atomic_bsd_zero.hpp

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 * Copyright 2007, 2008, 2011, 2015, Red Hat, Inc.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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#ifndef OS_CPU_BSD_ZERO_ATOMIC_BSD_ZERO_HPP
#define OS_CPU_BSD_ZERO_ATOMIC_BSD_ZERO_HPP

#include "orderAccess_bsd_zero.hpp"
#include "runtime/os.hpp"

// Implementation of class atomic

#ifdef M68K

/*
 * __m68k_cmpxchg
 *
 * Atomically store newval in *ptr if *ptr is equal to oldval for user space.
 * Returns newval on success and oldval if no exchange happened.
 * This implementation is processor specific and works on
 * 68020 68030 68040 and 68060.
 *
 * It will not work on ColdFire, 68000 and 68010 since they lack the CAS
 * instruction.
 * Using a kernelhelper would be better for arch complete implementation.
 *
 */

static inline int __m68k_cmpxchg(int oldval, int newval, volatile int *ptr) {
  int ret;
  __asm __volatile ("cas%.l %0,%2,%1"
                   : "=d" (ret), "+m" (*(ptr))
                   : "d" (newval), "0" (oldval));
  return ret;
}

/* Perform an atomic compare and swap: if the current value of `*PTR'
   is OLDVAL, then write NEWVAL into `*PTR'.  Return the contents of
   `*PTR' before the operation.*/
static inline int m68k_compare_and_swap(int newval,
                                        volatile int *ptr,
                                        int oldval) {
  for (;;) {
      int prev = *ptr;
      if (prev != oldval)
        return prev;

      if (__m68k_cmpxchg (prev, newval, ptr) == newval)
        // Success.
        return prev;

      // We failed even though prev == oldval.  Try again.
    }
}

/* Atomically add an int to memory.  */
static inline int m68k_add_and_fetch(int add_value, volatile int *ptr) {
  for (;;) {
      // Loop until success.

      int prev = *ptr;

      if (__m68k_cmpxchg (prev, prev + add_value, ptr) == prev + add_value)
        return prev + add_value;
    }
}

/* Atomically write VALUE into `*PTR' and returns the previous
   contents of `*PTR'.  */
static inline int m68k_lock_test_and_set(int newval, volatile int *ptr) {
  for (;;) {
      // Loop until success.
      int prev = *ptr;

      if (__m68k_cmpxchg (prev, newval, ptr) == prev)
        return prev;
    }
}
#endif // M68K

#ifdef ARM

/*
 * __kernel_cmpxchg
 *
 * Atomically store newval in *ptr if *ptr is equal to oldval for user space.
 * Return zero if *ptr was changed or non-zero if no exchange happened.
 * The C flag is also set if *ptr was changed to allow for assembly
 * optimization in the calling code.
 *
 */

typedef int (__kernel_cmpxchg_t)(int oldval, int newval, volatile int *ptr);
#define __kernel_cmpxchg (*(__kernel_cmpxchg_t *) 0xffff0fc0)



/* Perform an atomic compare and swap: if the current value of `*PTR'
   is OLDVAL, then write NEWVAL into `*PTR'.  Return the contents of
   `*PTR' before the operation.*/
static inline int arm_compare_and_swap(int newval,
                                       volatile int *ptr,
                                       int oldval) {
  for (;;) {
      int prev = *ptr;
      if (prev != oldval)
        return prev;

      if (__kernel_cmpxchg (prev, newval, ptr) == 0)
        // Success.
        return prev;

      // We failed even though prev == oldval.  Try again.
    }
}

/* Atomically add an int to memory.  */
static inline int arm_add_and_fetch(int add_value, volatile int *ptr) {
  for (;;) {
      // Loop until a __kernel_cmpxchg succeeds.

      int prev = *ptr;

      if (__kernel_cmpxchg (prev, prev + add_value, ptr) == 0)
        return prev + add_value;
    }
}

/* Atomically write VALUE into `*PTR' and returns the previous
   contents of `*PTR'.  */
static inline int arm_lock_test_and_set(int newval, volatile int *ptr) {
  for (;;) {
      // Loop until a __kernel_cmpxchg succeeds.
      int prev = *ptr;

      if (__kernel_cmpxchg (prev, newval, ptr) == 0)
        return prev;
    }
}
#endif // ARM

template<size_t byte_size>
struct Atomic::PlatformAdd {
  template<typename D, typename I>
  D add_and_fetch(D volatile* dest, I add_value, atomic_memory_order order) const;

  template<typename D, typename I>
  D fetch_and_add(D volatile* dest, I add_value, atomic_memory_order order) const {
    return add_and_fetch(dest, add_value, order) - add_value;
  }
};

template<>
template<typename D, typename I>
inline D Atomic::PlatformAdd<4>::add_and_fetch(D volatile* dest, I add_value,
                                               atomic_memory_order order) const {
  STATIC_ASSERT(4 == sizeof(I));
  STATIC_ASSERT(4 == sizeof(D));

#ifdef ARM
  return add_using_helper<int>(arm_add_and_fetch, dest, add_value);
#else
#ifdef M68K
  return add_using_helper<int>(m68k_add_and_fetch, dest, add_value);
#else
  D res = __atomic_add_fetch(dest, add_value, __ATOMIC_RELEASE);
  FULL_MEM_BARRIER;
  return res;
#endif // M68K
#endif // ARM
}

template<>
template<typename D, typename I>
inline D Atomic::PlatformAdd<8>::add_and_fetch(D volatile* dest, I add_value,
                                               atomic_memory_order order) const {
  STATIC_ASSERT(8 == sizeof(I));
  STATIC_ASSERT(8 == sizeof(D));

  D res = __atomic_add_fetch(dest, add_value, __ATOMIC_RELEASE);
  FULL_MEM_BARRIER;
  return res;
}

template<>
template<typename T>
inline T Atomic::PlatformXchg<4>::operator()(T volatile* dest,
                                             T exchange_value,
                                             atomic_memory_order order) const {
  STATIC_ASSERT(4 == sizeof(T));
#ifdef ARM
  return xchg_using_helper<int>(arm_lock_test_and_set, dest, exchange_value);
#else
#ifdef M68K
  return xchg_using_helper<int>(m68k_lock_test_and_set, dest, exchange_value);
#else
  // __sync_lock_test_and_set is a bizarrely named atomic exchange
  // operation.  Note that some platforms only support this with the
  // limitation that the only valid value to store is the immediate
  // constant 1.  There is a test for this in JNI_CreateJavaVM().
  T result = __sync_lock_test_and_set (dest, exchange_value);
  // All atomic operations are expected to be full memory barriers
  // (see atomic.hpp). However, __sync_lock_test_and_set is not
  // a full memory barrier, but an acquire barrier. Hence, this added
  // barrier. Some platforms (notably ARM) have peculiarities with
  // their barrier implementations, delegate it to OrderAccess.
  OrderAccess::fence();
  return result;
#endif // M68K
#endif // ARM
}

template<>
template<typename T>
inline T Atomic::PlatformXchg<8>::operator()(T volatile* dest,
                                             T exchange_value,
                                             atomic_memory_order order) const {
  STATIC_ASSERT(8 == sizeof(T));
  T result = __sync_lock_test_and_set (dest, exchange_value);
  OrderAccess::fence();
  return result;
}

// No direct support for cmpxchg of bytes; emulate using int.
template<>
struct Atomic::PlatformCmpxchg<1> : Atomic::CmpxchgByteUsingInt {};

template<>
template<typename T>
inline T Atomic::PlatformCmpxchg<4>::operator()(T volatile* dest,
                                                T compare_value,
                                                T exchange_value,
                                                atomic_memory_order order) const {
  STATIC_ASSERT(4 == sizeof(T));
#ifdef ARM
  return cmpxchg_using_helper<int>(arm_compare_and_swap, dest, compare_value, exchange_value);
#else
#ifdef M68K
  return cmpxchg_using_helper<int>(m68k_compare_and_swap, dest, compare_value, exchange_value);
#else
  T value = compare_value;
  FULL_MEM_BARRIER;
  __atomic_compare_exchange(dest, &value, &exchange_value, /*weak*/false,
                            __ATOMIC_RELAXED, __ATOMIC_RELAXED);
  FULL_MEM_BARRIER;
  return value;
#endif // M68K
#endif // ARM
}

template<>
template<typename T>
inline T Atomic::PlatformCmpxchg<8>::operator()(T volatile* dest,
                                                T compare_value,
                                                T exchange_value,
                                                atomic_memory_order order) const {
  STATIC_ASSERT(8 == sizeof(T));

  T value = compare_value;
  FULL_MEM_BARRIER;
  __atomic_compare_exchange(dest, &value, &exchange_value, /*weak*/false,
                            __ATOMIC_RELAXED, __ATOMIC_RELAXED);
  FULL_MEM_BARRIER;
  return value;
}

template<>
template<typename T>
inline T Atomic::PlatformLoad<8>::operator()(T const volatile* src) const {
  STATIC_ASSERT(8 == sizeof(T));
  volatile int64_t dest;
  os::atomic_copy64(reinterpret_cast<const volatile int64_t*>(src), reinterpret_cast<volatile int64_t*>(&dest));
  return PrimitiveConversions::cast<T>(dest);
}

template<>
template<typename T>
inline void Atomic::PlatformStore<8>::operator()(T volatile* dest,
                                                 T store_value) const {
  STATIC_ASSERT(8 == sizeof(T));
  os::atomic_copy64(reinterpret_cast<const volatile int64_t*>(&store_value), reinterpret_cast<volatile int64_t*>(dest));
}

#endif // OS_CPU_BSD_ZERO_ATOMIC_BSD_ZERO_HPP