From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84029C433EF for ; Thu, 30 Sep 2021 13:22:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63DD261139 for ; Thu, 30 Sep 2021 13:22:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351167AbhI3NYG (ORCPT ); Thu, 30 Sep 2021 09:24:06 -0400 Received: from pegase2.c-s.fr ([93.17.235.10]:44729 "EHLO pegase2.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348651AbhI3NYF (ORCPT ); Thu, 30 Sep 2021 09:24:05 -0400 Received: from localhost (mailhub3.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4HKv6g3gh2z9sTd; Thu, 30 Sep 2021 15:22:19 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 5pJF2Y4Fg1sI; Thu, 30 Sep 2021 15:22:19 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4HKv6g2TRfz9sTF; Thu, 30 Sep 2021 15:22:19 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 33DE78B773; Thu, 30 Sep 2021 15:22:19 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 83kkFvX7Whf9; Thu, 30 Sep 2021 15:22:19 +0200 (CEST) Received: from PO20335.IDSI0.si.c-s.fr (unknown [192.168.203.149]) by messagerie.si.c-s.fr (Postfix) with ESMTP id F22568B763; Thu, 30 Sep 2021 15:22:17 +0200 (CEST) Subject: Re: [PATCH v2 5/7] sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y To: Ard Biesheuvel Cc: Linux Kernel Mailing List , Keith Packard , Russell King , Catalin Marinas , Will Deacon , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Paul Walmsley , Palmer Dabbelt , Albert Ou , Heiko Carstens , Mark Rutland References: <20210930125813.197418-1-ardb@kernel.org> <20210930125813.197418-6-ardb@kernel.org> <427566ca-80c0-56eb-880b-908bd4a71e9a@csgroup.eu> From: Christophe Leroy Message-ID: Date: Thu, 30 Sep 2021 15:22:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr-FR Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 30/09/2021 à 15:12, Ard Biesheuvel a écrit : > On Thu, 30 Sept 2021 at 15:09, Christophe Leroy > wrote: >> >> >> >> Le 30/09/2021 à 14:58, Ard Biesheuvel a écrit : >>> THREAD_INFO_IN_TASK moved the CPU field out of thread_info, but this >>> causes some issues on architectures that define raw_smp_processor_id() >>> in terms of this field, due to the fact that #include'ing linux/sched.h >>> to get at struct task_struct is problematic in terms of circular >>> dependencies. >>> >>> Given that thread_info and task_struct are the same data structure >>> anyway when THREAD_INFO_IN_TASK=y, let's move it back so that having >>> access to the type definition of struct thread_info is sufficient to >>> reference the CPU number of the current task. >>> >>> Note that this requires THREAD_INFO_IN_TASK's definition of the >>> task_thread_info() helper to be updated, as task_cpu() takes a >>> pointer-to-const, whereas task_thread_info() (which is used to generate >>> lvalues as well), needs a non-const pointer. So make it a macro instead. >>> >>> Signed-off-by: Ard Biesheuvel >>> Acked-by: Catalin Marinas >>> Acked-by: Mark Rutland >>> Acked-by: Michael Ellerman >>> --- >>> arch/arm64/kernel/asm-offsets.c | 1 - >>> arch/arm64/kernel/head.S | 2 +- >>> arch/powerpc/kernel/asm-offsets.c | 2 +- >>> arch/powerpc/kernel/smp.c | 2 +- >>> include/linux/sched.h | 13 +------------ >>> kernel/sched/sched.h | 4 ---- >>> 6 files changed, 4 insertions(+), 20 deletions(-) >>> >>> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c >>> index cee9f3e9f906..0bfc048221af 100644 >>> --- a/arch/arm64/kernel/asm-offsets.c >>> +++ b/arch/arm64/kernel/asm-offsets.c >>> @@ -27,7 +27,6 @@ >>> int main(void) >>> { >>> DEFINE(TSK_ACTIVE_MM, offsetof(struct task_struct, active_mm)); >>> - DEFINE(TSK_CPU, offsetof(struct task_struct, cpu)); >>> BLANK(); >>> DEFINE(TSK_TI_CPU, offsetof(struct task_struct, thread_info.cpu)); >>> DEFINE(TSK_TI_FLAGS, offsetof(struct task_struct, thread_info.flags)); >>> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S >>> index 17962452e31d..6a98f1a38c29 100644 >>> --- a/arch/arm64/kernel/head.S >>> +++ b/arch/arm64/kernel/head.S >>> @@ -412,7 +412,7 @@ SYM_FUNC_END(__create_page_tables) >>> scs_load \tsk >>> >>> adr_l \tmp1, __per_cpu_offset >>> - ldr w\tmp2, [\tsk, #TSK_CPU] >>> + ldr w\tmp2, [\tsk, #TSK_TI_CPU] >> >> Why do you need to change the name ? >> >> For powerpc64, you leave TASK_CPU. >> > > Because arm64 has a clear idiom here, where TSK_TI_ is used for > thread_info fields accessed via a task_struct pointer. Also, it only > occurs once in the code. > > Power does not seem to have this idiom, and TASK_CPU is used in many > more places, so I don't think it makes sense to change its name. In the old days it was called TI_CPU, was changed by commit f7354ccac844 ("powerpc/32: Remove CURRENT_THREAD_INFO and rename TI_CPU") after commit ed1cd6deb013 ("powerpc: Activate CONFIG_THREAD_INFO_IN_TASK") I don't have a strong opinion about it but we have: $ git grep thread_info arch/powerpc/kernel/asm-offsets.c arch/powerpc/kernel/asm-offsets.c:#include arch/powerpc/kernel/asm-offsets.c: OFFSET(TI_livepatch_sp, thread_info, livepatch_sp); arch/powerpc/kernel/asm-offsets.c: OFFSET(TI_LOCAL_FLAGS, thread_info, local_flags); arch/powerpc/kernel/asm-offsets.c: offsetof(struct task_struct, thread_info)); > > >>> ldr \tmp1, [\tmp1, \tmp2, lsl #3] >>> set_this_cpu_offset \tmp1 >>> .endm >>> diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c >>> index e563d3222d69..e37e4546034e 100644 >>> --- a/arch/powerpc/kernel/asm-offsets.c >>> +++ b/arch/powerpc/kernel/asm-offsets.c >>> @@ -93,7 +93,7 @@ int main(void) >>> #endif /* CONFIG_PPC64 */ >>> OFFSET(TASK_STACK, task_struct, stack); >>> #ifdef CONFIG_SMP >>> - OFFSET(TASK_CPU, task_struct, cpu); >>> + OFFSET(TASK_CPU, task_struct, thread_info.cpu); >>> #endif >>> >>> #ifdef CONFIG_LIVEPATCH >> >> ...