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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 D8C97C433E0 for ; Tue, 30 Jun 2020 17:39:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B27F120853 for ; Tue, 30 Jun 2020 17:39:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593538740; bh=9ta772X0LhIYPaLbgcx1JUvYo6hXV5XVnuUlAptrUOU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xPRfMPK/On7NTauuyVVgdvrqVibIJem9ADfhCr0CL1c+VH25W3slTo8TDMlu9ATT0 f224/ugVzafc6Xqea26zoka4XTyGHlU8xh7dXWaBk8snr4EN9tBjL8dYfSmxVk18Ju 1sgmY501rwJaf0ZfxTpZTjm8Rn1KB9tXB/+0R3Dk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390479AbgF3Ri5 (ORCPT ); Tue, 30 Jun 2020 13:38:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:52262 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388439AbgF3Riz (ORCPT ); Tue, 30 Jun 2020 13:38:55 -0400 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 218CE208D5; Tue, 30 Jun 2020 17:38:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593538734; bh=9ta772X0LhIYPaLbgcx1JUvYo6hXV5XVnuUlAptrUOU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0q+Ziga1tPlskSYQCOixoO6Z7LOXNz3B6jLLCGqxp/nOY1c+yQMi4dmX9JM37+9y0 ZK9XtOGvfQUWp0T7YRsp5zuJSE8D4Xcg5v8WcxEy/7r+jxhV6fRVjnfN6L3KkrZKkU ebDLdVemnERh2RnFrQjwFEjyJUmdx4Rab8Jh0TpI= From: Will Deacon To: linux-kernel@vger.kernel.org Cc: Will Deacon , Sami Tolvanen , Nick Desaulniers , Kees Cook , Marco Elver , "Paul E. McKenney" , Josh Triplett , Matt Turner , Ivan Kokshaysky , Richard Henderson , Peter Zijlstra , Alan Stern , "Michael S. Tsirkin" , Jason Wang , Arnd Bergmann , Boqun Feng , Catalin Marinas , Mark Rutland , linux-arm-kernel@lists.infradead.org, linux-alpha@vger.kernel.org, virtualization@lists.linux-foundation.org, kernel-team@android.com Subject: [PATCH 17/18] arm64: alternatives: Remove READ_ONCE() usage during patch operation Date: Tue, 30 Jun 2020 18:37:33 +0100 Message-Id: <20200630173734.14057-18-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200630173734.14057-1-will@kernel.org> References: <20200630173734.14057-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In preparation for patching the internals of READ_ONCE() itself, replace its usage on the alternatives patching patch with a volatile variable instead. Signed-off-by: Will Deacon --- arch/arm64/kernel/alternative.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c index d1757ef1b1e7..87bca8d44084 100644 --- a/arch/arm64/kernel/alternative.c +++ b/arch/arm64/kernel/alternative.c @@ -21,7 +21,8 @@ #define ALT_ORIG_PTR(a) __ALT_PTR(a, orig_offset) #define ALT_REPL_PTR(a) __ALT_PTR(a, alt_offset) -static int all_alternatives_applied; +/* Volatile, as we may be patching the guts of READ_ONCE() */ +static volatile int all_alternatives_applied; static DECLARE_BITMAP(applied_alternatives, ARM64_NCAPS); @@ -217,7 +218,7 @@ static int __apply_alternatives_multi_stop(void *unused) /* We always have a CPU 0 at this point (__init) */ if (smp_processor_id()) { - while (!READ_ONCE(all_alternatives_applied)) + while (!all_alternatives_applied) cpu_relax(); isb(); } else { @@ -229,7 +230,7 @@ static int __apply_alternatives_multi_stop(void *unused) BUG_ON(all_alternatives_applied); __apply_alternatives(®ion, false, remaining_capabilities); /* Barriers provided by the cache flushing */ - WRITE_ONCE(all_alternatives_applied, 1); + all_alternatives_applied = 1; } return 0; -- 2.27.0.212.ge8ba1cc988-goog