From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrzej Hajda Date: Wed, 18 Jan 2023 15:44:45 +0000 Subject: [PATCH v5 2/7] linux/include: add non-atomic version of xchg Message-Id: <20230118154450.73842-2-andrzej.hajda@intel.com> List-Id: References: <20230118153529.57695-1-andrzej.hajda@intel.com> <20230118154450.73842-1-andrzej.hajda@intel.com> In-Reply-To: <20230118154450.73842-1-andrzej.hajda@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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 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