From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753078Ab2LKIHE (ORCPT ); Tue, 11 Dec 2012 03:07:04 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:24620 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752934Ab2LKIHC convert rfc822-to-8bit (ORCPT ); Tue, 11 Dec 2012 03:07:02 -0500 X-IronPort-AV: E=Sophos;i="4.84,258,1355068800"; d="scan'208";a="6374362" Message-ID: <50C6E927.9040605@cn.fujitsu.com> Date: Tue, 11 Dec 2012 16:04:55 +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: Marcelo Tosatti CC: "Eric W. Biederman" , Gleb Natapov , "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> In-Reply-To: <20121210203014.GB2402@amt.cnet> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/12/11 16:06:12, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2012/12/11 16:06:13 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 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. Thanks Zhang Yanfei