From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753070Ab2LKIKv (ORCPT ); Tue, 11 Dec 2012 03:10:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:24940 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751421Ab2LKIKu convert rfc822-to-8bit (ORCPT ); Tue, 11 Dec 2012 03:10:50 -0500 Date: Tue, 11 Dec 2012 10:10:24 +0200 From: Gleb Natapov To: Zhang Yanfei 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 Message-ID: <20121211081024.GC11016@redhat.com> References: <50C18168.305@cn.fujitsu.com> <20121210203014.GB2402@amt.cnet> <50C6E927.9040605@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: <50C6E927.9040605@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Gleb.