From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752285AbbCZRXL (ORCPT ); Thu, 26 Mar 2015 13:23:11 -0400 Received: from e06smtp16.uk.ibm.com ([195.75.94.112]:48049 "EHLO e06smtp16.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752144AbbCZRXI (ORCPT ); Thu, 26 Mar 2015 13:23:08 -0400 Message-ID: <55144077.3010907@de.ibm.com> Date: Thu, 26 Mar 2015 18:23:03 +0100 From: Christian Borntraeger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Peter Zijlstra , Linus Torvalds CC: Thomas Gleixner , "linux-next@vger.kernel.org" , Stephen Rothwell , Ingo Molnar , Davidlohr Bueso , Paul McKenney , "linux-kernel@vger.kernel.org" , "H. Peter Anvin" , Will Deacon Subject: Re: linux-next: build warnings after merge of the access_once tree References: <20150326193112.2c87eb39@canb.auug.org.au> <20150326103442.GV21418@twins.programming.kicks-ass.net> <20150326132750.GA2805@arm.com> <20150326142220.GY21418@twins.programming.kicks-ass.net> <20150326163647.GC21418@twins.programming.kicks-ass.net> <20150326170748.GD21418@twins.programming.kicks-ass.net> In-Reply-To: <20150326170748.GD21418@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15032617-0025-0000-0000-0000047A1F42 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 26.03.2015 um 18:07 schrieb Peter Zijlstra: > On Thu, Mar 26, 2015 at 09:45:07AM -0700, Linus Torvalds wrote: > >> Stop this idiocy. > > Yeah, clearly I can type faster than I can think straight :/ > > > In any case, I've the below patch; do you want to take it now or do you > want me to route it through tip/locking/urgent or something like that? Its not urgent. Current upstream has a broken check (gcc will not emit the warning if the function is static). I just fixed the check in my next tree but I can certainly drop that tree. > > --- > Subject: kernel: Remove atomicy checks from {READ,WRITE}_ONCE > From: Peter Zijlstra > Date: Thu, 26 Mar 2015 17:45:37 +0100 > > The fact that volatile allows for atomic load/stores is a special case > not a requirement for {READ,WRITE}_ONCE(). Their primary purpose is to > force the compiler to emit load/stores _once_. > > So remove the warning as it is correct behaviour. This also implies that > the u64 case is not 64bit only, so remove the #ifdef so we can generate > better code in that case. > > Cc: Stephen Rothwell > Cc: Christian Borntraeger > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: "H. Peter Anvin" > Cc: Davidlohr Bueso > Cc: Paul McKenney > Cc: Will Deacon > Acked-by: Linus Torvalds > Signed-off-by: Peter Zijlstra (Intel) Acked-by: Christian Borntraeger > --- > include/linux/compiler.h | 16 ---------------- > 1 file changed, 16 deletions(-) > > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 1b45e4a0519b..0e41ca0e5927 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -192,29 +192,16 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect); > > #include > > -static __always_inline void data_access_exceeds_word_size(void) > -#ifdef __compiletime_warning > -__compiletime_warning("data access exceeds word size and won't be atomic") > -#endif > -; > - > -static __always_inline void data_access_exceeds_word_size(void) > -{ > -} > - > static __always_inline void __read_once_size(const volatile void *p, void *res, int size) > { > switch (size) { > case 1: *(__u8 *)res = *(volatile __u8 *)p; break; > case 2: *(__u16 *)res = *(volatile __u16 *)p; break; > case 4: *(__u32 *)res = *(volatile __u32 *)p; break; > -#ifdef CONFIG_64BIT > case 8: *(__u64 *)res = *(volatile __u64 *)p; break; > -#endif > default: > barrier(); > __builtin_memcpy((void *)res, (const void *)p, size); > - data_access_exceeds_word_size(); > barrier(); > } > } > @@ -225,13 +212,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s > case 1: *(volatile __u8 *)p = *(__u8 *)res; break; > case 2: *(volatile __u16 *)p = *(__u16 *)res; break; > case 4: *(volatile __u32 *)p = *(__u32 *)res; break; > -#ifdef CONFIG_64BIT > case 8: *(volatile __u64 *)p = *(__u64 *)res; break; > -#endif > default: > barrier(); > __builtin_memcpy((void *)p, (const void *)res, size); > - data_access_exceeds_word_size(); > barrier(); > } > } >