From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752661Ab2G0J23 (ORCPT ); Fri, 27 Jul 2012 05:28:29 -0400 Received: from smtp.eu.citrix.com ([62.200.22.115]:21089 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752382Ab2G0J22 (ORCPT ); Fri, 27 Jul 2012 05:28:28 -0400 X-IronPort-AV: E=Sophos;i="4.77,666,1336348800"; d="scan'208";a="13730505" Message-ID: <1343381305.6812.116.camel@zakaz.uk.xensource.com> Subject: Re: [Xen-devel] [PATCH 04/24] xen/arm: sync_bitops From: Ian Campbell To: Konrad Rzeszutek Wilk CC: Stefano Stabellini , "linux-kernel@vger.kernel.org" , "xen-devel@lists.xensource.com" , "linaro-dev@lists.linaro.org" , "arnd@arndb.de" , "catalin.marinas@arm.com" , "Tim (Xen.org)" , "linux-arm-kernel@lists.infradead.org" Date: Fri, 27 Jul 2012 10:28:25 +0100 In-Reply-To: <20120726163759.GE9222@phenom.dumpdata.com> References: <1343316846-25860-4-git-send-email-stefano.stabellini@eu.citrix.com> <20120726163759.GE9222@phenom.dumpdata.com> Organization: Citrix Systems, Inc. Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.3-1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2012-07-26 at 17:37 +0100, Konrad Rzeszutek Wilk wrote: > On Thu, Jul 26, 2012 at 04:33:46PM +0100, Stefano Stabellini wrote: > > sync_bitops functions are equivalent to the SMP implementation of the > > original functions, independently from CONFIG_SMP being defined. > > So why can't the code be changed to use that? Is it that > the _set_bit, _clear_bit, etc are not available with !CONFIG_SMP? _set_bit etc are not SMP safe if !CONFIG_SMP. But under Xen you might be communicating with a completely external entity who might be on another CPU (e.g. two uniprocessor guests communicating via event channels and grant tables). So we need a variant of the bit ops which are SMP safe even on a UP kernel. The users are common code and the sync_foo vs foo distinction matters on some platforms (e.g. x86 where a UP kernel would omit the LOCK prefix for the normal ones). > > > > > Signed-off-by: Stefano Stabellini > > --- > > arch/arm/include/asm/sync_bitops.h | 17 +++++++++++++++++ > > 1 files changed, 17 insertions(+), 0 deletions(-) > > create mode 100644 arch/arm/include/asm/sync_bitops.h > > > > diff --git a/arch/arm/include/asm/sync_bitops.h b/arch/arm/include/asm/sync_bitops.h > > new file mode 100644 > > index 0000000..d975092903 > > --- /dev/null > > +++ b/arch/arm/include/asm/sync_bitops.h > > @@ -0,0 +1,17 @@ > > +#ifndef __ASM_SYNC_BITOPS_H__ > > +#define __ASM_SYNC_BITOPS_H__ > > + > > +#include > > +#include > > + > > +#define sync_set_bit(nr, p) _set_bit(nr, p) > > +#define sync_clear_bit(nr, p) _clear_bit(nr, p) > > +#define sync_change_bit(nr, p) _change_bit(nr, p) > > +#define sync_test_and_set_bit(nr, p) _test_and_set_bit(nr, p) > > +#define sync_test_and_clear_bit(nr, p) _test_and_clear_bit(nr, p) > > +#define sync_test_and_change_bit(nr, p) _test_and_change_bit(nr, p) > > +#define sync_test_bit(nr, addr) test_bit(nr, addr) > > +#define sync_cmpxchg cmpxchg > > + > > + > > +#endif > > -- > > 1.7.2.5 > > > > > > _______________________________________________ > > Xen-devel mailing list > > Xen-devel@lists.xen.org > > http://lists.xen.org/xen-devel