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 D1053C433F5 for ; Wed, 18 May 2022 17:34:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240921AbiERRej (ORCPT ); Wed, 18 May 2022 13:34:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55480 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240955AbiERRei (ORCPT ); Wed, 18 May 2022 13:34:38 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 529BDBCE9C for ; Wed, 18 May 2022 10:34:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652895270; h=from:from: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; bh=k7oz4e4aJMs7N3/jTHMdgyAk86Qj1FfimALtt+HOfaM=; b=e9kpU+wKETcynWaCM5MAy2shjZICMMTm9LqlierTJQKvDbn6WTQ/oghBDV5d2hLXXwjkX0 mTu1okNzjDlZSlawW260+BhcUyXcMwOsw4bO89hSnPOLVyzpalXufT/N6MJy4uuoLbTlOy JPIfGuA17egewKzhC4CDg5Pspvm2ilk= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-25-G-dRTGqiNbucaO0_1zwP5g-1; Wed, 18 May 2022 13:34:27 -0400 X-MC-Unique: G-dRTGqiNbucaO0_1zwP5g-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 80BA83C60520; Wed, 18 May 2022 17:34:26 +0000 (UTC) Received: from jlaw-desktop.redhat.com (unknown [10.22.16.62]) by smtp.corp.redhat.com (Postfix) with ESMTP id 25C5240C1421; Wed, 18 May 2022 17:34:26 +0000 (UTC) From: Joe Lawrence To: live-patching@vger.kernel.org Cc: Joe Lawrence , Miroslav Benes , Petr Mladek , Yannick Cote Subject: [PATCH] selftests/livepatch: better synchronize test_klp_callbacks_busy Date: Wed, 18 May 2022 13:34:24 -0400 Message-Id: <20220518173424.911649-1-joe.lawrence@redhat.com> MIME-Version: 1.0 Content-type: text/plain Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org The test_klp_callbacks_busy module conditionally blocks a future livepatch transition by busy waiting inside its workqueue function, busymod_work_func(). After scheduling this work, a test livepatch is loaded, introducing the transition under test. Both events are marked in the kernel log for later verification, but there is no synchronization to ensure that busymod_work_func() logs its function entry message before subsequent selftest commands log their own messages. This can lead to a rare test failure due to unexpected ordering like: --- expected +++ result @@ -1,7 +1,7 @@ % modprobe test_klp_callbacks_busy block_transition=Y test_klp_callbacks_busy: test_klp_callbacks_busy_init -test_klp_callbacks_busy: busymod_work_func enter % modprobe test_klp_callbacks_demo +test_klp_callbacks_busy: busymod_work_func enter livepatch: enabling patch 'test_klp_callbacks_demo' livepatch: 'test_klp_callbacks_demo': initializing patching transition test_klp_callbacks_demo: pre_patch_callback: vmlinux Force the module init function to wait until busymod_work_func() has started (and logged its message), before exiting to the next selftest steps. Fixes: 547840bd5ae5 ("selftests/livepatch: simplify test-klp-callbacks busy target tests") Signed-off-by: Joe Lawrence --- Hi Petr, I remember you discouraged against a completion variable the first time around [1], but is there any better way with the workqueue API to ensure our "enter" message gets logged first? Or should we just drop the msg altogether to avoid the situation? I don't think it's absolutely necessary for the tests. [1] https://lore.kernel.org/live-patching/20200602081654.GI27273@linux-b0ei/ lib/livepatch/test_klp_callbacks_busy.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/lib/livepatch/test_klp_callbacks_busy.c b/lib/livepatch/test_klp_callbacks_busy.c index 7ac845f65be5..eb502b2bb3ef 100644 --- a/lib/livepatch/test_klp_callbacks_busy.c +++ b/lib/livepatch/test_klp_callbacks_busy.c @@ -16,10 +16,16 @@ MODULE_PARM_DESC(block_transition, "block_transition (default=false)"); static void busymod_work_func(struct work_struct *work); static DECLARE_WORK(work, busymod_work_func); +static DECLARE_COMPLETION(busymod_work_started); static void busymod_work_func(struct work_struct *work) { + /* + * Hold the init function from exiting until we've started and + * announced our appearence in the kernel log. + */ pr_info("%s enter\n", __func__); + complete(&busymod_work_started); while (READ_ONCE(block_transition)) { /* @@ -36,6 +42,7 @@ static int test_klp_callbacks_busy_init(void) { pr_info("%s\n", __func__); schedule_work(&work); + wait_for_completion(&busymod_work_started); if (!block_transition) { /* -- 2.26.3