From nobody Sat Feb 7 22:55:19 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 986D4EB64DD for ; Fri, 7 Jul 2023 00:02:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231965AbjGGACY (ORCPT ); Thu, 6 Jul 2023 20:02:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50028 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229748AbjGGACW (ORCPT ); Thu, 6 Jul 2023 20:02:22 -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 2B5B71997 for ; Thu, 6 Jul 2023 17:01:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688688095; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=td6ndgPu8UyiPBmx1pFKVKko26hP20xZBaFgi1+OAqA=; b=daoVDoGVcufBPdK8wj3l9/RADR3e/F5cysgeTHVmr6WQWwpPxMl2Gavt5v8FM93h8OMBN8 uj9Qeue8QgPeodOe8ppq862NUszC0/iWDPncrOwBYye0L9UckRp/Gv+/sxgQDH8wsIvmzY W4bP//xbiMiwey9kFWP+TQBXkc2Rvdw= 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-374-R49XuHfEOle7pJJ01ySK9w-1; Thu, 06 Jul 2023 20:01:27 -0400 X-MC-Unique: R49XuHfEOle7pJJ01ySK9w-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 81647185A791; Fri, 7 Jul 2023 00:01:26 +0000 (UTC) Received: from llong.com (unknown [10.22.9.44]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5F4522166B25; Fri, 7 Jul 2023 00:01:25 +0000 (UTC) From: Waiman Long To: "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, Waiman Long Subject: [PATCH] refscale: Fix use of uninitalized wait_queue_head_t Date: Thu, 6 Jul 2023 20:01:17 -0400 Message-Id: <20230707000117.2371697-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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: ffffffffffffff= e8 [ 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 0= 5/28/2021 [ 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-si= de synchronization") Signed-off-by: Waiman Long Acked-by: Joel Fernandes (Google) Reviewed-by: Davidlohr Bueso --- 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); =20 for (i =3D 0; i < nreaders; i++) { + init_waitqueue_head(&(reader_tasks[i].wq)); firsterr =3D 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)); } =20 // Main Task --=20 2.31.1