/*
* Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
* Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
* Copyright (c) 1996-1999 by Silicon Graphics. All rights reserved.
* Copyright (c) 1999 by Hewlett-Packard Company. All rights reserved.
*
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program
* for any purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is granted,
* provided the above notices are retained, and a notice that the code was
* modified is included with the above copyright notice.
*/
#ifndef GC_LOCKS_H
#define GC_LOCKS_H
/*
* Mutual exclusion between allocator/collector routines.
* Needed if there is more than one allocator thread.
* FASTLOCK() is assumed to try to acquire the lock in a cheap and
* dirty way that is acceptable for a few instructions, e.g. by
* inhibiting preemption. This is assumed to have succeeded only
* if a subsequent call to FASTLOCK_SUCCEEDED() returns TRUE.
* FASTUNLOCK() is called whether or not FASTLOCK_SUCCEEDED().
* If signals cannot be tolerated with the FASTLOCK held, then
* FASTLOCK should disable signals. The code executed under
* FASTLOCK is otherwise immune to interruption, provided it is
* not restarted.
* DCL_LOCK_STATE declares any local variables needed by LOCK and UNLOCK
* and/or DISABLE_SIGNALS and ENABLE_SIGNALS and/or FASTLOCK.
* (There is currently no equivalent for FASTLOCK.)
*
* In the PARALLEL_MARK case, we also need to define a number of
* other inline finctions here:
* GC_bool GC_compare_and_exchange( volatile GC_word *addr,
* GC_word old, GC_word new )
* GC_word GC_atomic_add( volatile GC_word *addr, GC_word how_much )
* void GC_memory_barrier( )
*
*/
# ifdef THREADS
void GC_noop1 GC_PROTO((word));
# ifdef PCR_OBSOLETE /* Faster, but broken with multiple lwp's */
# include "th/PCR_Th.h"
# include "th/PCR_ThCrSec.h"
extern struct PCR_Th_MLRep GC_allocate_ml;
# define DCL_LOCK_STATE PCR_sigset_t GC_old_sig_mask
# define LOCK() PCR_Th_ML_Acquire(&GC_allocate_ml)
# define UNLOCK() PCR_Th_ML_Release(&GC_allocate_ml)
# define UNLOCK() PCR_Th_ML_Release(&GC_allocate_ml)
# define FASTLOCK() PCR_ThCrSec_EnterSys()
/* Here we cheat (a lot): */
# define FASTLOCK_SUCCEEDED() (*(int *)(&GC_allocate_ml) == 0)
/* TRUE if nobody currently holds the lock */
# define FASTUNLOCK() PCR_ThCrSec_ExitSys()
# endif
# ifdef PCR
# include <base/PCR_Base.h>
# include <th/PCR_Th.h>
extern PCR_Th_ML GC_allocate_ml;
# define DCL_LOCK_STATE \
PCR_ERes GC_fastLockRes; PCR_sigset_t GC_old_sig_mask
# define LOCK() PCR_Th_ML_Acquire(&GC_allocate_ml)
# define UNLOCK() PCR_Th_ML_Release(&GC_allocate_ml)
# define FASTLOCK() (GC_fastLockRes = PCR_Th_ML_Try(&GC_allocate_ml))
# define FASTLOCK_SUCCEEDED() (GC_fastLockRes == PCR_ERes_okay)
# define FASTUNLOCK() {\
if( FASTLOCK_SUCCEEDED() ) PCR_Th_ML_Release(&GC_allocate_ml); }
# endif
# ifdef SRC_M3
extern GC_word RT0u__inCritical;
# define LOCK() RT0u__inCritical++
# define UNLOCK() RT0u__inCritical--
# endif
# ifdef SOLARIS_THREADS
# include <thread.h>
# include <signal.h>
extern mutex_t GC_allocate_ml;
# define LOCK() mutex_lock(&GC_allocate_ml);
# define UNLOCK() mutex_unlock(&GC_allocate_ml);
# endif
/* Try to define GC_TEST_AND_SET and a matching GC_CLEAR for spin lock */
/* acquisition and release. We need this for correct operation of the */
/* incremental GC. */
# ifdef __GNUC__
# if defined(I386)
inline static int GC_test_and_set(volatile unsigned int *addr) {
int oldval;
/* Note: the "xchg" instruction does not need a "lock" prefix */
__asm__ __volatile__("xchgl %0, %1"
: "=r"(oldval), "=m"(*(addr))
: "0"(1), "m"(*(addr)) : "memory");
return oldval;
}
# define GC_TEST_AND_SET_DEFINED
# endif
# if defined(IA64)
inline static int GC_test_and_set(volatile unsigned int *addr) {
long oldval, n = 1;
__asm__ __volatile__("xchg4 %0=%1,%2"
: "=r"(oldval), "=m"(*addr)
: "r"(n), "1"(*addr) : "memory");
return oldval;
}
# define GC_TEST_AND_SET_DEFINED
/* Should this handle post-increment addressing?? */
inline static void GC_clear(volatile unsigned int *addr) {
__asm__ __volatile__("st4.rel %0=r0" : "=m" (*addr) : : "memory");
}
# define GC_CLEAR_DEFINED
# endif
# ifdef SPARC
inline static int GC_test_and_set(volatile unsigned int *addr) {
int oldval;
__asm__ __volatile__("ldstub %1,%0"
: "=r"(oldval), "=m"(*addr)
: "m"(*addr) : "memory");
return oldval;
}
# define GC_TEST_AND_SET_DEFINED
# endif
# ifdef M68K
/* Contributed by Tony Mantler. I'm not sure how well it was */
/* tested. */
inline static int GC_test_and_set(volatile unsigned int *addr) {
char oldval; /* this must be no longer than 8 bits */
/* The return value is semi-phony. */
/* 'tas' sets bit 7 while the return */
/* value pretends bit 0 was set */
__asm__ __volatile__(
"tas %1@; sne %0; negb %0"
: "=d" (oldval)
: "a" (addr) : "memory");
return oldval;
}
# define GC_TEST_AND_SET_DEFINED
# endif
# if defined(POWERPC)
inline static int GC_test_and_set(volatile unsigned int *addr) {
int oldval;
int temp = 1; // locked value
__asm__ __volatile__(
"1:\tlwarx %0,0,%3\n" // load and reserve
"\tcmpwi %0, 0\n" // if load is
"\tbne 2f\n" // non-zero, return already set
"\tstwcx. %2,0,%1\n" // else store conditional
"\tbne- 1b\n" // retry if lost reservation
"2:\t\n" // oldval is zero if we set
: "=&r"(oldval), "=p"(addr)
: "r"(temp), "1"(addr)
: "memory");
return (int)oldval;
}
# define GC_TEST_AND_SET_DEFINED
inline static void GC_clear(volatile unsigned int *addr) {
__asm__ __volatile__("eieio" ::: "memory");
*(addr) = 0;
}
# define GC_CLEAR_DEFINED
# endif
# if defined(ALPHA)
inline static int GC_test_and_set(volatile unsigned int * addr)
{
unsigned long oldvalue;
unsigned long temp;
__asm__ __volatile__(
"1: ldl_l %0,%1\n"
" and %0,%3,%2\n"
" bne %2,2f\n"
" xor %0,%3,%0\n"
" stl_c %0,%1\n"
" beq %0,3f\n"
" mb\n"
"2:\n"
".section .text2,\"ax\"\n"
"3: br 1b\n"
".previous"
:"=&r" (temp), "=m" (*addr), "=&r" (oldvalue)
:"Ir" (1), "m" (*addr)
:"memory");
return oldvalue;
}
# define GC_TEST_AND_SET_DEFINED
/* Should probably also define GC_clear, since it needs */
/* a memory barrier ?? */
# endif /* ALPHA */
# ifdef ARM32
inline static int GC_test_and_set(volatile unsigned int *addr) {
int oldval;
/* SWP on ARM is very similar to XCHG on x86. Doesn't lock the
* bus because there are no SMP ARM machines. If/when there are,
* this code will likely need to be updated. */
/* See linuxthreads/sysdeps/arm/pt-machine.h in glibc-2.1 */
__asm__ __volatile__("swp %0, %1, [%2]"
: "=r"(oldval)
: "r"(1), "r"(addr)
: "memory");
return oldval;
}
# define GC_TEST_AND_SET_DEFINED
# endif /* ARM32 */
# endif /* __GNUC__ */
# if (defined(ALPHA) && !defined(__GNUC__))
# define GC_test_and_set(addr) __cxx_test_and_set_atomic(addr, 1)
# define GC_TEST_AND_SET_DEFINED
# endif
# if defined(MSWIN32)
# define GC_test_and_set(addr) InterlockedExchange((LPLONG)addr,1)
# define GC_TEST_AND_SET_DEFINED
# endif
# ifdef MIPS
# if __mips < 3 || !(defined (_ABIN32) || defined(_ABI64)) \
|| !defined(_COMPILER_VERSION) || _COMPILER_VERSION < 700
# define GC_test_and_set(addr, v) test_and_set(addr,v)
# else
# define GC_test_and_set(addr, v) __test_and_set(addr,v)
# define GC_clear(addr) __lock_release(addr);
# define GC_CLEAR_DEFINED
# endif
# define GC_TEST_AND_SET_DEFINED
# endif /* MIPS */
# if 0 /* defined(HP_PA) */
/* The official recommendation seems to be to not use ldcw from */
/* user mode. Since multithreaded incremental collection doesn't */
/* work anyway on HP_PA, this shouldn't be a major loss. */
/* "set" means 0 and "clear" means 1 here. */
# define GC_test_and_set(addr) !GC_test_and_clear(addr);
# define GC_TEST_AND_SET_DEFINED
# define GC_clear(addr) GC_noop1((word)(addr)); *(volatile unsigned int *)addr = 1;
/* The above needs a memory barrier! */
# define GC_CLEAR_DEFINED
# endif
# 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(LINUX_THREADS) || defined(OSF1_THREADS) \
|| defined(HPUX_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(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 /* LINUX_THREADS || OSF1_THREADS || HPUX_THREADS */
# if defined(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, 1)) 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 /* IRIX_THREADS */
# ifdef 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 */
