From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 851AA33C7 for ; Wed, 18 Jan 2023 15:45:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1674056720; x=1705592720; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Z8X5newU9XL5BwcTC700iSbaht4sEux85LO6OUO0+Oc=; b=BvP0XNQHeXk6p+qln7ZGsB1KC8oCqQmaV0kVFcfMGatASB9gg/94YUEu ctk3E9Nl1OB/snlgQddHEUAFNEi5UiTWzxbHv2CijaNX0A4lSNEY4MeIG qEEpoq+ul7yQ2K7SYNYFe/qR2uQMGUpgS+W3zFiCR0tiQ8tLAb59Nthdd QdViGRN5euo7mlMyINisdkOXbmiU0yu2+GaL8nCh0jHIGPmZurkopSm5P 7bt2x3yKy4Qn9HDap48Ljp5D5C9V6gvNboG6gq1MBn6tWGiM0teSBXRwD p7M4YGENstUhXS3dLfmEu07PvGvmbyx/DJHdnzAyV8qHkKAKoRFNcUa6+ A==; X-IronPort-AV: E=McAfee;i="6500,9779,10594"; a="322701227" X-IronPort-AV: E=Sophos;i="5.97,226,1669104000"; d="scan'208";a="322701227" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jan 2023 07:45:20 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10594"; a="661759280" X-IronPort-AV: E=Sophos;i="5.97,226,1669104000"; d="scan'208";a="661759280" Received: from lab-ah.igk.intel.com ([10.102.42.211]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jan 2023 07:45:14 -0800 From: Andrzej Hajda To: linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-xtensa@linux-xtensa.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: Andrzej Hajda , Arnd Bergmann , Rodrigo Vivi , Andrew Morton , Andy Shevchenko , Peter Zijlstra , Boqun Feng , Mark Rutland Subject: [PATCH v5 2/7] linux/include: add non-atomic version of xchg Date: Wed, 18 Jan 2023 16:44:45 +0100 Message-Id: <20230118154450.73842-2-andrzej.hajda@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230118154450.73842-1-andrzej.hajda@intel.com> References: <20230118153529.57695-1-andrzej.hajda@intel.com> <20230118154450.73842-1-andrzej.hajda@intel.com> Precedence: bulk X-Mailing-List: loongarch@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Organization: Intel Technology Poland sp. z o.o. - ul. Slowackiego 173, 80-298 Gdansk - KRS 101882 - NIP 957-07-52-316 Content-Transfer-Encoding: 8bit The pattern of setting variable with new value and returning old one is very common in kernel. Usually atomicity of the operation is not required, so xchg seems to be suboptimal and confusing in such cases. Signed-off-by: Andrzej Hajda Reviewed-by: Andy Shevchenko --- include/linux/non-atomic/xchg.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) create mode 100644 include/linux/non-atomic/xchg.h diff --git a/include/linux/non-atomic/xchg.h b/include/linux/non-atomic/xchg.h new file mode 100644 index 00000000000000..f7fa5dd746f37d --- /dev/null +++ b/include/linux/non-atomic/xchg.h @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_NON_ATOMIC_XCHG_H +#define _LINUX_NON_ATOMIC_XCHG_H + +/** + * __xchg - set variable pointed by @ptr to @val, return old value + * @ptr: pointer to affected variable + * @val: value to be written + * + * This is non-atomic variant of xchg. + */ +#define __xchg(ptr, val) ({ \ + __auto_type __ptr = ptr; \ + __auto_type __t = *__ptr; \ + *__ptr = (val); \ + __t; \ +}) + +#endif -- 2.34.1