From nobody Wed Dec 31 06:37:46 2025 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 CDEBAC4167B for ; Mon, 6 Nov 2023 23:08:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233536AbjKFXIF (ORCPT ); Mon, 6 Nov 2023 18:08:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233512AbjKFXHc (ORCPT ); Mon, 6 Nov 2023 18:07:32 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4342210F3; Mon, 6 Nov 2023 15:07:29 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EADB8C433C7; Mon, 6 Nov 2023 23:07:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699312048; bh=N6GHA1pxyKC1p46ueFgQb+Ovp4j2adx/8SQF407SWt0=; h=From:To:Cc:Subject:Date:From; b=l/4YXCVUV5BSaA5Wa7s+89WtCB8L9nUbR996FBU3iZQIEeUfkVqDIsj+7auI9oXGF BfGZXxE/wVO0DeGBupiaDm82n4BCLHTYIfLFTuEzJ8K9Sbzd4Q/ZsK3s96b2WdCMpl apmdYmkqRmko8iHO20/88BXj6nN7LYFHCj7lWxXB/7TGp/w/bZjHnlHbCeoWfk33iU LdxJ11n/7YRMmb8uSdvy5mofxfpxQ4c7hr4ZlUm5MsUj0Aq/RWCgQxWnKy4erZgQHr k86D3IR6YJXnKQuTKs5pUEJR8+dLwXeDf3FVVX6LTs/78rM3kgpL40EuSi0Hl37ipN 07PYEI4a2TL6Q== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: John Stultz , Ingo Molnar , Sasha Levin , peterz@infradead.org, mingo@redhat.com, will@kernel.org Subject: [PATCH AUTOSEL 4.19] locking/ww_mutex/test: Fix potential workqueue corruption Date: Mon, 6 Nov 2023 18:07:25 -0500 Message-ID: <20231106230726.3734650-1-sashal@kernel.org> X-Mailer: git-send-email 2.42.0 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 4.19.297 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: John Stultz [ Upstream commit bccdd808902f8c677317cec47c306e42b93b849e ] 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 Signed-off-by: Sasha Levin --- 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 65a3b7e55b9fc..4fd05d9d5d6d1 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -439,7 +439,6 @@ 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 { @@ -504,7 +503,6 @@ 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) @@ -525,8 +523,6 @@ static void stress_one_work(struct work_struct *work) break; } } while (!time_after(jiffies, stress->timeout)); - - kfree(stress); } =20 #define STRESS_INORDER BIT(0) @@ -537,15 +533,24 @@ 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); @@ -569,9 +574,7 @@ 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; @@ -586,6 +589,7 @@ 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