From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752653Ab2LKJLt (ORCPT ); Tue, 11 Dec 2012 04:11:49 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:48459 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751558Ab2LKJLq convert rfc822-to-8bit (ORCPT ); Tue, 11 Dec 2012 04:11:46 -0500 X-IronPort-AV: E=Sophos;i="4.84,258,1355068800"; d="scan'208";a="6374918" Message-ID: <50C6F84D.7010701@cn.fujitsu.com> Date: Tue, 11 Dec 2012 17:09:33 +0800 From: Zhang Yanfei User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.8) Gecko/20121012 Thunderbird/10.0.8 MIME-Version: 1.0 To: Gleb Natapov CC: Marcelo Tosatti , "Eric W. Biederman" , "kvm@vger.kernel.org" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , kbuild test robot Subject: Re: [PATCH] x86/kexec: crash_vmclear_local_vmcss needs __rcu References: <50C18168.305@cn.fujitsu.com> <20121210203014.GB2402@amt.cnet> <50C6E927.9040605@cn.fujitsu.com> <20121211081024.GC11016@redhat.com> In-Reply-To: <20121211081024.GC11016@redhat.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/12/11 17:10:50, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/12/11 17:10:51 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 于 2012年12月11日 16:10, Gleb Natapov 写道: > On Tue, Dec 11, 2012 at 04:04:55PM +0800, Zhang Yanfei wrote: >> 于 2012年12月11日 04:30, Marcelo Tosatti 写道: >>> On Fri, Dec 07, 2012 at 01:40:56PM +0800, Zhang Yanfei wrote: >>>> This removes the sparse warning: >>>> arch/x86/kernel/crash.c:49:32: sparse: incompatible types in comparison expression (different address spaces) >>>> >>>> Reported-by: kbuild test robot >>>> Signed-off-by: Zhang Yanfei >>>> --- >>>> arch/x86/include/asm/kexec.h | 4 +++- >>>> arch/x86/kernel/crash.c | 4 ++-- >>>> 2 files changed, 5 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h >>>> index 28feeba..16882cd 100644 >>>> --- a/arch/x86/include/asm/kexec.h >>>> +++ b/arch/x86/include/asm/kexec.h >>>> @@ -163,7 +163,9 @@ struct kimage_arch { >>>> }; >>>> #endif >>>> >>>> -extern void (*crash_vmclear_loaded_vmcss)(void); >>>> +extern void __rcu (*crash_vmclear_loaded_vmcss)(void); >>>> +#define vmclear_func_rcu(vmclear_func) \ >>>> + ((void (*)(void)) rcu_dereference(vmclear_func)) >>>> >>>> #endif /* __ASSEMBLY__ */ >>>> >>>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c >>>> index 2f6b8e8..50ce1d6 100644 >>>> --- a/arch/x86/kernel/crash.c >>>> +++ b/arch/x86/kernel/crash.c >>>> @@ -38,7 +38,7 @@ int in_crash_kexec; >>>> * >>>> * protected by rcu. >>>> */ >>>> -void (*crash_vmclear_loaded_vmcss)(void) = NULL; >>>> +void __rcu (*crash_vmclear_loaded_vmcss)(void) = NULL; >>> >>> Isnt this (__rcu AS tag) sufficient? After all, sparse is complaining >>> about namespaces. >>> >>> Creating a #define to cast seems excessive. >>> >>> >> >> I am not very familiar with the rcu. >> Adding __rcu tag could solve the problem. But it imported another warning >> when I try to assign rcu_dereference(crash_vmclear_loaded_vmcss) to >> do_vmclear_operation: >> >> arch/x86/kernel/crash.c:49:30: warning: incorrect type in assignment (different modifiers) >> arch/x86/kernel/crash.c:49:30: expected void ( *do_vmclear_operation )( ... ) >> arch/x86/kernel/crash.c:49:30: got void ( [noderef] * )( ... ) >> arch/x86/kernel/crash.c:49:30: warning: incorrect type in assignment (different modifiers) >> arch/x86/kernel/crash.c:49:30: expected void ( *do_vmclear_operation )( ... ) >> arch/x86/kernel/crash.c:49:30: got void ( [noderef] * )( ... ) >> >> So I made the #define to cast its type. >> >> If you have any suggestion, that'll be helpful. >> > Try to use typedef. > Thanks. typedef works.