From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753018AbbHZE2y (ORCPT ); Wed, 26 Aug 2015 00:28:54 -0400 Received: from mail-pa0-f53.google.com ([209.85.220.53]:32805 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750979AbbHZE2u (ORCPT ); Wed, 26 Aug 2015 00:28:50 -0400 Date: Wed, 26 Aug 2015 12:28:34 +0800 From: Boqun Feng To: Will Deacon Cc: linux-arch@vger.kernel.org, Waiman.Long@hp.com, peterz@infradead.org, linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, mingo@kernel.org Subject: Re: [PATCH v5 0/8] Add generic support for relaxed atomics Message-ID: <20150826042834.GA10432@fixme-laptop.cn.ibm.com> References: <1438880084-18856-1-git-send-email-will.deacon@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1438880084-18856-1-git-send-email-will.deacon@arm.com> User-Agent: Mutt/1.5.23+102 (2ca89bed6448) (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Will, On Thu, Aug 06, 2015 at 05:54:36PM +0100, Will Deacon wrote: > > Will Deacon (8): > atomics: add acquire/release/relaxed variants of some atomic > operations > asm-generic: rework atomic-long.h to avoid bulk code duplication > asm-generic: add relaxed/acquire/release variants for atomic_long_t > lockref: remove homebrew cmpxchg64_relaxed macro definition > locking/qrwlock: implement queue_write_unlock using smp_store_release > locking/qrwlock: make use of acquire/release/relaxed atomics > include/llist: use linux/atomic.h instead of asm/cmpxchg.h Should we step further to privatize asm/cmpxchg.h entirely? Keep it only included in arch/*? Because after your next patch, in some configurations, asm/cmpxchg.h of ARM only provides the definition of {cmpxchg,xchg}_relaxed, others are built in linux/atomic.h. Further more, other architecture may implement asm/cmpxchg.h similarly in the future. So, IIUC, we actually don't guarantee all cmpxchg(), xchg() and their variants are defined in asm/cmpxchg.h. Though current users of asm/cmpxchg.h outside arch/* are fine, because they all happen to have got linux/atomic.h included. But we'd better change the current users and call out that asm/cmpxchg.h is privatized in the document. > ARM: atomics: define our SMP atomics in terms of _relaxed operations Consider this patch maybe? I did a simple build test on X86. Regards, Boqun ----------------------------------------------------------------------- Subject: [PATCH] atomics,cmpxchg: Privatize the inclusion of asm/cmpxchg.h After commit: atomics: add acquire/release/relaxed variants of some atomic operations Architectures may only provide {cmp,}xchg_relaxed definitions in asm/cmpxchg.h. Other variants, such as {cmp,}xchg, may be built in linux/atomic.h, which means simply including asm/cmpxchg.h may not get the definitions of all the{cmp,}xchg variants. Therefore, we should privatize the inclusions of asm/cmpxchg.h to keep it only included in arch/* and replace the inclusions outside with linux/atomic.h Signed-off-by: Boqun Feng --- Documentation/atomic_ops.txt | 4 ++++ drivers/net/ethernet/sfc/mcdi.c | 2 +- drivers/phy/phy-rcar-gen2.c | 3 +-- drivers/staging/speakup/selection.c | 2 +- 4 files changed, 7 insertions(+), 4 deletions(-) diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt index b19fc34..c9d1cac 100644 --- a/Documentation/atomic_ops.txt +++ b/Documentation/atomic_ops.txt @@ -542,6 +542,10 @@ The routines xchg() and cmpxchg() must provide the same exact memory-barrier semantics as the atomic and bit operations returning values. +Note: If someone wants to use xchg(), cmpxchg() and their variants, +linux/atomic.h should be included rather than asm/cmpxchg.h, unless +the code is in arch/* and can take care of itself. + Spinlocks and rwlocks have memory barrier expectations as well. The rule to follow is simple: diff --git a/drivers/net/ethernet/sfc/mcdi.c b/drivers/net/ethernet/sfc/mcdi.c index 81640f8..968383e 100644 --- a/drivers/net/ethernet/sfc/mcdi.c +++ b/drivers/net/ethernet/sfc/mcdi.c @@ -9,7 +9,7 @@ #include #include -#include +#include #include "net_driver.h" #include "nic.h" #include "io.h" diff --git a/drivers/phy/phy-rcar-gen2.c b/drivers/phy/phy-rcar-gen2.c index 39d9b29..117b495 100644 --- a/drivers/phy/phy-rcar-gen2.c +++ b/drivers/phy/phy-rcar-gen2.c @@ -17,8 +17,7 @@ #include #include #include - -#include +#include #define USBHS_LPSTS 0x02 #define USBHS_UGCTRL 0x80 diff --git a/drivers/staging/speakup/selection.c b/drivers/staging/speakup/selection.c index a031570..81c0888 100644 --- a/drivers/staging/speakup/selection.c +++ b/drivers/staging/speakup/selection.c @@ -7,7 +7,7 @@ #include #include #include -#include +#include #include "speakup.h"