Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751500AbdF0AL7 (ORCPT ); Mon, 26 Jun 2017 20:11:59 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:51492 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751440AbdF0ALx (ORCPT ); Mon, 26 Jun 2017 20:11:53 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 26 Jun 2017 17:11:51 -0700 From: Sodagudi Prasad To: David Rientjes Cc: Andrew Morton , Mark Rutland , will.deacon@arm.com, catalin.marinas@arm.com, mingo@kernel.org, peterz@infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Matthias Kaehlcke Subject: Re: [patch resend 4.12] compiler, clang: always inline when CONFIG_OPTIMIZE_INLINING is disabled In-Reply-To: References: Message-ID: User-Agent: Roundcube Webmail/1.2.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4012 Lines: 109 On 2017-06-26 16:03, David Rientjes wrote: > The motivation of commit abb2ea7dfd82 ("compiler, clang: suppress > warning > for unused static inline functions") is to suppress clang's warnings > about > unused static inline functions. > > For configs without CONFIG_OPTIMIZE_INLINING enabled, such as any > non-x86 > architecture, `inline' in the kernel implies that > __attribute__((always_inline)) is used. > > Some code depends on that behavior, see > https://lkml.org/lkml/2017/6/13/918: > > net/built-in.o: In function `__xchg_mb': > arch/arm64/include/asm/cmpxchg.h:99: undefined reference to > `__compiletime_assert_99' > arch/arm64/include/asm/cmpxchg.h:99: undefined reference to > `__compiletime_assert_99 > > The full fix would be to identify these breakages and annotate the > functions with __always_inline instead of `inline'. But since we are > late > in the 4.12-rc cycle, simply carry forward the forced inlining behavior > and work toward moving arm64, and other architectures, toward > CONFIG_OPTIMIZE_INLINING behavior. > > Reported-by: Sodagudi Prasad > Tested-by: Matthias Kaehlcke > Signed-off-by: David Rientjes > --- > Resend of http://marc.info/?l=linux-kernel&m=149681501816319 for 4.12 > inclusion. > > Prasad, please add your Tested-by. > I have compile tested this change with clang, please add - Tested-by: Sodagudi Prasad -Thanks, Prasad > include/linux/compiler-clang.h | 8 -------- > include/linux/compiler-gcc.h | 18 +++++++++++------- > 2 files changed, 11 insertions(+), 15 deletions(-) > > diff --git a/include/linux/compiler-clang.h > b/include/linux/compiler-clang.h > --- a/include/linux/compiler-clang.h > +++ b/include/linux/compiler-clang.h > @@ -15,11 +15,3 @@ > * with any version that can compile the kernel > */ > #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), > __COUNTER__) > - > -/* > - * GCC does not warn about unused static inline functions for > - * -Wunused-function. This turns out to avoid the need for complex > #ifdef > - * directives. Suppress the warning in clang as well. > - */ > -#undef inline > -#define inline inline __attribute__((unused)) notrace > diff --git a/include/linux/compiler-gcc.h > b/include/linux/compiler-gcc.h > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -66,18 +66,22 @@ > > /* > * Force always-inline if the user requests it so via the .config, > - * or if gcc is too old: > + * or if gcc is too old. > + * GCC does not warn about unused static inline functions for > + * -Wunused-function. This turns out to avoid the need for complex > #ifdef > + * directives. Suppress the warning in clang as well by using > "unused" > + * function attribute, which is redundant but not harmful for gcc. > */ > #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ > !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4) > -#define inline inline __attribute__((always_inline)) notrace > -#define __inline__ __inline__ __attribute__((always_inline)) notrace > -#define __inline __inline __attribute__((always_inline)) notrace > +#define inline inline __attribute__((always_inline,unused)) notrace > +#define __inline__ __inline__ __attribute__((always_inline,unused)) > notrace > +#define __inline __inline __attribute__((always_inline,unused)) > notrace > #else > /* A lot of inline functions can cause havoc with function tracing */ > -#define inline inline notrace > -#define __inline__ __inline__ notrace > -#define __inline __inline notrace > +#define inline inline __attribute__((unused)) notrace > +#define __inline__ __inline__ __attribute__((unused)) notrace > +#define __inline __inline __attribute__((unused)) notrace > #endif > > #define __always_inline inline __attribute__((always_inline)) -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, Linux Foundation Collaborative Project