From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Berg Subject: Re: [PATCH 09/19] net: average: Kill off ACCESS_ONCE() Date: Tue, 24 Oct 2017 07:58:11 +0200 Message-ID: <1508824691.2639.26.camel@sipsolutions.net> References: <20171023210408.GA2930@linux.vnet.ibm.com> <1508792849-3115-9-git-send-email-paulmck@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1508792849-3115-9-git-send-email-paulmck@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: "Paul E. McKenney" , "mingo@kernel.org" Cc: "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "will.deacon@arm.com" , "mark.rutland@arm.com" , "snitzer@redhat.com" , "thor.thayer@linux.intel.com" , "viro@zeniv.linux.org.uk" , "davem@davemloft.net" , "shuah@kernel.org" , "mpe@ellerman.id.au" , "tj@kernel.org" , "torvalds@linux-foundation.org" List-Id: linux-arch.vger.kernel.org On Mon, 2017-10-23 at 21:07 +0000, Paul E. McKenney wrote: > From: Mark Rutland > > 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 pick up some uses, including those > in . As a preparatory step, this patch converts the > file to use {READ,WRITE}_ONCE() consistently. > > At the same time, this patch addds missing includes necessary for > {READ,WRITE}_ONCE(), *BUG_ON*(), and ilog2(). > > ---- > 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: Johannes Berg Reviewed-by: Johannes Berg Let me know if you want me to apply this, since I seem to be the average.h maintainer :-) johannes From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from s3.sipsolutions.net ([144.76.63.242]:58184 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751432AbdJXG3F (ORCPT ); Tue, 24 Oct 2017 02:29:05 -0400 Message-ID: <1508824691.2639.26.camel@sipsolutions.net> Subject: Re: [PATCH 09/19] net: average: Kill off ACCESS_ONCE() From: Johannes Berg Date: Tue, 24 Oct 2017 07:58:11 +0200 In-Reply-To: <1508792849-3115-9-git-send-email-paulmck@linux.vnet.ibm.com> References: <20171023210408.GA2930@linux.vnet.ibm.com> <1508792849-3115-9-git-send-email-paulmck@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: "Paul E. McKenney" , "mingo@kernel.org" Cc: "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , "will.deacon@arm.com" , "mark.rutland@arm.com" , "snitzer@redhat.com" , "thor.thayer@linux.intel.com" , "viro@zeniv.linux.org.uk" , "davem@davemloft.net" , "shuah@kernel.org" , "mpe@ellerman.id.au" , "tj@kernel.org" , "torvalds@linux-foundation.org" Message-ID: <20171024055811.jsLZZK_i3we_4dbZWX3yW1L1iPy4IqFembIhtne20Kg@z> On Mon, 2017-10-23 at 21:07 +0000, Paul E. McKenney wrote: > From: Mark Rutland > > 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 pick up some uses, including those > in . As a preparatory step, this patch converts the > file to use {READ,WRITE}_ONCE() consistently. > > At the same time, this patch addds missing includes necessary for > {READ,WRITE}_ONCE(), *BUG_ON*(), and ilog2(). > > ---- > 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: Johannes Berg Reviewed-by: Johannes Berg Let me know if you want me to apply this, since I seem to be the average.h maintainer :-) johannes