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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F2455C433F5 for ; Tue, 22 Mar 2022 21:14:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235261AbiCVVPl (ORCPT ); Tue, 22 Mar 2022 17:15:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235260AbiCVVPl (ORCPT ); Tue, 22 Mar 2022 17:15:41 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B7814192 for ; Tue, 22 Mar 2022 14:14:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1647983651; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SIVLkwlhPM3w906YxQwZL+nXYzlTqcHmn11/FV0IJ2I=; b=Vo0jLs4Et8LNC/vvncdtyRc9LmfTrqI+CxTG+Foa9/PZbx991eKw62bvfd27KlZvpC2LQp 8fDY2pO1fTQ6sWb7+OBteX+IdvbRleJUeiFYu2hWynWImOZVgFwVIqOblrPByU3xo8doke IjxuBxtsEmkxIIUQOaaHu29zJlIS9lM= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-444-gAQqERV8OKCorngkS2_1Ew-1; Tue, 22 Mar 2022 17:14:06 -0400 X-MC-Unique: gAQqERV8OKCorngkS2_1Ew-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D5727803B22; Tue, 22 Mar 2022 21:14:05 +0000 (UTC) Received: from [10.18.17.215] (dhcp-17-215.bos.redhat.com [10.18.17.215]) by smtp.corp.redhat.com (Postfix) with ESMTP id 793A440D0166; Tue, 22 Mar 2022 21:14:05 +0000 (UTC) Message-ID: Date: Tue, 22 Mar 2022 17:14:05 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [OpenRISC] [PATCH V2 1/5] asm-generic: ticket-lock: New generic ticket-based spinlock Content-Language: en-US To: Stafford Horne Cc: guoren@kernel.org, palmer@dabbelt.com, arnd@arndb.de, boqun.feng@gmail.com, peterz@infradead.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-csky@vger.kernel.org, openrisc@lists.librecores.org, Palmer Dabbelt , linux-riscv@lists.infradead.org References: <20220319035457.2214979-1-guoren@kernel.org> <20220319035457.2214979-2-guoren@kernel.org> <54d6221d-0c4f-9329-042d-4f74c4ea288f@redhat.com> From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On 3/22/22 17:06, Stafford Horne wrote: > On Tue, Mar 22, 2022 at 11:54:37AM -0400, Waiman Long wrote: >> On 3/21/22 23:10, Stafford Horne wrote: >>> Hello, >>> >>> There is a problem with this patch on Big Endian machines, see below. >>> >>> On Sat, Mar 19, 2022 at 11:54:53AM +0800, guoren@kernel.org wrote: >>>> From: Peter Zijlstra >>>> >>>> This is a simple, fair spinlock. Specifically it doesn't have all the >>>> subtle memory model dependencies that qspinlock has, which makes it more >>>> suitable for simple systems as it is more likely to be correct. >>>> >>>> [Palmer: commit text] >>>> Signed-off-by: Palmer Dabbelt >>>> >>>> -- >>>> >>>> I have specifically not included Peter's SOB on this, as he sent his >>>> original patch >>>> >>>> without one. >>>> --- >>>> include/asm-generic/spinlock.h | 11 +++- >>>> include/asm-generic/spinlock_types.h | 15 +++++ >>>> include/asm-generic/ticket-lock-types.h | 11 ++++ >>>> include/asm-generic/ticket-lock.h | 86 +++++++++++++++++++++++++ >>>> 4 files changed, 120 insertions(+), 3 deletions(-) >>>> create mode 100644 include/asm-generic/spinlock_types.h >>>> create mode 100644 include/asm-generic/ticket-lock-types.h >>>> create mode 100644 include/asm-generic/ticket-lock.h >>>> >>>> diff --git a/include/asm-generic/ticket-lock.h b/include/asm-generic/ticket-lock.h >>>> new file mode 100644 >>>> index 000000000000..59373de3e32a >>>> --- /dev/null >>>> +++ b/include/asm-generic/ticket-lock.h >>> ... >>> >>>> +static __always_inline void ticket_unlock(arch_spinlock_t *lock) >>>> +{ >>>> + u16 *ptr = (u16 *)lock + __is_defined(__BIG_ENDIAN); >>> As mentioned, this patch series breaks SMP on OpenRISC. I traced it to this >>> line. The above `__is_defined(__BIG_ENDIAN)` does not return 1 as expected >>> even on BIG_ENDIAN machines. This works: >>> >>> >>> diff --git a/include/asm-generic/ticket-lock.h b/include/asm-generic/ticket-lock.h >>> index 59373de3e32a..52b5dc9ffdba 100644 >>> --- a/include/asm-generic/ticket-lock.h >>> +++ b/include/asm-generic/ticket-lock.h >>> @@ -26,6 +26,7 @@ >>> #define __ASM_GENERIC_TICKET_LOCK_H >>> #include >>> +#include >>> #include >>> static __always_inline void ticket_lock(arch_spinlock_t *lock) >>> @@ -51,7 +52,7 @@ static __always_inline bool ticket_trylock(arch_spinlock_t *lock) >>> static __always_inline void ticket_unlock(arch_spinlock_t *lock) >>> { >>> - u16 *ptr = (u16 *)lock + __is_defined(__BIG_ENDIAN); >>> + u16 *ptr = (u16 *)lock + IS_ENABLED(CONFIG_CPU_BIG_ENDIAN); >>> u32 val = atomic_read(lock); >>> smp_store_release(ptr, (u16)val + 1); >>> >>> >>>> + u32 val = atomic_read(lock); >>>> + >>>> + smp_store_release(ptr, (u16)val + 1); >>>> +} >>>> + >> __BIG_ENDIAN is defined in . I believe that if you include >> , the second hunk is not really needed and vice versa. > I thought so too, but it doesn't seem to work. I think __is_defined is not > doing what we think in this context. It looks like __is_defined works when a > macro is defined as 1, in this case we have __BIG_ENDIAN 4321. You are right. __is_defined() only for 1 or not 1. So it can't be used for __BIG_ENDIAN. I was not aware of that. Anyway, the include is not really needed then. Cheers, Longman