[patch 05/44] generic {,test_and_}{set,clear,change}_bit()

Akinobu Mita
2006-02-01T09:13:24Z

[-- Attachment #1: atomic-bitops.patch --]
[-- Type: text/plain, Size: 6866 bytes --]

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);

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

This code largely copied from:

include/asm-powerpc/bitops.h
include/asm-parisc/bitops.h
include/asm-parisc/atomic.h

Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
include/asm-generic/bitops/atomic.h | 191 ++++++++++++++++++++++++++++++++++++
1 files changed, 191 insertions(+)

Index: 2.6-git/include/asm-generic/bitops/atomic.h
===================================================================
--- /dev/null
+++ 2.6-git/include/asm-generic/bitops/atomic.h
@@ -0,0 +1,191 @@
+#ifndef _ASM_GENERIC_BITOPS_ATOMIC_H_
+#define _ASM_GENERIC_BITOPS_ATOMIC_H_
+
+#include <asm/types.h>
+
+#define BITOP_MASK(nr) (1UL << ((nr) % BITS_PER_LONG))
+#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
+
+#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
+
+/*
+ * NMI events can occur at any time, including when interrupts have been
+ * disabled by *_irqsave(). So you can get NMI events occurring while a
+ * *_bit fucntion is holding a spin lock. If the NMI handler also wants
+ * to do bit manipulation (and they do) then you can get a deadlock
+ * between the original caller of *_bit() and the NMI handler.
+ *
+ * by Keith Owens
+ */
+
+/**
+ * set_bit - Atomically set a bit in memory
+ * @nr: the bit to set
+ * @addr: the address to start counting from
+ *
+ * This function is atomic and may not be reordered. See __set_bit()
+ * if you do not require the atomic guarantees.
+ *
+ * Note: there are no guarantees that this function will not be reordered
+ * on non x86 architectures, so if you are writting portable code,
+ * make sure not to rely on its reordering guarantees.
+ *
+ * Note that @nr may be almost arbitrarily large; this function is not
+ * restricted to acting on a single-word quantity.
+ */
+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);
+}
+
+/**
+ * clear_bit - Clears a bit in memory
+ * @nr: Bit to clear
+ * @addr: Address to start counting from
+ *
+ * clear_bit() is atomic and may not be reordered. However, it does
+ * not contain a memory barrier, so if it is used for locking purposes,
+ * you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
+ * in order to ensure changes are visible on other processors.
+ */
+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);
+}
+
+/**
+ * change_bit - Toggle a bit in memory
+ * @nr: Bit to change
+ * @addr: Address to start counting from
+ *
+ * change_bit() is atomic and may not be reordered. It may be
+ * reordered on other architectures than x86.
+ * Note that @nr may be almost arbitrarily large; this function is not
+ * restricted to acting on a single-word quantity.
+ */
+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);
+}
+
+/**
+ * test_and_set_bit - Set a bit and return its old value
+ * @nr: Bit to set
+ * @addr: Address to count from
+ *
+ * This operation is atomic and cannot be reordered.
+ * It may be reordered on other architectures than x86.
+ * It also implies a memory barrier.
+ */
+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;
+}
+
+/**
+ * test_and_clear_bit - Clear a bit and return its old value
+ * @nr: Bit to clear
+ * @addr: Address to count from
+ *
+ * This operation is atomic and cannot be reordered.
+ * It can be reorderdered on other architectures other than x86.
+ * It also implies a memory barrier.
+ */
+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;
+ unsigned long flags;
+
+ _atomic_spin_lock_irqsave(p, flags);
+ old = *p;
+ *p = old & ~mask;
+ _atomic_spin_unlock_irqrestore(p, flags);
+
+ return (old & mask) != 0;
+}
+
+/**
+ * test_and_change_bit - Change a bit and return its old value
+ * @nr: Bit to change
+ * @addr: Address to count from
+ *
+ * This operation is atomic and cannot be reordered.
+ * It also implies a memory barrier.
+ */
+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;
+ unsigned long flags;
+
+ _atomic_spin_lock_irqsave(p, flags);
+ old = *p;
+ *p = old ^ mask;
+ _atomic_spin_unlock_irqrestore(p, flags);
+
+ return (old & mask) != 0;
+}
+
+#endif /* _ASM_GENERIC_BITOPS_ATOMIC_H */

--