From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755667AbdJIXJG (ORCPT ); Mon, 9 Oct 2017 19:09:06 -0400 Received: from mga02.intel.com ([134.134.136.20]:40508 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754416AbdJIXJF (ORCPT ); Mon, 9 Oct 2017 19:09:05 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.42,501,1500966000"; d="scan'208";a="1228931024" Reply-To: thor.thayer@linux.intel.com Subject: Re: [PATCH 02/13] EDAC, altera: kill off ACCESS_ONCE() To: Mark Rutland , linux-kernel@vger.kernel.org Cc: Borislav Petkov References: <1507573730-8083-1-git-send-email-mark.rutland@arm.com> <1507573730-8083-3-git-send-email-mark.rutland@arm.com> From: Thor Thayer Message-ID: <0b61c449-4aa9-095d-fd83-b177670f3fbb@linux.intel.com> Date: Mon, 9 Oct 2017 18:12:10 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <1507573730-8083-3-git-send-email-mark.rutland@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/09/2017 01:28 PM, Mark Rutland wrote: > For several reasons, it is desirable to use {READ,WRITE}_ONCE() in > preference to ACCESS_ONCE(), and new code is expected to use one of the > former. So far, there's been no reason to change most existing uses of > ACCESS_ONCE(), as these aren't currently harmful. > > However, for some features it is necessary to instrument reads and > writes separately, which is not possible with ACCESS_ONCE(). This > distinction is critical to correct operation. > > It's possible to transform the bulk of kernel code using the Coccinelle > script below. However, this doesn't handle comments, leaving references > to ACCESS_ONCE() instances which have been removed. As a preparatory > step, this patch converts the Altera EDAC code and comments to use > {READ,WRITE}_ONCE() consistently. > > ---- > virtual patch > > @ depends on patch @ > expression E1, E2; > @@ > > - ACCESS_ONCE(E1) = E2 > + WRITE_ONCE(E1, E2) > > @ depends on patch @ > expression E; > @@ > > - ACCESS_ONCE(E) > + READ_ONCE(E) > ---- > > Signed-off-by: Mark Rutland > Cc: Borislav Petkov > Cc: Thor Thayer > --- > drivers/edac/altera_edac.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/edac/altera_edac.c b/drivers/edac/altera_edac.c > index 346c498..11d6419 100644 > --- a/drivers/edac/altera_edac.c > +++ b/drivers/edac/altera_edac.c > @@ -175,11 +175,11 @@ static ssize_t altr_sdr_mc_err_inject_write(struct file *file, > /* > * To trigger the error, we need to read the data back > * (the data was written with errors above). > - * The ACCESS_ONCE macros and printk are used to prevent the > + * The READ_ONCE macros and printk are used to prevent the > * the compiler optimizing these reads out. > */ > - reg = ACCESS_ONCE(ptemp[0]); > - read_reg = ACCESS_ONCE(ptemp[1]); > + reg = READ_ONCE(ptemp[0]); > + read_reg = READ_ONCE(ptemp[1]); > /* Force Read */ > rmb(); > > @@ -618,7 +618,7 @@ static ssize_t altr_edac_device_trig(struct file *file, > for (i = 0; i < (priv->trig_alloc_sz / sizeof(*ptemp)); i++) { > /* Read data so we're in the correct state */ > rmb(); > - if (ACCESS_ONCE(ptemp[i])) > + if (READ_ONCE(ptemp[i])) > result = -1; > /* Toggle Error bit (it is latched), leave ECC enabled */ > writel(error_mask, (drvdata->base + priv->set_err_ofst)); > @@ -635,7 +635,7 @@ static ssize_t altr_edac_device_trig(struct file *file, > > /* Read out written data. ECC error caused here */ > for (i = 0; i < ALTR_TRIGGER_READ_WRD_CNT; i++) > - if (ACCESS_ONCE(ptemp[i]) != i) > + if (READ_ONCE(ptemp[i]) != i) > edac_printk(KERN_ERR, EDAC_DEVICE, > "Read doesn't match written data\n"); > > Tested on Cyclone5 and Arria10. Thanks! Acked-by: Thor Thayer