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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 F3553C10F27 for ; Tue, 10 Mar 2020 21:22:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E46E9205F4 for ; Tue, 10 Mar 2020 21:22:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727573AbgCJVWC (ORCPT ); Tue, 10 Mar 2020 17:22:02 -0400 Received: from mx2.suse.de ([195.135.220.15]:56302 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726268AbgCJVWA (ORCPT ); Tue, 10 Mar 2020 17:22:00 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 9F294AFDF; Tue, 10 Mar 2020 21:21:58 +0000 (UTC) From: NeilBrown To: Jeff Layton , yangerkun , Linus Torvalds Date: Wed, 11 Mar 2020 08:21:49 +1100 Cc: kernel test robot , LKML , lkp@lists.01.org, Bruce Fields , Al Viro Subject: Re: [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression In-Reply-To: References: <20200308140314.GQ5972@shao2-debian> <34355c4fe6c3968b1f619c60d5ff2ca11a313096.camel@kernel.org> <1bfba96b4bf0d3ca9a18a2bced3ef3a2a7b44dad.camel@kernel.org> <87blp5urwq.fsf@notabene.neil.brown.name> <41c83d34ae4c166f48e7969b2b71e43a0f69028d.camel@kernel.org> <923487db2c9396c79f8e8dd4f846b2b1762635c8.camel@kernel.org> <36c58a6d07b67aac751fca27a4938dc1759d9267.camel@kernel.org> <878sk7vs8q.fsf@notabene.neil.brown.name> Message-ID: <875zfbvrbm.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Tue, Mar 10 2020, Jeff Layton wrote: >> @@ -735,11 +723,13 @@ static void __locks_wake_up_blocks(struct file_loc= k *blocker) >>=20=20 >> waiter =3D list_first_entry(&blocker->fl_blocked_requests, >> struct file_lock, fl_blocked_member); >> - __locks_delete_block(waiter); >> + locks_delete_global_blocked(waiter); >> + waiter->fl_blocker =3D NULL; >> if (waiter->fl_lmops && waiter->fl_lmops->lm_notify) >> waiter->fl_lmops->lm_notify(waiter); >> else >> wake_up(&waiter->fl_wait); >> + list_del_init(&waiter->fl_blocked_member); > > Are you sure you don't need a memory barrier here? Could the > list_del_init be hoisted just above the if condition? > A compiler barrier() is probably justified. Memory barriers delay reads and expedite writes so they cannot be needed. wake_up(&waiter->fl_wait); + /* The list_del_init() must not be visible before the + * wake_up completes, the the waiter can then be freed. + */ + barrier(); + list_del_init(&waiter->fl_blocked_member); Thanks, NeilBrown --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEG8Yp69OQ2HB7X0l6Oeye3VZigbkFAl5oBO0ACgkQOeye3VZi gblwqQ/8DkoZJyjuip/ioeNV4RJRreBlvckVZvhMWegAEcWtiVd5cIxwwz8R4C/Q Wjqpyxw9g2jzlhbwNfjQwgQqVyWppGrzjhWlIDD5Js6nE8BKTBFtaWpcFsfZ6CX+ xieFoX0DIVAqqqJZPY2GaJZ11PUtJMHmr+/nDz2IdQNEcZuu34V1z+kTFzYyXevm 4lEy/8e5c16/lRID0fB4kk3RkcrM3DMnvONExpW2jqK0MrDMoTkxbLhhtMKONj0j qDYCe7sV7+h9dxGA5WFWxvbt6l4n6epnNa5pKqihLtFqi85jGTygbca3V8W8YDM6 inrX9L+EduuK0VBP21sWc0k1YZTF3xCt+uVTLM/qROevkxivD6vWCB2XdAqNbnoj raxEz15GEoMqAUlaPQ73hpvMfeAaeXVEm9gsgp7LjzoyQzL7F6rk5xQ/ccRo4cK2 zEoGnAt9kXQpobSfjnOELoFbzEFshSxzwQuEzmeh8fe7z84qjMVBl2kJOcL2XJ0N dv2jiyG46DPl1ALm9EAVv4qlcwmOe4vklq087STWgGbAJTlzj+Q6SayXyOAwdzK+ RRxyvjEcPfS0xivpE2l0FkU/zjcg+A1HkSG94KPEP4xjLalfevU68H3BoSCfuGr2 PueecWCIamfD9nVunUqyawXWxdPISUKNrgq1sqQ2J8exnpUqMIU= =ZHtk -----END PGP SIGNATURE----- --=-=-=--