Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964953AbbLVVOz (ORCPT ); Tue, 22 Dec 2015 16:14:55 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:53035 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964916AbbLVVOY (ORCPT ); Tue, 22 Dec 2015 16:14:24 -0500 Date: Tue, 22 Dec 2015 13:14:23 -0800 From: Andrew Morton To: Xunlei Pang Cc: Minfei Huang , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, dyoung@redhat.com, ebiederm@xmission.com Subject: Re: [PATCH] kexec: Move some memembers and definitions within the scope of CONFIG_KEXEC_FILE Message-Id: <20151222131423.e173a94907f8caf5b70eccae@linux-foundation.org> In-Reply-To: <567936B7.5020702@redhat.com> References: <1450678154-12581-1-git-send-email-xlpang@redhat.com> <20151222104704.GA28313@dhcp-128-25.nay.redhat.com> <567936B7.5020702@redhat.com> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1836 Lines: 42 On Tue, 22 Dec 2015 19:40:39 +0800 Xunlei Pang wrote: > > Following functions will be used only in kexec_file. Please wrap them in > > CONFIG_KEXEC_FILE. > > > > int __weak arch_kexec_kernel_image_probe(struct kimage *image, void *buf, > > unsigned long buf_len); > > void * __weak arch_kexec_kernel_image_load(struct kimage *image); > > int __weak arch_kimage_file_post_load_cleanup(struct kimage *image); > > int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf, > > unsigned long buf_len); > > int __weak arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr, > > Elf_Shdr *sechdrs, unsigned int relsec); > > int __weak arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, > > unsigned int relsec); > > Thanks for the comment. > > I noticed this as well, but seems for the function declarations we don't need do this, > since they don't consume the actual space. > > For example, in the include/linux/timekeeping.h > /* > * RTC specific > */ > extern bool timekeeping_rtc_skipsuspend(void); > extern bool timekeeping_rtc_skipresume(void); > > extern void timekeeping_inject_sleeptime64(struct timespec64 *delta); > > also not embraced by the corresponding macros. Yes. If we add the ifdefs then a programming error will be detected at compile time. If we don't add the ifdefs then that error will be detected at link time. So the ifdefs provide a quite small advantage, while making the code harder to read and harder to maintain. I believe that "no ifdefs" is the better side of this tradeoff. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/