From mboxrd@z Thu Jan 1 00:00:00 1970 From: konrad.wilk@oracle.com (Konrad Rzeszutek Wilk) Date: Wed, 1 Aug 2012 10:35:51 -0400 Subject: [Xen-devel] [PATCH 04/24] xen/arm: sync_bitops In-Reply-To: <1343381305.6812.116.camel@zakaz.uk.xensource.com> References: <1343316846-25860-4-git-send-email-stefano.stabellini@eu.citrix.com> <20120726163759.GE9222@phenom.dumpdata.com> <1343381305.6812.116.camel@zakaz.uk.xensource.com> Message-ID: <20120801143551.GI7227@phenom.dumpdata.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Jul 27, 2012 at 10:28:25AM +0100, Ian Campbell wrote: > 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). OK, that makes sense. Stefano can you include that comment in the git commit description and in the sync_bitops.h file please? > > > > > > > > > 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 at lists.xen.org > > > http://lists.xen.org/xen-devel > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755260Ab2HAOpO (ORCPT ); Wed, 1 Aug 2012 10:45:14 -0400 Received: from acsinet15.oracle.com ([141.146.126.227]:30256 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753970Ab2HAOpL (ORCPT ); Wed, 1 Aug 2012 10:45:11 -0400 Date: Wed, 1 Aug 2012 10:35:51 -0400 From: Konrad Rzeszutek Wilk To: Ian Campbell 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" Subject: Re: [Xen-devel] [PATCH 04/24] xen/arm: sync_bitops Message-ID: <20120801143551.GI7227@phenom.dumpdata.com> References: <1343316846-25860-4-git-send-email-stefano.stabellini@eu.citrix.com> <20120726163759.GE9222@phenom.dumpdata.com> <1343381305.6812.116.camel@zakaz.uk.xensource.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1343381305.6812.116.camel@zakaz.uk.xensource.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 27, 2012 at 10:28:25AM +0100, Ian Campbell wrote: > 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). OK, that makes sense. Stefano can you include that comment in the git commit description and in the sync_bitops.h file please? > > > > > > > > > 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 > From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [Xen-devel] [PATCH 04/24] xen/arm: sync_bitops Date: Wed, 1 Aug 2012 10:35:51 -0400 Message-ID: <20120801143551.GI7227@phenom.dumpdata.com> References: <1343316846-25860-4-git-send-email-stefano.stabellini@eu.citrix.com> <20120726163759.GE9222@phenom.dumpdata.com> <1343381305.6812.116.camel@zakaz.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1343381305.6812.116.camel-o4Be2W7LfRlXesXXhkcM7miJhflN2719@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linaro-dev-bounces-cunTk1MwBs8s++Sfvej+rw@public.gmane.org Errors-To: linaro-dev-bounces-cunTk1MwBs8s++Sfvej+rw@public.gmane.org To: Ian Campbell Cc: "xen-devel-GuqFBffKawuULHF6PoxzQEEOCMrvLtNR@public.gmane.org" , "linaro-dev-cunTk1MwBs8s++Sfvej+rw@public.gmane.org" , "arnd-r2nGTMty4D4@public.gmane.org" , "catalin.marinas-5wv7dgnIgG8@public.gmane.org" , "Tim (Xen.org)" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: xen-devel@lists.xenproject.org On Fri, Jul 27, 2012 at 10:28:25AM +0100, Ian Campbell wrote: > 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). OK, that makes sense. Stefano can you include that comment in the git commit description and in the sync_bitops.h file please? > > > > > > > > > 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-GuqFBffKawuEi8DpZVb4nw@public.gmane.org > > > http://lists.xen.org/xen-devel >