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 X-Spam-Level: X-Spam-Status: No, score=-18.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2FAEC4361A for ; Fri, 4 Dec 2020 02:00:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 650FA2250E for ; Fri, 4 Dec 2020 02:00:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726530AbgLDCAM (ORCPT ); Thu, 3 Dec 2020 21:00:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:58129 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726028AbgLDCAL (ORCPT ); Thu, 3 Dec 2020 21:00:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607047125; 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=PcsI/8i8s21MPFmJfyYOyMMbKAfWF0mrFKbIFuaOgvo=; b=Df4qx4EQ/zdq9q4YaM+ufj9gNdpaIKwEFyCA01LRoadMfhRHkAd4fD/fif/dE7ihXurXSo ZGX82VznMTOTRyxJAoDqmE5lLq7btCqAMybciamipdl3Bhb6Mu0Ycxvi05hlT0R4vj5OCN tjFkwit01zyxiFIECZBhtISld/xXe+I= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-284-0jl4hAROO8GO_A2F9x3dJA-1; Thu, 03 Dec 2020 20:58:41 -0500 X-MC-Unique: 0jl4hAROO8GO_A2F9x3dJA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 25568107ACE4; Fri, 4 Dec 2020 01:58:39 +0000 (UTC) Received: from llong.remote.csb (ovpn-117-98.rdu2.redhat.com [10.10.117.98]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8BCD91001901; Fri, 4 Dec 2020 01:58:33 +0000 (UTC) Subject: Re: [PATCH 1/3] rwsem: Implement down_read_killable_nested To: "Eric W. Biederman" , linux-kernel@vger.kernel.org Cc: Linus Torvalds , Peter Zijlstra , Ingo Molnar , Will Deacon , Jann Horn , Vasiliy Kulikov , Al Viro , Bernd Edlinger , Oleg Nesterov , Christopher Yeoh , Cyrill Gorcunov , Sargun Dhillon , Christian Brauner , Arnd Bergmann , Arnaldo Carvalho de Melo References: <87tut2bqik.fsf@x220.int.ebiederm.org> <87o8jabqh3.fsf@x220.int.ebiederm.org> From: Waiman Long Organization: Red Hat Message-ID: Date: Thu, 3 Dec 2020 20:58:33 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <87o8jabqh3.fsf@x220.int.ebiederm.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/3/20 3:10 PM, Eric W. Biederman wrote: > In preparation for converting exec_update_mutex to a rwsem so that > multiple readers can execute in parallel and not deadlock, add > down_read_killable_nested. This is needed so that kcmp_lock > can be converted from working on a mutexes to working on rw_semaphores. > > Cc: Peter Zijlstra > Cc: Ingo Molnar > Cc: Will Deacon > Signed-off-by: Eric W. Biederman > --- > include/linux/rwsem.h | 2 ++ > kernel/locking/rwsem.c | 14 ++++++++++++++ > 2 files changed, 16 insertions(+) > > diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h > index 25e3fde85617..13021b08b2ed 100644 > --- a/include/linux/rwsem.h > +++ b/include/linux/rwsem.h > @@ -171,6 +171,7 @@ extern void downgrade_write(struct rw_semaphore *sem); > * See Documentation/locking/lockdep-design.rst for more details.) > */ > extern void down_read_nested(struct rw_semaphore *sem, int subclass); > +extern int __must_check down_read_killable_nested(struct rw_semaphore *sem, int subclass); > extern void down_write_nested(struct rw_semaphore *sem, int subclass); > extern int down_write_killable_nested(struct rw_semaphore *sem, int subclass); > extern void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest_lock); > @@ -191,6 +192,7 @@ extern void down_read_non_owner(struct rw_semaphore *sem); > extern void up_read_non_owner(struct rw_semaphore *sem); > #else > # define down_read_nested(sem, subclass) down_read(sem) > +# define down_read_killable_nested(sem, subclass) down_read_killable(sem) > # define down_write_nest_lock(sem, nest_lock) down_write(sem) > # define down_write_nested(sem, subclass) down_write(sem) > # define down_write_killable_nested(sem, subclass) down_write_killable(sem) > diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c > index f11b9bd3431d..54d11cb97551 100644 > --- a/kernel/locking/rwsem.c > +++ b/kernel/locking/rwsem.c > @@ -1605,6 +1605,20 @@ void down_read_nested(struct rw_semaphore *sem, int subclass) > } > EXPORT_SYMBOL(down_read_nested); > > +int down_read_killable_nested(struct rw_semaphore *sem, int subclass) > +{ > + might_sleep(); > + rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_); > + > + if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_killable)) { > + rwsem_release(&sem->dep_map, _RET_IP_); > + return -EINTR; > + } > + > + return 0; > +} > +EXPORT_SYMBOL(down_read_killable_nested); > + > void _down_write_nest_lock(struct rw_semaphore *sem, struct lockdep_map *nest) > { > might_sleep(); Acked-by: Waiman Long -Longman