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 622C1EB64DC for ; Mon, 10 Jul 2023 19:25:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231479AbjGJTZg (ORCPT ); Mon, 10 Jul 2023 15:25:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41202 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229538AbjGJTZ1 (ORCPT ); Mon, 10 Jul 2023 15:25:27 -0400 Received: from mail-ed1-x531.google.com (mail-ed1-x531.google.com [IPv6:2a00:1450:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 43A4DE6E for ; Mon, 10 Jul 2023 12:25:01 -0700 (PDT) Received: by mail-ed1-x531.google.com with SMTP id 4fb4d7f45d1cf-51e429e1eabso4312946a12.2 for ; Mon, 10 Jul 2023 12:25:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1689017099; x=1691609099; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=8jAJrLaj81nDh4wW1pP27vJFmY8UiJKSEaQ+/Hb04Nc=; b=hnX3o4peRysHE4PlLHbB9M+JugRMzR7VVp6giACiIXm0TS66MpvDNrmpEM20fnHH2A oSFUd0VYZ/MdWgmzGsmXue6dq2b+VMz3GxtLT1LjmN2vOJPTyB1MlJVUP4Zg1582I7Ih bvByd4d2/2KrUOhapdZ5gYfpSGWLMwWzS/Wj/NbCJxGevCFI9QeDcs9Auy4zAcVQ/Tf8 inx384WtL7/fUnA4qAcq/gmiQWcOE2I+2JT4Su/1IT5W/UTbkLOtSMHLNoEqNw2olwUV YBlaAEf7Uv05hM5H6jTxldHdo0TkB+So0trN2HA+X0Z1MAsWYaG52b6cC+vifMgd8TY2 hLeg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689017099; x=1691609099; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=8jAJrLaj81nDh4wW1pP27vJFmY8UiJKSEaQ+/Hb04Nc=; b=la9/tb9bYitJ1FN4MvdaML+FCTPS9XGzJ3P6qg6y5b6ECUoQaRoVf4gzxW6or3/oHw MRHsmt1SqE3tPk4zy/eRWRtz3UcTvMAEeIz1CZChOKj4uVnes0WxuT6jAzPTBbrPDUWj R+y2F3U2BdYXOLbYsxNeOjrX/v/+0t8Awh9wQh78PdMuZyH55bSU2KnHZzR83glE4U5u YJIAJpG8UeiyCo7Gdyl6GbCZ+oHMuEfZQLJD0ExhsCTh3dNVFX8LzOkCoFReyWRhbKVm LJXqOdWLA2Vwc6wcLG42G60CfRai99HxLi3NZWji/22f7JOME26Q5Qwyn90hh52pcuP3 7kLQ== X-Gm-Message-State: ABy/qLZSpzs3nUQ0ISlib4AMsxbvZ6DNmBAauBpda114EB1j7XD7Bop3 rpYOb/tJRV1H9QQX3Wof022XjXT+kyWbfVAr X-Google-Smtp-Source: APBJJlHwVT5frp02REiaP08Tw2FykEOwGxdLWWsPCiw5aMtj6jXyTUwf06D5IHzSoxQJfVL+VWOmXA== X-Received: by 2002:a17:906:5307:b0:993:f996:52d3 with SMTP id h7-20020a170906530700b00993f99652d3mr6394846ejo.25.1689017099074; Mon, 10 Jul 2023 12:24:59 -0700 (PDT) Received: from localhost.localdomain ([46.248.82.114]) by smtp.gmail.com with ESMTPSA id w15-20020a170906480f00b0096a6be0b66dsm110076ejq.208.2023.07.10.12.24.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Jul 2023 12:24:58 -0700 (PDT) From: Uros Bizjak To: linux-kernel@vger.kernel.org, x86@kernel.org, xen-devel@lists.xenproject.org Cc: Uros Bizjak , Peter Zijlstra , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko Subject: [PATCH 3/3] xen: Illustrate the transition to sync_try_cmpxchg Date: Mon, 10 Jul 2023 21:21:56 +0200 Message-ID: <20230710192440.47140-3-ubizjak@gmail.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230710192440.47140-1-ubizjak@gmail.com> References: <20230710192440.47140-1-ubizjak@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch illustrates the transition to sync_try_cmpxchg. It is not intended to be merged as-is. Cc: Peter Zijlstra Cc: Juergen Gross Cc: Stefano Stabellini Cc: Oleksandr Tyshchenko Signed-off-by: Uros Bizjak --- drivers/xen/events/events_fifo.c | 26 ++++++++++++-------------- drivers/xen/grant-table.c | 10 ++++------ 2 files changed, 16 insertions(+), 20 deletions(-) diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c index ad9fe51d3fb3..655775db7caf 100644 --- a/drivers/xen/events/events_fifo.c +++ b/drivers/xen/events/events_fifo.c @@ -226,21 +226,20 @@ static bool evtchn_fifo_is_masked(evtchn_port_t port) */ static bool clear_masked_cond(volatile event_word_t *word) { - event_word_t new, old, w; + event_word_t new, old; - w = *word; + old = *word; do { - if (!(w & (1 << EVTCHN_FIFO_MASKED))) + if (!(old & (1 << EVTCHN_FIFO_MASKED))) return true; - if (w & (1 << EVTCHN_FIFO_PENDING)) + if (old & (1 << EVTCHN_FIFO_PENDING)) return false; - old = w & ~(1 << EVTCHN_FIFO_BUSY); + old = old & ~(1 << EVTCHN_FIFO_BUSY); new = old & ~(1 << EVTCHN_FIFO_MASKED); - w = sync_cmpxchg(word, old, new); - } while (w != old); + } while (!sync_try_cmpxchg(word, &old, new)); return true; } @@ -259,17 +258,16 @@ static void evtchn_fifo_unmask(evtchn_port_t port) static uint32_t clear_linked(volatile event_word_t *word) { - event_word_t new, old, w; + event_word_t new, old; - w = *word; + old = *word; do { - old = w; - new = (w & ~((1 << EVTCHN_FIFO_LINKED) - | EVTCHN_FIFO_LINK_MASK)); - } while ((w = sync_cmpxchg(word, old, new)) != old); + new = (old & ~((1 << EVTCHN_FIFO_LINKED) + | EVTCHN_FIFO_LINK_MASK)); + } while (!sync_try_cmpxchg(word, &old, new)); - return w & EVTCHN_FIFO_LINK_MASK; + return old & EVTCHN_FIFO_LINK_MASK; } static void consume_one_event(unsigned cpu, struct evtchn_loop_ctrl *ctrl, diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index e1ec725c2819..211d083d4fbe 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -427,16 +427,14 @@ EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access); static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref) { - u16 flags, nflags; - u16 *pflags; + u16 *pflags = &gnttab_shared.v1[ref].flags; + u16 flags; - pflags = &gnttab_shared.v1[ref].flags; - nflags = *pflags; + flags = *pflags; do { - flags = nflags; if (flags & (GTF_reading|GTF_writing)) return 0; - } while ((nflags = sync_cmpxchg(pflags, flags, 0)) != flags); + } while (!sync_try_cmpxchg(pflags, &flags, 0)); return 1; } -- 2.41.0