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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DDC1EC3064D for ; Thu, 27 Jun 2024 13:59:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=N2wn7HfFqPOSXiYs/MGqbDqZ6ytmTbbwG4UsT7YcJHI=; b=3URIoyad0hyVBx 2hmdgNB/OQQlIZGBfbj6LdmC2O4sKH0PLYoVW2pXRTDJXceDoVPfzTmsac62JI/XVeip5vlM2IIaE Nv7qIaIIMhLX2NqBaAV022hCSTRg370bv9ldNN33370u+O/TeRmG66b9ikQ7T0xG4Vk9PiSMeo5re vHYEp0oBt/GqRV57lIlZDJwyJSO1dhzIYqDDmpnWBVNMSG6k6Y6QC/w2brRoMUkwpvj4zurZS2naU jSR8fLlunNpAl8l56h/DjncaPP2tBS4FfF1bdK+5uVfphaT6Tzds73kCHHlHjgxRB55cXka1nY0LO ie2ik782SibZn0cnyxtQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sMpeM-0000000AY7V-2zR8; Thu, 27 Jun 2024 13:58:58 +0000 Received: from mail-ed1-x533.google.com ([2a00:1450:4864:20::533]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sMpe6-0000000AY54-48WT for linux-riscv@lists.infradead.org; Thu, 27 Jun 2024 13:58:51 +0000 Received: by mail-ed1-x533.google.com with SMTP id 4fb4d7f45d1cf-57d07464aa9so1838180a12.2 for ; Thu, 27 Jun 2024 06:58:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1719496721; x=1720101521; darn=lists.infradead.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=Kq5kitpL+DNnXu/D9/hs8Bp0/3waJ/uTRKdNkzKgHOY=; b=VCHUq8ca2MvJY9ytN/rA/MUNHSgaYmYEWeV5ZpBonugyhYsfN5CMLTU8yhCfzXB+z/ 4wLFlrxQXXOHlPJ1J2k1G7v+6gyH6xVrrAn1yzNdcwa7e16DnTorcnkZIe7karaj5erJ 5kVhy+jHK3d9Jq+7UnUtX6bPqjI9in4D1vUC2EHQYSdcqgbtMJvhbHaGGvJmaybiSdvO vI+Aiyf5m2Z4VFVvZBCrKfDgquWKIHsZBuypIoQry+N9t1IRv5MuOK4nfZIP/dqsyifH TxXe6MLXWX/s7PPr0CI+3PvqE5FOitV2W/dpYCEUQUIuM4IB0RQy+nSQVOyJCevTygUB l16Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719496721; x=1720101521; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Kq5kitpL+DNnXu/D9/hs8Bp0/3waJ/uTRKdNkzKgHOY=; b=W1G0wJdtQOikCCQzkMf6OnQrEy7BuchblCtkfS770zcsfXeEGFi7FUYf+/ncteYA4P ajUtHi3IHCUqtqInkty2cCjZo1nvL6FE5mTMbPiE46w20qNNSqERYBZHh7EOnTgOj/cD D3Qz/ggbQ3kuq/sRnkQ5WPaW0pltPhXP8Nd+p746IA7h8sUXwx7kwDpI6ELHY5A3I1To z3LP/cfcG05i1/mvg5rd39n65fBjx7WQz0Z7sh1ver5fo51dkfmVWBaL+QGs8fr5Cnil YhBi7s0iSzrD38iIlPQcrVBPNi/qJ3TKabe8CAoZ18WQGkRpnHhi7fq3nJUZFTIMXPC+ lUjQ== X-Forwarded-Encrypted: i=1; AJvYcCVPzN6RyL6RbaKFfp3kqvjYsXke3INsKL2DGY3297e22kZVzeHXYDBohr+qazi1SENbPjvC9KHclOX7mkfZJmlTlE/caAVccLj5C90n7Cg6 X-Gm-Message-State: AOJu0YwebrjUA9FnAsYCNxSnWdcx2UIVxq9FRMokO5+VJPm3znEGOAdQ SsmXE5TveQBYjnPyotI+dczTRXVnP3dDNq/XtVfb/gCB/2CyoF7e X-Google-Smtp-Source: AGHT+IHvyluvD0SP5UIJpy0mzv9Rb/yj78D4vKm/kObn4l7XWRh5tCnb+ua1oj/MkdIB7mBGiA7dTQ== X-Received: by 2002:a17:906:48d0:b0:a69:13a2:4f6e with SMTP id a640c23a62f3a-a7245c70519mr687906566b.74.1719496720885; Thu, 27 Jun 2024 06:58:40 -0700 (PDT) Received: from andrea ([217.201.220.159]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a729d7c9628sm61491866b.202.2024.06.27.06.58.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Jun 2024 06:58:40 -0700 (PDT) Date: Thu, 27 Jun 2024 15:58:36 +0200 From: Andrea Parri To: Alexandre Ghiti Cc: Jonathan Corbet , Paul Walmsley , Palmer Dabbelt , Albert Ou , Nathan Chancellor , Peter Zijlstra , Ingo Molnar , Will Deacon , Waiman Long , Boqun Feng , Arnd Bergmann , Leonardo Bras , Guo Ren , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, Andrea Parri Subject: Re: [PATCH v2 07/10] riscv: Improve amoswap.X use in xchg() Message-ID: References: <20240626130347.520750-1-alexghiti@rivosinc.com> <20240626130347.520750-8-alexghiti@rivosinc.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240626130347.520750-8-alexghiti@rivosinc.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240627_065845_518655_FFE814CA X-CRM114-Status: GOOD ( 15.87 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Wed, Jun 26, 2024 at 03:03:44PM +0200, Alexandre Ghiti wrote: > xchg() uses amoswap.X instructions from Zabha but still uses > the LR/SC acquire/release semantics which require barriers. > > Let's improve that by using proper amoswap acquire/release semantics in > order to avoid any of those barriers. > > Suggested-by: Andrea Parri > Signed-off-by: Alexandre Ghiti > --- > arch/riscv/include/asm/cmpxchg.h | 35 +++++++++++++------------------- > 1 file changed, 14 insertions(+), 21 deletions(-) > > diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h > index eb35e2d30a97..0e57d5fbf227 100644 > --- a/arch/riscv/include/asm/cmpxchg.h > +++ b/arch/riscv/include/asm/cmpxchg.h > @@ -11,8 +11,8 @@ > #include > #include > > -#define __arch_xchg_masked(sc_sfx, swap_sfx, prepend, sc_append, \ > - swap_append, r, p, n) \ > +#define __arch_xchg_masked(sc_sfx, swap_sfx, sc_prepend, sc_append, \ > + r, p, n) \ > ({ \ > __label__ zabha, end; \ > \ > @@ -31,7 +31,7 @@ > ulong __rc; \ > \ > __asm__ __volatile__ ( \ > - prepend \ > + sc_prepend \ > "0: lr.w %0, %2\n" \ > " and %1, %0, %z4\n" \ > " or %1, %1, %z3\n" \ > @@ -48,9 +48,7 @@ > zabha: \ > if (IS_ENABLED(CONFIG_RISCV_ISA_ZABHA)) { \ > __asm__ __volatile__ ( \ > - prepend \ > " amoswap" swap_sfx " %0, %z2, %1\n" \ > - swap_append \ > : "=&r" (r), "+A" (*(p)) \ > : "rJ" (n) \ > : "memory"); \ > @@ -58,19 +56,17 @@ zabha: \ > end:; \ > }) > > -#define __arch_xchg(sfx, prepend, append, r, p, n) \ > +#define __arch_xchg(sfx, r, p, n) \ > ({ \ > __asm__ __volatile__ ( \ > - prepend \ > " amoswap" sfx " %0, %2, %1\n" \ > - append \ > : "=r" (r), "+A" (*(p)) \ > : "r" (n) \ > : "memory"); \ > }) > > -#define _arch_xchg(ptr, new, sc_sfx, swap_sfx, prepend, \ > - sc_append, swap_append) \ > +#define _arch_xchg(ptr, new, sc_sfx, swap_sfx, \ > + sc_prepend, sc_append) \ > ({ \ > __typeof__(ptr) __ptr = (ptr); \ > __typeof__(*(__ptr)) __new = (new); \ > @@ -79,21 +75,19 @@ end:; \ > switch (sizeof(*__ptr)) { \ > case 1: \ > __arch_xchg_masked(sc_sfx, ".b" swap_sfx, \ > - prepend, sc_append, swap_append, \ > + sc_prepend, sc_append, \ > __ret, __ptr, __new); \ > break; \ > case 2: \ > __arch_xchg_masked(sc_sfx, ".h" swap_sfx, \ > - prepend, sc_append, swap_append, \ > + sc_prepend, sc_append, \ > __ret, __ptr, __new); \ > break; \ > case 4: \ > - __arch_xchg(".w" swap_sfx, prepend, swap_append, \ > - __ret, __ptr, __new); \ > + __arch_xchg(".w" swap_sfx, __ret, __ptr, __new); \ > break; \ > case 8: \ > - __arch_xchg(".d" swap_sfx, prepend, swap_append, \ > - __ret, __ptr, __new); \ > + __arch_xchg(".d" swap_sfx, __ret, __ptr, __new); \ > break; \ > default: \ > BUILD_BUG(); \ > @@ -102,17 +96,16 @@ end:; \ > }) > > #define arch_xchg_relaxed(ptr, x) \ > - _arch_xchg(ptr, x, "", "", "", "", "") > + _arch_xchg(ptr, x, "", "", "", "") > > #define arch_xchg_acquire(ptr, x) \ > - _arch_xchg(ptr, x, "", "", "", \ > - RISCV_ACQUIRE_BARRIER, RISCV_ACQUIRE_BARRIER) > + _arch_xchg(ptr, x, "", ".aq", "", RISCV_ACQUIRE_BARRIER) > > #define arch_xchg_release(ptr, x) \ > - _arch_xchg(ptr, x, "", "", RISCV_RELEASE_BARRIER, "", "") > + _arch_xchg(ptr, x, "", ".rl", RISCV_RELEASE_BARRIER, "") > > #define arch_xchg(ptr, x) \ > - _arch_xchg(ptr, x, ".rl", ".aqrl", "", RISCV_FULL_BARRIER, "") > + _arch_xchg(ptr, x, ".rl", ".aqrl", "", RISCV_FULL_BARRIER) I actually see no reason for this patch, please see also my remarks /question on patch #4. Andrea _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv