhU92T/mFB5RlzzXmetqx/BVoyteI /n/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695357388; x=1695962188; 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=FFCV0sch6yU/8LYuNDFjRf1SrTydnK4Yn1LXrMsCSk4=; b=RoSOpqbEUqRdBDuvMBxUDQFVo+dhsQV/yVGTdM8pK46k14DbQ2OcObwR9jdE3aMfdh vKR+QmxtA5QY+zVcYXSGjD1gI/nJtk15rzOw4GeyFhH6As1KqWMjRfHD9HBxQOnsOIkN VYuj5qzhNkVkLRcHMk/9pWoaLdWv0IfDAPxDdjP4CFM1hVI5PrdsaopZVlvULjBNEe5I mF23RVdPlrabhG6c6QHvC5UMGEWazS66sJRM7LojvwyISfDv4PDXOiRIT2L8KTDmI38V hQ2SQvB+1DMu7XiA12+FbMlFduOyoyCugJ/nxqHwhuiSAfqlHkdSCpkwNEJTHIyQXbcv 9Xhg== X-Gm-Message-State: AOJu0YxSd60EeYZ7Hkpt+dhP0oHXAaF5tupubSKL61GMgOS9SPLpO0AH j/0CGbm2jCw+AMtsr6fMN2vaAfUXeS/WjRAVLpbyHjIMKQL1thJZEIzeITK+5PfNpSzL67vkevV 0OE05q1gC1IwKLgwAZYUlqMv5pXeBZa2W23bUsRlLw30QCpzzvKXBhOODZDVCG+w/O1ZXZuI= X-Google-Smtp-Source: AGHT+IHV7SMIXl/z2ZcUCI9wh8uElpYjP827jcLFnNhWQLUNorHifjF1jTcRD63C6a9rfv1vjhH5LttK/Cqh X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a25:4081:0:b0:d10:5b67:843c with SMTP id n123-20020a254081000000b00d105b67843cmr96648yba.4.1695357387716; Thu, 21 Sep 2023 21:36:27 -0700 (PDT) Date: Fri, 22 Sep 2023 04:36:00 +0000 In-Reply-To: <20230922043616.19282-1-jstultz@google.com> Mime-Version: 1.0 References: <20230922043616.19282-1-jstultz@google.com> X-Mailer: git-send-email 2.42.0.515.g380fc7ccd1-goog Message-ID: <20230922043616.19282-3-jstultz@google.com> Subject: [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 , 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: 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 2.42.0.515.g380fc7ccd1-goog