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From: Andrzej Hajda <andrzej.hajda@intel.com>
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,
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	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 <andrzej.hajda@intel.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Boqun Feng <boqun.feng@gmail.com>,
	Mark Rutland <mark.rutland@arm.com>
Subject: [PATCH v5 2/7] linux/include: add non-atomic version of xchg
Date: Wed, 18 Jan 2023 15:44:45 +0000	[thread overview]
Message-ID: <20230118154450.73842-2-andrzej.hajda@intel.com> (raw)
In-Reply-To: <20230118154450.73842-1-andrzej.hajda@intel.com>

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 <andrzej.hajda@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 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

  reply	other threads:[~2023-01-18 15:44 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-18 15:35 [PATCH v5 0/7] Introduce __xchg, non-atomic xchg Andrzej Hajda
2023-01-18 15:44 ` [PATCH v5 1/7] arch: rename all internal names __xchg to __arch_xchg Andrzej Hajda
2023-01-18 15:44   ` Andrzej Hajda [this message]
2023-02-27  9:53     ` [Intel-gfx] [PATCH v5 2/7] linux/include: add non-atomic version of xchg Andi Shyti
2023-01-18 15:44   ` [PATCH v5 3/7] arch/*/uprobes: simplify arch_uretprobe_hijack_return_addr Andrzej Hajda
2023-02-27  9:54     ` [Intel-gfx] " Andi Shyti
2023-01-18 15:44   ` [PATCH v5 4/7] llist: simplify __llist_del_all Andrzej Hajda
2023-02-27  9:55     ` [Intel-gfx] " Andi Shyti
2023-01-18 15:44   ` [PATCH v5 5/7] io_uring: use __xchg if possible Andrzej Hajda
2023-02-27  9:59     ` [Intel-gfx] " Andi Shyti
2023-01-18 15:44   ` [PATCH v5 6/7] qed: " Andrzej Hajda
2023-02-27  9:56     ` [Intel-gfx] " Andi Shyti
2023-01-18 15:44   ` [PATCH v5 7/7] drm/i915/gt: use __xchg instead of internal helper Andrzej Hajda
2023-02-27  9:58     ` [Intel-gfx] " Andi Shyti
2023-02-27  9:53   ` [Intel-gfx] [PATCH v5 1/7] arch: rename all internal names __xchg to __arch_xchg Andi Shyti
2023-02-22 10:36 ` [Intel-gfx] [PATCH v5 0/7] Introduce __xchg, non-atomic xchg Andrzej Hajda
2023-02-22 17:04 ` Peter Zijlstra
2023-02-23 21:24   ` [Intel-gfx] " Andrzej Hajda
2023-02-27 13:49     ` Peter Zijlstra
2024-04-05 14:47       ` Jani Nikula
2024-04-05 16:20         ` Andrzej Hajda

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