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 79CD4C433EF for ; Thu, 2 Jun 2022 20:33:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238663AbiFBUdK (ORCPT ); Thu, 2 Jun 2022 16:33:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239029AbiFBUcp (ORCPT ); Thu, 2 Jun 2022 16:32:45 -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 0C5D36256 for ; Thu, 2 Jun 2022 13:32:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1654201963; 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=sn8GQc5Tco14Vhb/wDmW6cQmzJEdQ2zBkHzzT9RyDZE=; b=HY34Egl1+GHFHMqUh5Vh6oEzUotJCh6QunhSahoAFKw+UCP0HezJG0dem0k7DD/nlKs5mE 0gZAKFPw1zZrCX+c0/i+0t7/PFaTdXuPAxYIjCwAkxejbQ+bScnsjzdl2wzShCw3aPsLZT PROoeqGUBmToFGyP9XqwnYUH+7h+1PM= 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-225-lS5pDRv5OVea_ihGxqlWJQ-1; Thu, 02 Jun 2022 16:32:38 -0400 X-MC-Unique: lS5pDRv5OVea_ihGxqlWJQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A17B2380451B; Thu, 2 Jun 2022 20:32:37 +0000 (UTC) Received: from jlaw-desktop.redhat.com (unknown [10.22.8.184]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3B7661121314; Thu, 2 Jun 2022 20:32:37 +0000 (UTC) From: Joe Lawrence To: live-patching@vger.kernel.org Cc: Joe Lawrence , Miroslav Benes , Petr Mladek , Yannick Cote Subject: [PATCH v2] selftests/livepatch: better synchronize test_klp_callbacks_busy Date: Thu, 2 Jun 2022 16:32:33 -0400 Message-Id: <20220602203233.979681-1-joe.lawrence@redhat.com> MIME-Version: 1.0 Content-type: text/plain Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 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 Reviewed-by: Petr Mladek --- lib/livepatch/test_klp_callbacks_busy.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/lib/livepatch/test_klp_callbacks_busy.c b/lib/livepatch/test_klp_callbacks_busy.c index 7ac845f65be5..133929e0ce8f 100644 --- a/lib/livepatch/test_klp_callbacks_busy.c +++ b/lib/livepatch/test_klp_callbacks_busy.c @@ -16,10 +16,12 @@ 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) { pr_info("%s enter\n", __func__); + complete(&busymod_work_started); while (READ_ONCE(block_transition)) { /* @@ -37,6 +39,12 @@ static int test_klp_callbacks_busy_init(void) pr_info("%s\n", __func__); schedule_work(&work); + /* + * To synchronize kernel messages, hold the init function from + * exiting until the work function's entry message has printed. + */ + wait_for_completion(&busymod_work_started); + if (!block_transition) { /* * Serialize output: print all messages from the work -- 2.26.3