From nobody Tue Sep 9 22:08:37 2025 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 7BA72C76195 for ; Mon, 27 Mar 2023 20:25:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231978AbjC0UZU (ORCPT ); Mon, 27 Mar 2023 16:25:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54576 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229912AbjC0UZO (ORCPT ); Mon, 27 Mar 2023 16:25:14 -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 0BD593AA5 for ; Mon, 27 Mar 2023 13:24:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1679948667; 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: in-reply-to:in-reply-to:references:references; bh=OyPFo4v7z/4QuNDV6N3/A+RFNemmtx8czMnE3tFUcd8=; b=QEwqzNqsC6VevxoVx/OSO9gD3wF2487FA+EjAZzuQIsvYiooo0WMaHxE3+n62WBRNuEXwE KXA6DsIscPRP7vDUOeWE8LT5zQ7c6VYmNtqvEqB2UYGScXvnQl7l/1KI7Q2rE7NYv5ElrF blEEhOr/9ccPUInGN0WXDJo1DPaMckM= 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-626-Rithe-3aNKO8GnJWYN1xow-1; Mon, 27 Mar 2023 16:24:23 -0400 X-MC-Unique: Rithe-3aNKO8GnJWYN1xow-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4C5C6884EC0; Mon, 27 Mar 2023 20:24:23 +0000 (UTC) Received: from llong.com (unknown [10.22.17.245]) by smtp.corp.redhat.com (Postfix) with ESMTP id D979B2027040; Mon, 27 Mar 2023 20:24:22 +0000 (UTC) From: Waiman Long To: Peter Zijlstra , Ingo Molnar , Will Deacon , Boqun Feng Cc: linux-kernel@vger.kernel.org Subject: [PATCH v2 2/8] locking/rwsem: Enforce queueing when HANDOFF Date: Mon, 27 Mar 2023 16:24:07 -0400 Message-Id: <20230327202413.1955856-3-longman@redhat.com> In-Reply-To: <20230327202413.1955856-1-longman@redhat.com> References: <20230327202413.1955856-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.4 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Peter Zijlstra Ensure that HANDOFF disables all spinning and stealing. Signed-off-by: Peter Zijlstra (Intel) --- kernel/locking/rwsem.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index e589f69793df..4b9e492abd59 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -468,7 +468,12 @@ static void rwsem_mark_wake(struct rw_semaphore *sem, adjustment -=3D RWSEM_FLAG_HANDOFF; lockevent_inc(rwsem_rlock_handoff); } + /* + * With HANDOFF set for reader, we must + * terminate all spinning. + */ waiter->handoff_set =3D true; + rwsem_set_nonspinnable(sem); } =20 atomic_long_add(-adjustment, &sem->count); @@ -755,6 +760,10 @@ rwsem_spin_on_owner(struct rw_semaphore *sem) =20 owner =3D rwsem_owner_flags(sem, &flags); state =3D rwsem_owner_state(owner, flags); + + if (owner =3D=3D current) + return OWNER_NONSPINNABLE; /* Handoff granted */ + if (state !=3D OWNER_WRITER) return state; =20 --=20 2.31.1