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[patch 06/44] generic __{,test_and_}{set,clear,change}_bit() and test_bi

To: linux-kernel@vger.kernel.org
Subject: [patch 06/44] generic __{,test_and_}{set,clear,change}_bit() and test_bit()
From: Akinobu Mita <mita@miraclelinux.com>
Date: Wed, 01 Feb 2006 18:02:30 +0900
Cc: Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Russell King <rmk@arm.linux.org.uk>, Ian Molton <spyro@f2s.com>, dev-etrax@axis.com, linux-ia64@vger.kernel.org, Hirokazu Takata <takata@linux-m32r.org>, linux-mips@linux-mips.org, parisc-linux@parisc-linux.org, linuxppc-dev@ozlabs.org, linuxsh-dev@lists.sourceforge.net, linuxsh-shmedia-dev@lists.sourceforge.net, sparclinux@vger.kernel.org, ultralinux@vger.kernel.org, Chris Zankel <chris@zankel.net>, Akinobu Mita <mita@miraclelinux.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20060201090224.536581000@localhost.localdomain>
Sender: linux-mips-bounce@linux-mips.org
This patch introduces the C-language equivalents of the functions below:

void __set_bit(int nr, volatile unsigned long *addr);
void __clear_bit(int nr, volatile unsigned long *addr);
void __change_bit(int nr, volatile unsigned long *addr);
int __test_and_set_bit(int nr, volatile unsigned long *addr);
int __test_and_clear_bit(int nr, volatile unsigned long *addr);
int __test_and_change_bit(int nr, volatile unsigned long *addr);
int test_bit(int nr, const volatile unsigned long *addr);

In include/asm-generic/bitops/non-atomic.h

This code largely copied from:
asm-powerpc/bitops.h

Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
 include/asm-generic/bitops/non-atomic.h |  111 ++++++++++++++++++++++++++++++++
 1 files changed, 111 insertions(+)

Index: 2.6-git/include/asm-generic/bitops/non-atomic.h
===================================================================
--- /dev/null
+++ 2.6-git/include/asm-generic/bitops/non-atomic.h
@@ -0,0 +1,111 @@
+#ifndef _ASM_GENERIC_BITOPS_NON_ATOMIC_H_
+#define _ASM_GENERIC_BITOPS_NON_ATOMIC_H_
+
+#include <asm/types.h>
+
+#define BITOP_MASK(nr)         (1UL << ((nr) % BITS_PER_LONG))
+#define BITOP_WORD(nr)         ((nr) / BITS_PER_LONG)
+
+/**
+ * __set_bit - Set a bit in memory
+ * @nr: the bit to set
+ * @addr: the address to start counting from
+ *
+ * Unlike set_bit(), this function is non-atomic and may be reordered.
+ * If it's called on the same region of memory simultaneously, the effect
+ * may be that only one operation succeeds.
+ */
+static __inline__ void __set_bit(int nr, volatile unsigned long *addr)
+{
+       unsigned long mask = BITOP_MASK(nr);
+       unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);
+
+       *p  |= mask;
+}
+
+static __inline__ void __clear_bit(int nr, volatile unsigned long *addr)
+{
+       unsigned long mask = BITOP_MASK(nr);
+       unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);
+
+       *p &= ~mask;
+}
+
+/**
+ * __change_bit - Toggle a bit in memory
+ * @nr: the bit to change
+ * @addr: the address to start counting from
+ *
+ * Unlike change_bit(), this function is non-atomic and may be reordered.
+ * If it's called on the same region of memory simultaneously, the effect
+ * may be that only one operation succeeds.
+ */
+static __inline__ void __change_bit(int nr, volatile unsigned long *addr)
+{
+       unsigned long mask = BITOP_MASK(nr);
+       unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);
+
+       *p ^= mask;
+}
+
+/**
+ * __test_and_set_bit - Set a bit and return its old value
+ * @nr: Bit to set
+ * @addr: Address to count from
+ *
+ * This operation is non-atomic and can be reordered.  
+ * If two examples of this operation race, one can appear to succeed
+ * but actually fail.  You must protect multiple accesses with a lock.
+ */
+static __inline__ int __test_and_set_bit(int nr, volatile unsigned long *addr)
+{
+       unsigned long mask = BITOP_MASK(nr);
+       unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);
+       unsigned long old = *p;
+
+       *p = old | mask;
+       return (old & mask) != 0;
+}
+
+/**
+ * __test_and_clear_bit - Clear a bit and return its old value
+ * @nr: Bit to clear
+ * @addr: Address to count from
+ *
+ * This operation is non-atomic and can be reordered.  
+ * If two examples of this operation race, one can appear to succeed
+ * but actually fail.  You must protect multiple accesses with a lock.
+ */
+static __inline__ int __test_and_clear_bit(int nr, volatile unsigned long 
*addr)
+{
+       unsigned long mask = BITOP_MASK(nr);
+       unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);
+       unsigned long old = *p;
+
+       *p = old & ~mask;
+       return (old & mask) != 0;
+}
+
+/* WARNING: non atomic and it can be reordered! */
+static __inline__ int __test_and_change_bit(int nr,
+                                           volatile unsigned long *addr)
+{
+       unsigned long mask = BITOP_MASK(nr);
+       unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);
+       unsigned long old = *p;
+
+       *p = old ^ mask;
+       return (old & mask) != 0;
+}
+
+/**
+ * test_bit - Determine whether a bit is set
+ * @nr: bit number to test
+ * @addr: Address to start counting from
+ */
+static __inline__ int test_bit(int nr, __const__ volatile unsigned long *addr)
+{
+       return 1UL & (addr[BITOP_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
+}
+
+#endif /* _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ */

--

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