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xchg.h

#ifndef __ALPHA_SYSTEM_H
#error Do not include xchg.h directly!
#else
/*
 * xchg/xchg_local and cmpxchg/cmpxchg_local share the same code
 * except that local version do not have the expensive memory barrier.
 * So this file is included twice from asm/system.h.
 */

/*
 * Atomic exchange.
 * Since it can be used to implement critical sections
 * it must clobber "memory" (also for interrupts in UP).
 */

static inline unsigned long
____xchg(_u8, volatile char *m, unsigned long val)
{
      unsigned long ret, tmp, addr64;

      __asm__ __volatile__(
      "     andnot      %4,7,%3\n"
      "     insbl %1,%4,%1\n"
      "1:   ldq_l %2,0(%3)\n"
      "     extbl %2,%4,%0\n"
      "     mskbl %2,%4,%2\n"
      "     or    %1,%2,%2\n"
      "     stq_c %2,0(%3)\n"
      "     beq   %2,2f\n"
            __ASM__MB
      ".subsection 2\n"
      "2:   br    1b\n"
      ".previous"
      : "=&r" (ret), "=&r" (val), "=&r" (tmp), "=&r" (addr64)
      : "r" ((long)m), "1" (val) : "memory");

      return ret;
}

static inline unsigned long
____xchg(_u16, volatile short *m, unsigned long val)
{
      unsigned long ret, tmp, addr64;

      __asm__ __volatile__(
      "     andnot      %4,7,%3\n"
      "     inswl %1,%4,%1\n"
      "1:   ldq_l %2,0(%3)\n"
      "     extwl %2,%4,%0\n"
      "     mskwl %2,%4,%2\n"
      "     or    %1,%2,%2\n"
      "     stq_c %2,0(%3)\n"
      "     beq   %2,2f\n"
            __ASM__MB
      ".subsection 2\n"
      "2:   br    1b\n"
      ".previous"
      : "=&r" (ret), "=&r" (val), "=&r" (tmp), "=&r" (addr64)
      : "r" ((long)m), "1" (val) : "memory");

      return ret;
}

static inline unsigned long
____xchg(_u32, volatile int *m, unsigned long val)
{
      unsigned long dummy;

      __asm__ __volatile__(
      "1:   ldl_l %0,%4\n"
      "     bis $31,%3,%1\n"
      "     stl_c %1,%2\n"
      "     beq %1,2f\n"
            __ASM__MB
      ".subsection 2\n"
      "2:   br 1b\n"
      ".previous"
      : "=&r" (val), "=&r" (dummy), "=m" (*m)
      : "rI" (val), "m" (*m) : "memory");

      return val;
}

static inline unsigned long
____xchg(_u64, volatile long *m, unsigned long val)
{
      unsigned long dummy;

      __asm__ __volatile__(
      "1:   ldq_l %0,%4\n"
      "     bis $31,%3,%1\n"
      "     stq_c %1,%2\n"
      "     beq %1,2f\n"
            __ASM__MB
      ".subsection 2\n"
      "2:   br 1b\n"
      ".previous"
      : "=&r" (val), "=&r" (dummy), "=m" (*m)
      : "rI" (val), "m" (*m) : "memory");

      return val;
}

/* This function doesn't exist, so you'll get a linker error
   if something tries to do an invalid xchg().  */
extern void __xchg_called_with_bad_pointer(void);

static __always_inline unsigned long
____xchg(, volatile void *ptr, unsigned long x, int size)
{
      switch (size) {
            case 1:
                  return ____xchg(_u8, ptr, x);
            case 2:
                  return ____xchg(_u16, ptr, x);
            case 4:
                  return ____xchg(_u32, ptr, x);
            case 8:
                  return ____xchg(_u64, ptr, x);
      }
      __xchg_called_with_bad_pointer();
      return x;
}

/*
 * Atomic compare and exchange.  Compare OLD with MEM, if identical,
 * store NEW in MEM.  Return the initial value in MEM.  Success is
 * indicated by comparing RETURN with OLD.
 *
 * The memory barrier should be placed in SMP only when we actually
 * make the change. If we don't change anything (so if the returned
 * prev is equal to old) then we aren't acquiring anything new and
 * we don't need any memory barrier as far I can tell.
 */

static inline unsigned long
____cmpxchg(_u8, volatile char *m, unsigned char old, unsigned char new)
{
      unsigned long prev, tmp, cmp, addr64;

      __asm__ __volatile__(
      "     andnot      %5,7,%4\n"
      "     insbl %1,%5,%1\n"
      "1:   ldq_l %2,0(%4)\n"
      "     extbl %2,%5,%0\n"
      "     cmpeq %0,%6,%3\n"
      "     beq   %3,2f\n"
      "     mskbl %2,%5,%2\n"
      "     or    %1,%2,%2\n"
      "     stq_c %2,0(%4)\n"
      "     beq   %2,3f\n"
            __ASM__MB
      "2:\n"
      ".subsection 2\n"
      "3:   br    1b\n"
      ".previous"
      : "=&r" (prev), "=&r" (new), "=&r" (tmp), "=&r" (cmp), "=&r" (addr64)
      : "r" ((long)m), "Ir" (old), "1" (new) : "memory");

      return prev;
}

static inline unsigned long
____cmpxchg(_u16, volatile short *m, unsigned short old, unsigned short new)
{
      unsigned long prev, tmp, cmp, addr64;

      __asm__ __volatile__(
      "     andnot      %5,7,%4\n"
      "     inswl %1,%5,%1\n"
      "1:   ldq_l %2,0(%4)\n"
      "     extwl %2,%5,%0\n"
      "     cmpeq %0,%6,%3\n"
      "     beq   %3,2f\n"
      "     mskwl %2,%5,%2\n"
      "     or    %1,%2,%2\n"
      "     stq_c %2,0(%4)\n"
      "     beq   %2,3f\n"
            __ASM__MB
      "2:\n"
      ".subsection 2\n"
      "3:   br    1b\n"
      ".previous"
      : "=&r" (prev), "=&r" (new), "=&r" (tmp), "=&r" (cmp), "=&r" (addr64)
      : "r" ((long)m), "Ir" (old), "1" (new) : "memory");

      return prev;
}

static inline unsigned long
____cmpxchg(_u32, volatile int *m, int old, int new)
{
      unsigned long prev, cmp;

      __asm__ __volatile__(
      "1:   ldl_l %0,%5\n"
      "     cmpeq %0,%3,%1\n"
      "     beq %1,2f\n"
      "     mov %4,%1\n"
      "     stl_c %1,%2\n"
      "     beq %1,3f\n"
            __ASM__MB
      "2:\n"
      ".subsection 2\n"
      "3:   br 1b\n"
      ".previous"
      : "=&r"(prev), "=&r"(cmp), "=m"(*m)
      : "r"((long) old), "r"(new), "m"(*m) : "memory");

      return prev;
}

static inline unsigned long
____cmpxchg(_u64, volatile long *m, unsigned long old, unsigned long new)
{
      unsigned long prev, cmp;

      __asm__ __volatile__(
      "1:   ldq_l %0,%5\n"
      "     cmpeq %0,%3,%1\n"
      "     beq %1,2f\n"
      "     mov %4,%1\n"
      "     stq_c %1,%2\n"
      "     beq %1,3f\n"
            __ASM__MB
      "2:\n"
      ".subsection 2\n"
      "3:   br 1b\n"
      ".previous"
      : "=&r"(prev), "=&r"(cmp), "=m"(*m)
      : "r"((long) old), "r"(new), "m"(*m) : "memory");

      return prev;
}

/* This function doesn't exist, so you'll get a linker error
   if something tries to do an invalid cmpxchg().  */
extern void __cmpxchg_called_with_bad_pointer(void);

static __always_inline unsigned long
____cmpxchg(, volatile void *ptr, unsigned long old, unsigned long new,
            int size)
{
      switch (size) {
            case 1:
                  return ____cmpxchg(_u8, ptr, old, new);
            case 2:
                  return ____cmpxchg(_u16, ptr, old, new);
            case 4:
                  return ____cmpxchg(_u32, ptr, old, new);
            case 8:
                  return ____cmpxchg(_u64, ptr, old, new);
      }
      __cmpxchg_called_with_bad_pointer();
      return old;
}

#endif

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