gc_locks.h

linux下的gcc编译器

#  if defined(GC_TEST_AND_SET_DEFINED) && !defined(GC_CLEAR_DEFINED)
#    ifdef __GNUC__
       inline static void GC_clear(volatile unsigned int *addr) {
         /* Try to discourage gcc from moving anything past this. */
         __asm__ __volatile__(" " : : : "memory");
         *(addr) = 0;
       }
#    else
	    /* The function call in the following should prevent the	*/
	    /* compiler from moving assignments to below the UNLOCK.	*/
#      define GC_clear(addr) GC_noop1((word)(addr)); \
			     *((volatile unsigned int *)(addr)) = 0;
#    endif
#    define GC_CLEAR_DEFINED
#  endif /* !GC_CLEAR_DEFINED */

#  if !defined(GC_TEST_AND_SET_DEFINED)
#    define USE_PTHREAD_LOCKS
#  endif

#  if defined(GC_PTHREADS) && !defined(GC_SOLARIS_THREADS) \
      && !defined(GC_IRIX_THREADS)
#    define NO_THREAD (pthread_t)(-1)
#    include <pthread.h>
#    if defined(PARALLEL_MARK) 
      /* We need compare-and-swap to update mark bits, where it's	*/
      /* performance critical.  If USE_MARK_BYTES is defined, it is	*/
      /* no longer needed for this purpose.  However we use it in	*/
      /* either case to implement atomic fetch-and-add, though that's	*/
      /* less performance critical, and could perhaps be done with	*/
      /* a lock.							*/
#     if defined(GENERIC_COMPARE_AND_SWAP)
	/* Probably not useful, except for debugging.	*/
	/* We do use GENERIC_COMPARE_AND_SWAP on PA_RISC, but we 	*/
	/* minimize its use.						*/
	extern pthread_mutex_t GC_compare_and_swap_lock;

	/* Note that if GC_word updates are not atomic, a concurrent 	*/
	/* reader should acquire GC_compare_and_swap_lock.  On 		*/
	/* currently supported platforms, such updates are atomic.	*/
	extern GC_bool GC_compare_and_exchange(volatile GC_word *addr,
					       GC_word old, GC_word new_val);
#     endif /* GENERIC_COMPARE_AND_SWAP */
#     if defined(I386)
#      if !defined(GENERIC_COMPARE_AND_SWAP)
         /* Returns TRUE if the comparison succeeded. */
         inline static GC_bool GC_compare_and_exchange(volatile GC_word *addr,
		  				       GC_word old,
						       GC_word new_val) 
         {
	   char result;
	   __asm__ __volatile__("lock; cmpxchgl %2, %0; setz %1"
	    	: "=m"(*(addr)), "=r"(result)
		: "r" (new_val), "0"(*(addr)), "a"(old) : "memory");
	   return (GC_bool) result;
         }
#      endif /* !GENERIC_COMPARE_AND_SWAP */
       inline static void GC_memory_write_barrier()
       {
	 /* We believe the processor ensures at least processor	*/
	 /* consistent ordering.  Thus a compiler barrier	*/
	 /* should suffice.					*/
         __asm__ __volatile__("" : : : "memory");
       }
#     endif /* I386 */
#     if defined(IA64)
#      if !defined(GENERIC_COMPARE_AND_SWAP)
         inline static GC_bool GC_compare_and_exchange(volatile GC_word *addr,
						       GC_word old, GC_word new_val) 
	 {
	  unsigned long oldval;
	  __asm__ __volatile__("mov ar.ccv=%4 ;; cmpxchg8.rel %0=%1,%2,ar.ccv"
		: "=r"(oldval), "=m"(*addr)
		: "r"(new_val), "1"(*addr), "r"(old) : "memory");
	  return (oldval == old);
         }
#      endif /* !GENERIC_COMPARE_AND_SWAP */
#      if 0
	/* Shouldn't be needed; we use volatile stores instead. */
        inline static void GC_memory_write_barrier()
        {
          __asm__ __volatile__("mf" : : : "memory");
        }
#      endif /* 0 */
#     endif /* IA64 */
#     if defined(S390)
#      if !defined(GENERIC_COMPARE_AND_SWAP)
	 inline static GC_bool GC_compare_and_exchange(volatile C_word *addr,
						       GC_word old, GC_word new_val) 
	 {
	   int retval;
	   __asm__ __volatile__ (
#          ifndef __s390x__
		"	cs  %1,%2,0(%3)\n"
#          else
		"	csg %1,%2,0(%3)\n"
#	   endif
		"	ipm %0\n"
		"	srl %0,28\n"
		: "=&d" (retval), "+d" (old)
		: "d" (new_val), "a" (addr)
		: "cc", "memory");
	   return retval == 0;
	}
#      endif
#     endif
#     if !defined(GENERIC_COMPARE_AND_SWAP)
        /* Returns the original value of *addr.	*/
        inline static GC_word GC_atomic_add(volatile GC_word *addr,
					    GC_word how_much)
        {
	  GC_word old;
	  do {
	    old = *addr;
	  } while (!GC_compare_and_exchange(addr, old, old+how_much));
          return old;
        }
#     else /* GENERIC_COMPARE_AND_SWAP */
	/* So long as a GC_word can be atomically updated, it should	*/
	/* be OK to read *addr without a lock.				*/
	extern GC_word GC_atomic_add(volatile GC_word *addr, GC_word how_much);
#     endif /* GENERIC_COMPARE_AND_SWAP */

#    endif /* PARALLEL_MARK */

#    if !defined(THREAD_LOCAL_ALLOC) && !defined(USE_PTHREAD_LOCKS)
      /* In the THREAD_LOCAL_ALLOC case, the allocation lock tends to	*/
      /* be held for long periods, if it is held at all.  Thus spinning	*/
      /* and sleeping for fixed periods are likely to result in 	*/
      /* significant wasted time.  We thus rely mostly on queued locks. */
#     define USE_SPIN_LOCK
      extern volatile unsigned int GC_allocate_lock;
      extern void GC_lock(void);
	/* Allocation lock holder.  Only set if acquired by client through */
	/* GC_call_with_alloc_lock.					   */
#     ifdef GC_ASSERTIONS
#        define LOCK() \
		{ if (GC_test_and_set(&GC_allocate_lock)) GC_lock(); \
		  SET_LOCK_HOLDER(); }
#        define UNLOCK() \
		{ GC_ASSERT(I_HOLD_LOCK()); UNSET_LOCK_HOLDER(); \
	          GC_clear(&GC_allocate_lock); }
#     else
#        define LOCK() \
		{ if (GC_test_and_set(&GC_allocate_lock)) GC_lock(); }
#        define UNLOCK() \
		GC_clear(&GC_allocate_lock)
#     endif /* !GC_ASSERTIONS */
#     if 0
	/* Another alternative for OSF1 might be:		*/
#       include <sys/mman.h>
        extern msemaphore GC_allocate_semaphore;
#       define LOCK() { if (msem_lock(&GC_allocate_semaphore, MSEM_IF_NOWAIT) \
 			    != 0) GC_lock(); else GC_allocate_lock = 1; }
        /* The following is INCORRECT, since the memory model is too weak. */
	/* Is this true?  Presumably msem_unlock has the right semantics?  */
	/*		- HB						   */
#       define UNLOCK() { GC_allocate_lock = 0; \
                          msem_unlock(&GC_allocate_semaphore, 0); }
#     endif /* 0 */
#    else /* THREAD_LOCAL_ALLOC  || USE_PTHREAD_LOCKS */
#      ifndef USE_PTHREAD_LOCKS
#        define USE_PTHREAD_LOCKS
#      endif
#    endif /* THREAD_LOCAL_ALLOC */
#   ifdef USE_PTHREAD_LOCKS
#      include <pthread.h>
       extern pthread_mutex_t GC_allocate_ml;
#      ifdef GC_ASSERTIONS
#        define LOCK() \
		{ GC_lock(); \
		  SET_LOCK_HOLDER(); }
#        define UNLOCK() \
		{ GC_ASSERT(I_HOLD_LOCK()); UNSET_LOCK_HOLDER(); \
	          pthread_mutex_unlock(&GC_allocate_ml); }
#      else /* !GC_ASSERTIONS */
#        define LOCK() \
	   { if (0 != pthread_mutex_trylock(&GC_allocate_ml)) GC_lock(); }
#        define UNLOCK() pthread_mutex_unlock(&GC_allocate_ml)
#      endif /* !GC_ASSERTIONS */
#   endif /* USE_PTHREAD_LOCKS */
#   define SET_LOCK_HOLDER() GC_lock_holder = pthread_self()
#   define UNSET_LOCK_HOLDER() GC_lock_holder = NO_THREAD
#   define I_HOLD_LOCK() (pthread_equal(GC_lock_holder, pthread_self()))
    extern VOLATILE GC_bool GC_collecting;
#   define ENTER_GC() GC_collecting = 1;
#   define EXIT_GC() GC_collecting = 0;
    extern void GC_lock(void);
    extern pthread_t GC_lock_holder;
#   ifdef GC_ASSERTIONS
      extern pthread_t GC_mark_lock_holder;
#   endif
#  endif /* GC_PTHREADS with linux_threads.c implementation */
#  if defined(GC_IRIX_THREADS)
#    include <pthread.h>
     /* This probably should never be included, but I can't test	*/
     /* on Irix anymore.						*/
#    include <mutex.h>

     extern unsigned long GC_allocate_lock;
	/* This is not a mutex because mutexes that obey the (optional) 	*/
	/* POSIX scheduling rules are subject to convoys in high contention	*/
	/* applications.  This is basically a spin lock.			*/
     extern pthread_t GC_lock_holder;
     extern void GC_lock(void);
	/* Allocation lock holder.  Only set if acquired by client through */
	/* GC_call_with_alloc_lock.					   */
#    define SET_LOCK_HOLDER() GC_lock_holder = pthread_self()
#    define NO_THREAD (pthread_t)(-1)
#    define UNSET_LOCK_HOLDER() GC_lock_holder = NO_THREAD
#    define I_HOLD_LOCK() (pthread_equal(GC_lock_holder, pthread_self()))
#    define LOCK() { if (GC_test_and_set(&GC_allocate_lock)) GC_lock(); }
#    define UNLOCK() GC_clear(&GC_allocate_lock);
     extern VOLATILE GC_bool GC_collecting;
#    define ENTER_GC() \
		{ \
		    GC_collecting = 1; \
		}
#    define EXIT_GC() GC_collecting = 0;
#  endif /* GC_IRIX_THREADS */
#  ifdef GC_WIN32_THREADS
#    include <windows.h>
     GC_API CRITICAL_SECTION GC_allocate_ml;
#    define LOCK() EnterCriticalSection(&GC_allocate_ml);
#    define UNLOCK() LeaveCriticalSection(&GC_allocate_ml);
#  endif
#  ifndef SET_LOCK_HOLDER
#      define SET_LOCK_HOLDER()
#      define UNSET_LOCK_HOLDER()
#      define I_HOLD_LOCK() FALSE
		/* Used on platforms were locks can be reacquired,	*/
		/* so it doesn't matter if we lie.			*/
#  endif
# else /* !THREADS */
#    define LOCK()
#    define UNLOCK()
# endif /* !THREADS */
# ifndef SET_LOCK_HOLDER
#   define SET_LOCK_HOLDER()
#   define UNSET_LOCK_HOLDER()
#   define I_HOLD_LOCK() FALSE
		/* Used on platforms were locks can be reacquired,	*/
		/* so it doesn't matter if we lie.			*/
# endif
# ifndef ENTER_GC
#   define ENTER_GC()
#   define EXIT_GC()
# endif

# ifndef DCL_LOCK_STATE
#   define DCL_LOCK_STATE
# endif
# ifndef FASTLOCK
#   define FASTLOCK() LOCK()
#   define FASTLOCK_SUCCEEDED() TRUE
#   define FASTUNLOCK() UNLOCK()
# endif

#endif /* GC_LOCKS_H */