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 62031EB64D9 for ; Fri, 7 Jul 2023 13:10:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231950AbjGGNKF (ORCPT ); Fri, 7 Jul 2023 09:10:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229458AbjGGNKE (ORCPT ); Fri, 7 Jul 2023 09:10:04 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5EDBB1737 for ; Fri, 7 Jul 2023 06:09:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688735356; 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: in-reply-to:in-reply-to:references:references; bh=EggKBwzUqnd+oemu+sOZluKy6hIEM/b0yh51QTFGBVA=; b=Vu5A2r9xQsaOF3bzsQQjPmrzgyLJfYhJIQHiqBBh+8zBi7ufMn9nAr/KCcwGoxA5O59bR+ yyitUqZp30eNqjaJOesTlebZCuZmQEKStFUiEQeIrKg/92l6t/dbPMH1jSEjAGZao770mi hlV2hIu5HkJ7w714MZ6+aUiFNHpaCM0= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-28-b-m9TsE5N2q0OmSuYaprgw-1; Fri, 07 Jul 2023 09:09:15 -0400 X-MC-Unique: b-m9TsE5N2q0OmSuYaprgw-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 64ECB1044591; Fri, 7 Jul 2023 13:09:14 +0000 (UTC) Received: from [10.22.34.12] (unknown [10.22.34.12]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9A78C1121330; Fri, 7 Jul 2023 13:09:13 +0000 (UTC) Message-ID: Date: Fri, 7 Jul 2023 09:09:13 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH] refscale: Fix use of uninitalized wait_queue_head_t Content-Language: en-US To: "Zhuo, Qiuxu" , "Paul E. McKenney" , Davidlohr Bueso , Josh Triplett , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Boqun Feng , Zqiang Cc: "rcu@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20230707000117.2371697-1-longman@redhat.com> From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/7/23 03:27, Zhuo, Qiuxu wrote: >> From: Waiman Long >> ... >> Subject: [PATCH] refscale: Fix use of uninitalized wait_queue_head_t >> >> It was found that running the refscale test might sometimes crash the kernel >> with the following error: >> >> [ 8569.952896] BUG: unable to handle page fault for address: ffffffffffffffe8 >> [ 8569.952900] #PF: supervisor read access in kernel mode [ 8569.952902] >> #PF: error_code(0x0000) - not-present page [ 8569.952904] PGD c4b048067 >> P4D c4b049067 PUD c4b04b067 PMD 0 [ 8569.952910] Oops: 0000 [#1] >> PREEMPT_RT SMP NOPTI [ 8569.952916] Hardware name: Dell Inc. >> PowerEdge R750/0WMWCR, BIOS 1.2.4 05/28/2021 [ 8569.952917] RIP: >> 0010:prepare_to_wait_event+0x101/0x190 >> : >> [ 8569.952940] Call Trace: >> [ 8569.952941] >> [ 8569.952944] ref_scale_reader+0x380/0x4a0 [refscale] [ 8569.952959] >> kthread+0x10e/0x130 [ 8569.952966] ret_from_fork+0x1f/0x30 >> [ 8569.952973] >> >> This is likely caused by the fact that init_waitqueue_head() is called after the >> ref_scale_reader kthread is created. So the kthread may try to use the >> waitqueue head before it is properly initialized. Fix this by initializing the >> waitqueue head first before kthread creation. >> >> Fixes: 653ed64b01dc ("refperf: Add a test to measure performance of read- >> side synchronization") >> Signed-off-by: Waiman Long >> --- >> kernel/rcu/refscale.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index >> 1970ce5f22d4..e365d6f8c139 100644 >> --- a/kernel/rcu/refscale.c >> +++ b/kernel/rcu/refscale.c >> @@ -1107,12 +1107,11 @@ ref_scale_init(void) >> VERBOSE_SCALEOUT("Starting %d reader threads", nreaders); >> >> for (i = 0; i < nreaders; i++) { >> + init_waitqueue_head(&(reader_tasks[i].wq)); > Running checkpatch.pl tool with the " --strict" option, it complained that > "CHECK: Unnecessary parentheses around reader_tasks[i].wq". > I know that you just moved the code position. The tool should have > complained the original code. 😊 > > Other than that, this patch LGTM. > > Reviewed-by: Qiuxu Zhuo > > Thanks! > -Qiuxu Thanks for the review. I will do --strict test next time. Cheers, Longman > >> firsterr = torture_create_kthread(ref_scale_reader, (void *)i, >> reader_tasks[i].task); >> if (torture_init_error(firsterr)) >> goto unwind; >> - >> - init_waitqueue_head(&(reader_tasks[i].wq)); >> } >> >> // Main Task >> -- >> 2.31.1