From nobody Wed Sep 10 08:44:14 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 B0780C61DA4 for ; Thu, 23 Feb 2023 12:35:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233999AbjBWMfC (ORCPT ); Thu, 23 Feb 2023 07:35:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58254 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233896AbjBWMes (ORCPT ); Thu, 23 Feb 2023 07:34:48 -0500 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 77745532AC for ; Thu, 23 Feb 2023 04:34:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=0TS8nXz+u1sbnPtO4cPWraWjlrBkSRepEXgG/CH9vjk=; b=mN5vdRVpmTtTwyuN2DIFDauxqj 1o3qoMLZfcsM6maEP16gO+DSlQfS5ptl7EPmIPsPda4yq4sG369icdDjiUuaUYF+QIocsyOzMyZ96 6dklfwYDxpDR8zBjS9UOctta8RTPWdySmOX3yEYMR95FsXskw1nMviCP+PMybek5DF/0X+IpyocRP EyJH3qRjjaqcU8T1POIFwSGm8JuQrGsS7bSkVdiEvvyFtlhgXi/QeKMLOwtL1fLj1sJkSj49eoVk7 Rq1JOT1cSqa/rkEd/K5MZ6L/4ug8N9I7xuy1skmNaJ7C5XLPffjET0T2Qhy5F0derdG4e41Uwu9TM wghnXc8w==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.96 #2 (Red Hat Linux)) id 1pVAo0-00CuV7-0x; Thu, 23 Feb 2023 12:34:36 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id D174E30067B; Thu, 23 Feb 2023 13:34:35 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id B84AE2C86FE03; Thu, 23 Feb 2023 13:34:35 +0100 (CET) Message-ID: <20230223123319.428168721@infradead.org> User-Agent: quilt/0.66 Date: Thu, 23 Feb 2023 13:26:44 +0100 From: Peter Zijlstra To: longman@redhat.com, mingo@redhat.com, will@kernel.org Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, boqun.feng@gmail.com Subject: [PATCH 2/6] locking/rwsem: Enforce queueing when HANDOFF References: <20230223122642.491637862@infradead.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Ensure that HANDOFF disables all spinning and stealing. Signed-off-by: Peter Zijlstra (Intel) --- kernel/locking/rwsem.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -468,7 +468,12 @@ static void rwsem_mark_wake(struct rw_se 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 =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;