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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6629C433FE for ; Mon, 28 Nov 2022 06:17:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229790AbiK1GRN (ORCPT ); Mon, 28 Nov 2022 01:17:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33098 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229603AbiK1GRL (ORCPT ); Mon, 28 Nov 2022 01:17:11 -0500 Received: from out30-42.freemail.mail.aliyun.com (out30-42.freemail.mail.aliyun.com [115.124.30.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85F2311174 for ; Sun, 27 Nov 2022 22:17:09 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R181e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045170;MF=xuanzhuo@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0VVoRcX4_1669616225; Received: from localhost(mailfrom:xuanzhuo@linux.alibaba.com fp:SMTPD_---0VVoRcX4_1669616225) by smtp.aliyun-inc.com; Mon, 28 Nov 2022 14:17:06 +0800 Message-ID: <1669616200.943005-3-xuanzhuo@linux.alibaba.com> Subject: Re: [PATCH 2/2] tools/virtio: remove smp_read_barrier_depends() Date: Mon, 28 Nov 2022 14:16:40 +0800 From: Xuan Zhuo To: Davidlohr Bueso Cc: dave@stgolabs.net, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, mst@redhat.com References: <20221128034347.990-1-dave@stgolabs.net> <20221128034347.990-3-dave@stgolabs.net> In-Reply-To: <20221128034347.990-3-dave@stgolabs.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 27 Nov 2022 19:43:47 -0800, Davidlohr Bueso wrote: > This gets rid of the last references to smp_read_barrier_depends() > which for the kernel side was removed in v5.9. The serialization > required for Alpha is done inside READ_ONCE() instead of having > users deal with it. Simply use a full barrier, the architecture > does not have rmb in the first place. > > Signed-off-by: Davidlohr Bueso Reviewed-by: Xuan Zhuo > --- > tools/virtio/ringtest/main.h | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) > > diff --git a/tools/virtio/ringtest/main.h b/tools/virtio/ringtest/main.h > index 9ed09caa659e..b68920d52750 100644 > --- a/tools/virtio/ringtest/main.h > +++ b/tools/virtio/ringtest/main.h > @@ -140,12 +140,6 @@ static inline void busy_wait(void) > #define smp_wmb() smp_release() > #endif > > -#ifdef __alpha__ > -#define smp_read_barrier_depends() smp_acquire() > -#else > -#define smp_read_barrier_depends() do {} while(0) > -#endif > - > static __always_inline > void __read_once_size(const volatile void *p, void *res, int size) > { > @@ -175,13 +169,22 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s > } > } > > +#ifdef __alpha__ > #define READ_ONCE(x) \ > ({ \ > union { typeof(x) __val; char __c[1]; } __u; \ > __read_once_size(&(x), __u.__c, sizeof(x)); \ > - smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \ > + smp_mb(); /* Enforce dependency ordering from x */ \ > __u.__val; \ > }) > +#else > +#define READ_ONCE(x) \ > +({ \ > + union { typeof(x) __val; char __c[1]; } __u; \ > + __read_once_size(&(x), __u.__c, sizeof(x)); \ > + __u.__val; \ > +}) > +#endif > > #define WRITE_ONCE(x, val) \ > ({ \ > -- > 2.38.1 > > _______________________________________________ > Virtualization mailing list > Virtualization@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/virtualization