From nobody Sun Feb 8 11:44:53 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 A2D68C001B0 for ; Tue, 8 Aug 2023 18:40:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233256AbjHHSkF (ORCPT ); Tue, 8 Aug 2023 14:40:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57618 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232846AbjHHSjn (ORCPT ); Tue, 8 Aug 2023 14:39:43 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 966A014E747 for ; Tue, 8 Aug 2023 10:04:26 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-5897d05e878so7609027b3.3 for ; Tue, 08 Aug 2023 10:04:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1691514263; x=1692119063; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=6Pj22MKmr8XIhh1K0aihl/wpxs9R/qGJHCHsUaf0qEA=; b=s0xWzXU70VZY4/sag/71nAGjSBw0VTsldkRXrQv6hNF6rmShd40JQtJnRdQyZ+iqTK 5KBQnevbciD9hRputkVCUki0nuPPo4YuQTp9SNDBBj+h3SW0+ck2qUTTiLIzA/wkNxvI cV27wWiHSGKysqfzCqw0NyAIKFMx5eNV1ALBXhVGzL6BXLdu5Zw1zDJeXqHrdxizGWSK qBqsnCIZn1yJYMDNyqqnMwg2RLRE2tUousQzZENCNcI/5HzaxlTYgjrN8ZCGr7mXQBXv 8xw+9R2b353EPTq7m6N0FNmy65uljEbsKpFSHBeTpHnlHUNjJaOGLe/rR6dT+yEB71Br BBHA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1691514263; x=1692119063; 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=6Pj22MKmr8XIhh1K0aihl/wpxs9R/qGJHCHsUaf0qEA=; b=bvsCN8+ZXGxcO/QkYZs3phxJA6p1IYz50mWqRr43Mqk7QDkqrDSNdRIz6/F9SMKw/N V6X1bjUt0C7B8n0mog0hbHvoxQYJl/tEkDQyOr0DYYjhgSwesTPdlnxct7SjpvGu0Ey6 CkXCrHEGQPZwltuSeL+nKWNOENU31IcP8Wamow3gTF1MGIFkNzhPJFpKVWMMfR3inQDD R2FJjoImCX93dqJrjYU5/B9IpqJv/mw57NoFBZbtxK5wWP7Onc4FK5aZL1n+lNbuSnYU 4h9lv4olWH/sb56n0KbWDKgsCnXYPRRKNLJI+0+/Nwp7k0g0lruFSlmILhA9lL4L5uJp tXvQ== X-Gm-Message-State: AOJu0YwcCKkrR7YU/PNXsFkPSE99CA4CZxvZQUUgHNd3Jt9SvP9+r/yU r7eQAPe7iaBT/DBFIXz2HMIZqXsKsgOKC6QdW8EjHwbQ83xWklcIAyt/3wreZuHjL2epw9jba4u 55FV/uvE8+zN7c/7XjRf10Bc0Dr7mIhDco13G5omxW9F6dKU61ExuJ2q9uCpHP9QCl+Spq0U= X-Google-Smtp-Source: AGHT+IHqx2QI+7pJSjzr9uHQXPaw5pVfN0pf1+WRluhAo+loAGS0f/4XjbvkD6Leg6ztTpG/cWZBXZsgpUxj X-Received: from jstultz-noogler2.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:600]) (user=jstultz job=sendgmr) by 2002:a63:770c:0:b0:551:eb6:1ea6 with SMTP id s12-20020a63770c000000b005510eb61ea6mr48746pgc.10.1691476027531; Mon, 07 Aug 2023 23:27:07 -0700 (PDT) Date: Tue, 8 Aug 2023 06:26:43 +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: <20230808062658.391595-4-jstultz@google.com> Subject: [RFC][PATCH 3/3] test-ww_mutex: Make sure we bail out instead of livelock 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" I've seen what appears to be livelocks in the stress_inorder_work() function, and looking at the code it is clear we can have a case where we continually retry acquiring the locks and never check to see if we have passed the specified timeout. This patch reworks that function so we always check the timeout before iterating through the loop again. I believe others may have hit this previously here: https://lore.kernel.org/lkml/895ef450-4fb3-5d29-a6ad-790657106a5a@intel.com/ 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 Reported-by: Li Zhijian Link: https://lore.kernel.org/lkml/895ef450-4fb3-5d29-a6ad-790657106a5a@int= el.com/ Signed-off-by: John Stultz --- kernel/locking/test-ww_mutex.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c index 358d66150426..78719e1ef1b1 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -465,17 +465,18 @@ static void stress_inorder_work(struct work_struct *w= ork) ww_mutex_unlock(&locks[order[n]]); =20 if (err =3D=3D -EDEADLK) { - ww_mutex_lock_slow(&locks[order[contended]], &ctx); - goto retry; + if (!time_after(jiffies, stress->timeout)) { + ww_mutex_lock_slow(&locks[order[contended]], &ctx); + goto retry; + } } =20 + ww_acquire_fini(&ctx); if (err) { pr_err_once("stress (%s) failed with %d\n", __func__, err); break; } - - ww_acquire_fini(&ctx); } while (!time_after(jiffies, stress->timeout)); =20 kfree(order); --=20 2.41.0.640.ga95def55d0-goog