[PATCH 1/12] generic *_bit()

Akinobu Mita
2006-01-26T03:29:18Z

This patch introduces the C-language equivalents of the functions below:

- atomic operation:
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);

- non-atomic operation:
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);

HAVE_ARCH_ATOMIC_BITOPS is defined when the architecture has its own
{,test_and_}{set,clear,change}_bit()

HAVE_ARCH_NON_ATOMIC_BITOPS is defined when the architecture has its own
__{,test_and_}{set,clear,change}_bit() and test_bit()

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

Index: 2.6-git/include/asm-generic/bitops.h
=================================--- 2.6-git.orig/include/asm-generic/bitops.h 2006-01-25 19:07:14.000000000 +0900
+++ 2.6-git/include/asm-generic/bitops.h 2006-01-25 19:14:08.000000000 +0900
@@ -1,56 +1,198 @@
#ifndef _ASM_GENERIC_BITOPS_H_
#define _ASM_GENERIC_BITOPS_H_

+#include <asm/types.h>
+
+#define BITOP_MASK(nr) (1UL << ((nr) % BITS_PER_LONG))
+#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
+
+#ifndef HAVE_ARCH_ATOMIC_BITOPS
+
+#ifdef CONFIG_SMP
+#include <asm/spinlock.h>
+#include <asm/cache.h> /* we use L1_CACHE_BYTES */
+
+/* Use an array of spinlocks for our atomic_ts.
+ * Hash function to index into a different SPINLOCK.
+ * Since "a" is usually an address, use one spinlock per cacheline.
+ */
+# define ATOMIC_HASH_SIZE 4
+# define ATOMIC_HASH(a) (&(__atomic_hash[ (((unsigned long) a)/L1_CACHE_BYTES) & (ATOMIC_HASH_SIZE-1) ]))
+
+extern raw_spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] __lock_aligned;
+
+/* Can't use raw_spin_lock_irq because of #include problems, so
+ * this is the substitute */
+#define _atomic_spin_lock_irqsave(l,f) do { \
+ raw_spinlock_t *s = ATOMIC_HASH(l); \
+ local_irq_save(f); \
+ __raw_spin_lock(s); \
+} while(0)
+
+#define _atomic_spin_unlock_irqrestore(l,f) do { \
+ raw_spinlock_t *s = ATOMIC_HASH(l); \
+ __raw_spin_unlock(s); \
+ local_irq_restore(f); \
+} while(0)
+
+
+#else
+# define _atomic_spin_lock_irqsave(l,f) do { local_irq_save(f); } while (0)
+# define _atomic_spin_unlock_irqrestore(l,f) do { local_irq_restore(f); } while (0)
+#endif
+
/*
* For the benefit of those who are trying to port Linux to another
* architecture, here are some C-language equivalents. You should
* recode these in the native assembly language, if at all possible.
- * To guarantee atomicity, these routines call cli() and sti() to
- * disable interrupts while they operate. (You have to provide inline
- * routines to cli() and sti().)
*
- * Also note, these routines assume that you have 32 bit longs.
- * You will have to change this if you are trying to port Linux to the
- * Alpha architecture or to a Cray. :-)
- *
* C language equivalents written by Theodore Ts'o, 9/26/92
*/

-extern __inline__ int set_bit(int nr,long * addr)
+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);
+ unsigned long flags;
+
+ _atomic_spin_lock_irqsave(p, flags);
+ *p |= mask;
+ _atomic_spin_unlock_irqrestore(p, flags);
+}
+
+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);
+ unsigned long flags;
+
+ _atomic_spin_lock_irqsave(p, flags);
+ *p &= ~mask;
+ _atomic_spin_unlock_irqrestore(p, flags);
+}
+
+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);
+ unsigned long flags;
+
+ _atomic_spin_lock_irqsave(p, flags);
+ *p ^= mask;
+ _atomic_spin_unlock_irqrestore(p, flags);
+}
+
+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;
+ unsigned long flags;
+
+ _atomic_spin_lock_irqsave(p, flags);
+ old = *p;
+ *p = old | mask;
+ _atomic_spin_unlock_irqrestore(p, flags);
+
+ return (old & mask) != 0;
+}
+
+static __inline__ int test_and_clear_bit(int nr, volatile unsigned long *addr)
{
- int mask, retval;
+ unsigned long mask = BITOP_MASK(nr);
+ unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);
+ unsigned long old;
+ unsigned long flags;
+
+ _atomic_spin_lock_irqsave(p, flags);
+ old = *p;
+ *p = old & ~mask;
+ _atomic_spin_unlock_irqrestore(p, flags);

- addr += nr >> 5;
- mask = 1 << (nr & 0x1f);
- cli();
- retval = (mask & *addr) != 0;
- *addr |= mask;
- sti();
- return retval;
+ return (old & mask) != 0;
}

-extern __inline__ int clear_bit(int nr, long * addr)
+static __inline__ int test_and_change_bit(int nr, volatile unsigned long *addr)
{
- int mask, retval;
+ unsigned long mask = BITOP_MASK(nr);
+ unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);
+ unsigned long old;
+ unsigned long flags;
+
+ _atomic_spin_lock_irqsave(p, flags);
+ old = *p;
+ *p = old ^ mask;
+ _atomic_spin_unlock_irqrestore(p, flags);

- addr += nr >> 5;
- mask = 1 << (nr & 0x1f);
- cli();
- retval = (mask & *addr) != 0;
- *addr &= ~mask;
- sti();
- return retval;
+ return (old & mask) != 0;
}

-extern __inline__ int test_bit(int nr, const unsigned long * addr)
+#endif /* HAVE_ARCH_ATOMIC_BITOPS */
+
+#ifndef HAVE_ARCH_NON_ATOMIC_BITOPS
+
+static __inline__ void __set_bit(int nr, volatile unsigned long *addr)
{
- int mask;
+ unsigned long mask = BITOP_MASK(nr);
+ unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);

- addr += nr >> 5;
- mask = 1 << (nr & 0x1f);
- return ((mask & *addr) != 0);
+ *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;
+}
+
+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;
+}
+
+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;
+}
+
+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;
+}
+
+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;
+}
+
+static __inline__ int test_bit(int nr, __const__ volatile unsigned long *addr)
+{
+ return 1UL & (addr[BITOP_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
+}
+
+#endif /* HAVE_ARCH_NON_ATOMIC_BITOPS */
+
/*
* fls: find last bit set.
*/