2 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
3 * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
4 * Copyright (c) 1996-1999 by Silicon Graphics. All rights reserved.
5 * Copyright (c) 1999 by Hewlett-Packard Company. All rights reserved.
8 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
9 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
11 * Permission is hereby granted to use or copy this program
12 * for any purpose, provided the above notices are retained on all copies.
13 * Permission to modify the code and to distribute modified code is granted,
14 * provided the above notices are retained, and a notice that the code was
15 * modified is included with the above copyright notice.
22 * Mutual exclusion between allocator/collector routines.
23 * Needed if there is more than one allocator thread.
24 * FASTLOCK() is assumed to try to acquire the lock in a cheap and
25 * dirty way that is acceptable for a few instructions, e.g. by
26 * inhibiting preemption. This is assumed to have succeeded only
27 * if a subsequent call to FASTLOCK_SUCCEEDED() returns TRUE.
28 * FASTUNLOCK() is called whether or not FASTLOCK_SUCCEEDED().
29 * If signals cannot be tolerated with the FASTLOCK held, then
30 * FASTLOCK should disable signals. The code executed under
31 * FASTLOCK is otherwise immune to interruption, provided it is
33 * DCL_LOCK_STATE declares any local variables needed by LOCK and UNLOCK
34 * and/or DISABLE_SIGNALS and ENABLE_SIGNALS and/or FASTLOCK.
35 * (There is currently no equivalent for FASTLOCK.)
37 * In the PARALLEL_MARK case, we also need to define a number of
38 * other inline finctions here:
39 * GC_bool GC_compare_and_exchange( volatile GC_word *addr,
40 * GC_word old, GC_word new )
41 * GC_word GC_atomic_add( volatile GC_word *addr, GC_word how_much )
42 * void GC_memory_barrier( )
46 void GC_noop1 GC_PROTO((word));
47 # ifdef PCR_OBSOLETE /* Faster, but broken with multiple lwp's */
48 # include "th/PCR_Th.h"
49 # include "th/PCR_ThCrSec.h"
50 extern struct PCR_Th_MLRep GC_allocate_ml;
51 # define DCL_LOCK_STATE PCR_sigset_t GC_old_sig_mask
52 # define LOCK() PCR_Th_ML_Acquire(&GC_allocate_ml)
53 # define UNLOCK() PCR_Th_ML_Release(&GC_allocate_ml)
54 # define UNLOCK() PCR_Th_ML_Release(&GC_allocate_ml)
55 # define FASTLOCK() PCR_ThCrSec_EnterSys()
56 /* Here we cheat (a lot): */
57 # define FASTLOCK_SUCCEEDED() (*(int *)(&GC_allocate_ml) == 0)
58 /* TRUE if nobody currently holds the lock */
59 # define FASTUNLOCK() PCR_ThCrSec_ExitSys()
62 # include <base/PCR_Base.h>
63 # include <th/PCR_Th.h>
64 extern PCR_Th_ML GC_allocate_ml;
65 # define DCL_LOCK_STATE \
66 PCR_ERes GC_fastLockRes; PCR_sigset_t GC_old_sig_mask
67 # define LOCK() PCR_Th_ML_Acquire(&GC_allocate_ml)
68 # define UNLOCK() PCR_Th_ML_Release(&GC_allocate_ml)
69 # define FASTLOCK() (GC_fastLockRes = PCR_Th_ML_Try(&GC_allocate_ml))
70 # define FASTLOCK_SUCCEEDED() (GC_fastLockRes == PCR_ERes_okay)
71 # define FASTUNLOCK() {\
72 if( FASTLOCK_SUCCEEDED() ) PCR_Th_ML_Release(&GC_allocate_ml); }
75 extern GC_word RT0u__inCritical;
76 # define LOCK() RT0u__inCritical++
77 # define UNLOCK() RT0u__inCritical--
79 # ifdef GC_SOLARIS_THREADS
82 extern mutex_t GC_allocate_ml;
83 # define LOCK() mutex_lock(&GC_allocate_ml);
84 # define UNLOCK() mutex_unlock(&GC_allocate_ml);
87 /* Try to define GC_TEST_AND_SET and a matching GC_CLEAR for spin lock */
88 /* acquisition and release. We need this for correct operation of the */
92 inline static int GC_test_and_set(volatile unsigned int *addr) {
94 /* Note: the "xchg" instruction does not need a "lock" prefix */
95 __asm__ __volatile__("xchgl %0, %1"
96 : "=r"(oldval), "=m"(*(addr))
97 : "0"(1), "m"(*(addr)) : "memory");
100 # define GC_TEST_AND_SET_DEFINED
103 # include <ia64intrin.h>
104 inline static int GC_test_and_set(volatile unsigned int *addr) {
105 return __sync_lock_test_and_set(addr, 1);
107 # define GC_TEST_AND_SET_DEFINED
108 inline static void GC_clear(volatile unsigned int *addr) {
111 # define GC_CLEAR_DEFINED
114 inline static int GC_test_and_set(volatile unsigned int *addr) {
117 __asm__ __volatile__("ldstub %1,%0"
118 : "=r"(oldval), "=m"(*addr)
119 : "m"(*addr) : "memory");
122 # define GC_TEST_AND_SET_DEFINED
125 /* Contributed by Tony Mantler. I'm not sure how well it was */
127 inline static int GC_test_and_set(volatile unsigned int *addr) {
128 char oldval; /* this must be no longer than 8 bits */
130 /* The return value is semi-phony. */
131 /* 'tas' sets bit 7 while the return */
132 /* value pretends bit 0 was set */
133 __asm__ __volatile__(
134 "tas %1@; sne %0; negb %0"
136 : "a" (addr) : "memory");
139 # define GC_TEST_AND_SET_DEFINED
141 # if defined(POWERPC)
142 inline static int GC_test_and_set(volatile unsigned int *addr) {
144 int temp = 1; // locked value
146 __asm__ __volatile__(
147 "1:\tlwarx %0,0,%3\n" // load and reserve
148 "\tcmpwi %0, 0\n" // if load is
149 "\tbne 2f\n" // non-zero, return already set
150 "\tstwcx. %2,0,%1\n" // else store conditional
151 "\tbne- 1b\n" // retry if lost reservation
152 "2:\t\n" // oldval is zero if we set
153 : "=&r"(oldval), "=p"(addr)
154 : "r"(temp), "1"(addr)
158 # define GC_TEST_AND_SET_DEFINED
159 inline static void GC_clear(volatile unsigned int *addr) {
160 __asm__ __volatile__("eieio" ::: "memory");
163 # define GC_CLEAR_DEFINED
166 inline static int GC_test_and_set(volatile unsigned int * addr)
168 unsigned long oldvalue;
171 __asm__ __volatile__(
180 ".section .text2,\"ax\"\n"
183 :"=&r" (temp), "=m" (*addr), "=&r" (oldvalue)
184 :"Ir" (1), "m" (*addr)
189 # define GC_TEST_AND_SET_DEFINED
190 /* Should probably also define GC_clear, since it needs */
191 /* a memory barrier ?? */
194 inline static int GC_test_and_set(volatile unsigned int *addr) {
196 /* SWP on ARM is very similar to XCHG on x86. Doesn't lock the
197 * bus because there are no SMP ARM machines. If/when there are,
198 * this code will likely need to be updated. */
199 /* See linuxthreads/sysdeps/arm/pt-machine.h in glibc-2.1 */
200 __asm__ __volatile__("swp %0, %1, [%2]"
206 # define GC_TEST_AND_SET_DEFINED
209 inline static int GC_test_and_set(volatile unsigned int *addr) {
211 __asm__ __volatile__ (
213 "0: cs %0,%1,0(%2)\n"
216 : "d" (1), "a" (addr)
221 # endif /* __GNUC__ */
222 # if (defined(ALPHA) && !defined(__GNUC__))
223 # define GC_test_and_set(addr) __cxx_test_and_set_atomic(addr, 1)
224 # define GC_TEST_AND_SET_DEFINED
226 # if defined(MSWIN32)
227 # define GC_test_and_set(addr) InterlockedExchange((LPLONG)addr,1)
228 # define GC_TEST_AND_SET_DEFINED
232 # include <sys/tas.h>
233 # define GC_test_and_set(addr) _test_and_set((int *) addr,1)
234 # define GC_TEST_AND_SET_DEFINED
235 # elif __mips < 3 || !(defined (_ABIN32) || defined(_ABI64)) \
236 || !defined(_COMPILER_VERSION) || _COMPILER_VERSION < 700
237 # define GC_test_and_set(addr) test_and_set(addr, 1)
239 # define GC_test_and_set(addr) __test_and_set(addr,1)
240 # define GC_clear(addr) __lock_release(addr);
241 # define GC_CLEAR_DEFINED
243 # define GC_TEST_AND_SET_DEFINED
245 # if 0 /* defined(HP_PA) */
246 /* The official recommendation seems to be to not use ldcw from */
247 /* user mode. Since multithreaded incremental collection doesn't */
248 /* work anyway on HP_PA, this shouldn't be a major loss. */
250 /* "set" means 0 and "clear" means 1 here. */
251 # define GC_test_and_set(addr) !GC_test_and_clear(addr);
252 # define GC_TEST_AND_SET_DEFINED
253 # define GC_clear(addr) GC_noop1((word)(addr)); *(volatile unsigned int *)addr = 1;
254 /* The above needs a memory barrier! */
255 # define GC_CLEAR_DEFINED
257 # if defined(GC_TEST_AND_SET_DEFINED) && !defined(GC_CLEAR_DEFINED)
259 inline static void GC_clear(volatile unsigned int *addr) {
260 /* Try to discourage gcc from moving anything past this. */
261 __asm__ __volatile__(" " : : : "memory");
265 /* The function call in the following should prevent the */
266 /* compiler from moving assignments to below the UNLOCK. */
267 # define GC_clear(addr) GC_noop1((word)(addr)); \
268 *((volatile unsigned int *)(addr)) = 0;
270 # define GC_CLEAR_DEFINED
271 # endif /* !GC_CLEAR_DEFINED */
273 # if !defined(GC_TEST_AND_SET_DEFINED)
274 # define USE_PTHREAD_LOCKS
277 # if defined(GC_PTHREADS) && !defined(GC_SOLARIS_THREADS) \
278 && !defined(GC_IRIX_THREADS)
279 # define NO_THREAD (pthread_t)(-1)
280 # include <pthread.h>
281 # if defined(PARALLEL_MARK)
282 /* We need compare-and-swap to update mark bits, where it's */
283 /* performance critical. If USE_MARK_BYTES is defined, it is */
284 /* no longer needed for this purpose. However we use it in */
285 /* either case to implement atomic fetch-and-add, though that's */
286 /* less performance critical, and could perhaps be done with */
288 # if defined(GENERIC_COMPARE_AND_SWAP)
289 /* Probably not useful, except for debugging. */
290 /* We do use GENERIC_COMPARE_AND_SWAP on PA_RISC, but we */
291 /* minimize its use. */
292 extern pthread_mutex_t GC_compare_and_swap_lock;
294 /* Note that if GC_word updates are not atomic, a concurrent */
295 /* reader should acquire GC_compare_and_swap_lock. On */
296 /* currently supported platforms, such updates are atomic. */
297 extern GC_bool GC_compare_and_exchange(volatile GC_word *addr,
298 GC_word old, GC_word new_val);
299 # endif /* GENERIC_COMPARE_AND_SWAP */
301 # if !defined(GENERIC_COMPARE_AND_SWAP)
302 /* Returns TRUE if the comparison succeeded. */
303 inline static GC_bool GC_compare_and_exchange(volatile GC_word *addr,
308 __asm__ __volatile__("lock; cmpxchgl %2, %0; setz %1"
309 : "=m"(*(addr)), "=r"(result)
310 : "r" (new_val), "0"(*(addr)), "a"(old) : "memory");
311 return (GC_bool) result;
313 # endif /* !GENERIC_COMPARE_AND_SWAP */
314 inline static void GC_memory_write_barrier()
316 /* We believe the processor ensures at least processor */
317 /* consistent ordering. Thus a compiler barrier */
318 /* should suffice. */
319 __asm__ __volatile__("" : : : "memory");
323 # if !defined(GENERIC_COMPARE_AND_SWAP)
324 inline static GC_bool GC_compare_and_exchange(volatile GC_word *addr,
328 return __sync_bool_compare_and_swap (addr, old, new_val);
330 # endif /* !GENERIC_COMPARE_AND_SWAP */
332 /* Shouldn't be needed; we use volatile stores instead. */
333 inline static void GC_memory_write_barrier()
335 __sync_synchronize ();
340 # if !defined(GENERIC_COMPARE_AND_SWAP)
341 inline static GC_bool GC_compare_and_exchange(volatile C_word *addr,
342 GC_word old, GC_word new_val)
345 __asm__ __volatile__ (
353 : "=&d" (retval), "+d" (old)
354 : "d" (new_val), "a" (addr)
360 # if !defined(GENERIC_COMPARE_AND_SWAP)
361 /* Returns the original value of *addr. */
362 inline static GC_word GC_atomic_add(volatile GC_word *addr,
368 } while (!GC_compare_and_exchange(addr, old, old+how_much));
371 # else /* GENERIC_COMPARE_AND_SWAP */
372 /* So long as a GC_word can be atomically updated, it should */
373 /* be OK to read *addr without a lock. */
374 extern GC_word GC_atomic_add(volatile GC_word *addr, GC_word how_much);
375 # endif /* GENERIC_COMPARE_AND_SWAP */
377 # endif /* PARALLEL_MARK */
379 # if !defined(THREAD_LOCAL_ALLOC) && !defined(USE_PTHREAD_LOCKS)
380 /* In the THREAD_LOCAL_ALLOC case, the allocation lock tends to */
381 /* be held for long periods, if it is held at all. Thus spinning */
382 /* and sleeping for fixed periods are likely to result in */
383 /* significant wasted time. We thus rely mostly on queued locks. */
384 # define USE_SPIN_LOCK
385 extern volatile unsigned int GC_allocate_lock;
386 extern void GC_lock(void);
387 /* Allocation lock holder. Only set if acquired by client through */
388 /* GC_call_with_alloc_lock. */
389 # ifdef GC_ASSERTIONS
391 { if (GC_test_and_set(&GC_allocate_lock)) GC_lock(); \
394 { GC_ASSERT(I_HOLD_LOCK()); UNSET_LOCK_HOLDER(); \
395 GC_clear(&GC_allocate_lock); }
398 { if (GC_test_and_set(&GC_allocate_lock)) GC_lock(); }
400 GC_clear(&GC_allocate_lock)
401 # endif /* !GC_ASSERTIONS */
403 /* Another alternative for OSF1 might be: */
404 # include <sys/mman.h>
405 extern msemaphore GC_allocate_semaphore;
406 # define LOCK() { if (msem_lock(&GC_allocate_semaphore, MSEM_IF_NOWAIT) \
407 != 0) GC_lock(); else GC_allocate_lock = 1; }
408 /* The following is INCORRECT, since the memory model is too weak. */
409 /* Is this true? Presumably msem_unlock has the right semantics? */
411 # define UNLOCK() { GC_allocate_lock = 0; \
412 msem_unlock(&GC_allocate_semaphore, 0); }
414 # else /* THREAD_LOCAL_ALLOC || USE_PTHREAD_LOCKS */
415 # ifndef USE_PTHREAD_LOCKS
416 # define USE_PTHREAD_LOCKS
418 # endif /* THREAD_LOCAL_ALLOC */
419 # ifdef USE_PTHREAD_LOCKS
420 # include <pthread.h>
421 extern pthread_mutex_t GC_allocate_ml;
422 # ifdef GC_ASSERTIONS
427 { GC_ASSERT(I_HOLD_LOCK()); UNSET_LOCK_HOLDER(); \
428 pthread_mutex_unlock(&GC_allocate_ml); }
429 # else /* !GC_ASSERTIONS */
431 { if (0 != pthread_mutex_trylock(&GC_allocate_ml)) GC_lock(); }
432 # define UNLOCK() pthread_mutex_unlock(&GC_allocate_ml)
433 # endif /* !GC_ASSERTIONS */
434 # endif /* USE_PTHREAD_LOCKS */
435 # define SET_LOCK_HOLDER() GC_lock_holder = pthread_self()
436 # define UNSET_LOCK_HOLDER() GC_lock_holder = NO_THREAD
437 # define I_HOLD_LOCK() (pthread_equal(GC_lock_holder, pthread_self()))
438 extern VOLATILE GC_bool GC_collecting;
439 # define ENTER_GC() GC_collecting = 1;
440 # define EXIT_GC() GC_collecting = 0;
441 extern void GC_lock(void);
442 extern pthread_t GC_lock_holder;
443 # ifdef GC_ASSERTIONS
444 extern pthread_t GC_mark_lock_holder;
446 # endif /* GC_PTHREADS with linux_threads.c implementation */
447 # if defined(GC_IRIX_THREADS)
448 # include <pthread.h>
449 /* This probably should never be included, but I can't test */
450 /* on Irix anymore. */
453 extern unsigned long GC_allocate_lock;
454 /* This is not a mutex because mutexes that obey the (optional) */
455 /* POSIX scheduling rules are subject to convoys in high contention */
456 /* applications. This is basically a spin lock. */
457 extern pthread_t GC_lock_holder;
458 extern void GC_lock(void);
459 /* Allocation lock holder. Only set if acquired by client through */
460 /* GC_call_with_alloc_lock. */
461 # define SET_LOCK_HOLDER() GC_lock_holder = pthread_self()
462 # define NO_THREAD (pthread_t)(-1)
463 # define UNSET_LOCK_HOLDER() GC_lock_holder = NO_THREAD
464 # define I_HOLD_LOCK() (pthread_equal(GC_lock_holder, pthread_self()))
465 # define LOCK() { if (GC_test_and_set(&GC_allocate_lock)) GC_lock(); }
466 # define UNLOCK() GC_clear(&GC_allocate_lock);
467 extern VOLATILE GC_bool GC_collecting;
468 # define ENTER_GC() \
472 # define EXIT_GC() GC_collecting = 0;
473 # endif /* GC_IRIX_THREADS */
474 # ifdef GC_WIN32_THREADS
475 # include <windows.h>
476 GC_API CRITICAL_SECTION GC_allocate_ml;
477 # define LOCK() EnterCriticalSection(&GC_allocate_ml);
478 # define UNLOCK() LeaveCriticalSection(&GC_allocate_ml);
480 # ifndef SET_LOCK_HOLDER
481 # define SET_LOCK_HOLDER()
482 # define UNSET_LOCK_HOLDER()
483 # define I_HOLD_LOCK() FALSE
484 /* Used on platforms were locks can be reacquired, */
485 /* so it doesn't matter if we lie. */
487 # else /* !THREADS */
490 # endif /* !THREADS */
491 # ifndef SET_LOCK_HOLDER
492 # define SET_LOCK_HOLDER()
493 # define UNSET_LOCK_HOLDER()
494 # define I_HOLD_LOCK() FALSE
495 /* Used on platforms were locks can be reacquired, */
496 /* so it doesn't matter if we lie. */
503 # ifndef DCL_LOCK_STATE
504 # define DCL_LOCK_STATE
507 # define FASTLOCK() LOCK()
508 # define FASTLOCK_SUCCEEDED() TRUE
509 # define FASTUNLOCK() UNLOCK()
512 #endif /* GC_LOCKS_H */