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 668A9C433EF for ; Tue, 22 Mar 2022 15:54:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236214AbiCVP4O (ORCPT ); Tue, 22 Mar 2022 11:56:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58514 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236030AbiCVP4N (ORCPT ); Tue, 22 Mar 2022 11:56:13 -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 890E639D for ; Tue, 22 Mar 2022 08:54:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1647964484; 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=bhnT3KW2N7nGUFmNkySnEopkUtzZ8brHDUQP8GeFjGo=; b=US2MxyWsyB3+4ufCqnt2P8fqB8gOLPFsfnexkcJ1mfI9c3exHdrqAAg1FhvDtfcB8KC13I o2nAmzyBVvgD0ImCd4koStkKFqxMkZ4MbWCX6CdV1Iaxs9zP1TnL2RPWZTTK5Y+X2OoB35 AF2fHf3XkqIl6jgJAXISJx9WEFLG3vY= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-428-j0LrWmyDNnym6QHTL5OVNg-1; Tue, 22 Mar 2022 11:54:39 -0400 X-MC-Unique: j0LrWmyDNnym6QHTL5OVNg-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0F6EE29ABA2E; Tue, 22 Mar 2022 15:54:38 +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 99C5A4229D0; Tue, 22 Mar 2022 15:54:37 +0000 (UTC) Message-ID: <54d6221d-0c4f-9329-042d-4f74c4ea288f@redhat.com> Date: Tue, 22 Mar 2022 11:54:37 -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 , guoren@kernel.org Cc: 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> From: Waiman Long In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org 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. Cheers, Longman