1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team, 1998-2008
5 * Storage manager front end
7 * Documentation on the architecture of the Storage Manager can be
8 * found in the online commentary:
10 * http://hackage.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage
12 * ---------------------------------------------------------------------------*/
14 #include "PosixSource.h"
21 #include "BlockAlloc.h"
25 #include "Capability.h"
27 #include "RetainerProfile.h" // for counting memory blocks (memInventory)
38 * All these globals require sm_mutex to access in THREADED_RTS mode.
40 StgClosure *caf_list = NULL;
41 StgClosure *revertible_caf_list = NULL;
44 nat large_alloc_lim; /* GC if n_large_blocks in any nursery
49 generation *generations = NULL; /* all the generations */
50 generation *g0 = NULL; /* generation 0, for convenience */
51 generation *oldest_gen = NULL; /* oldest generation, for convenience */
53 nursery *nurseries = NULL; /* array of nurseries, size == n_capabilities */
57 * Storage manager mutex: protects all the above state from
58 * simultaneous access by two STG threads.
63 static void allocNurseries ( void );
66 initGeneration (generation *gen, int g)
70 gen->par_collections = 0;
71 gen->failed_promotions = 0;
76 gen->live_estimate = 0;
77 gen->old_blocks = NULL;
78 gen->n_old_blocks = 0;
79 gen->large_objects = NULL;
80 gen->n_large_blocks = 0;
81 gen->n_new_large_words = 0;
82 gen->scavenged_large_objects = NULL;
83 gen->n_scavenged_large_blocks = 0;
88 initSpinLock(&gen->sync);
90 gen->threads = END_TSO_QUEUE;
91 gen->old_threads = END_TSO_QUEUE;
99 if (generations != NULL) {
100 // multi-init protection
106 /* Sanity check to make sure the LOOKS_LIKE_ macros appear to be
107 * doing something reasonable.
109 /* We use the NOT_NULL variant or gcc warns that the test is always true */
110 ASSERT(LOOKS_LIKE_INFO_PTR_NOT_NULL((StgWord)&stg_BLOCKING_QUEUE_CLEAN_info));
111 ASSERT(LOOKS_LIKE_CLOSURE_PTR(&stg_dummy_ret_closure));
112 ASSERT(!HEAP_ALLOCED(&stg_dummy_ret_closure));
114 if (RtsFlags.GcFlags.maxHeapSize != 0 &&
115 RtsFlags.GcFlags.heapSizeSuggestion >
116 RtsFlags.GcFlags.maxHeapSize) {
117 RtsFlags.GcFlags.maxHeapSize = RtsFlags.GcFlags.heapSizeSuggestion;
120 if (RtsFlags.GcFlags.maxHeapSize != 0 &&
121 RtsFlags.GcFlags.minAllocAreaSize >
122 RtsFlags.GcFlags.maxHeapSize) {
123 errorBelch("maximum heap size (-M) is smaller than minimum alloc area size (-A)");
124 RtsFlags.GcFlags.minAllocAreaSize = RtsFlags.GcFlags.maxHeapSize;
127 initBlockAllocator();
129 #if defined(THREADED_RTS)
130 initMutex(&sm_mutex);
135 /* allocate generation info array */
136 generations = (generation *)stgMallocBytes(RtsFlags.GcFlags.generations
137 * sizeof(struct generation_),
138 "initStorage: gens");
140 /* Initialise all generations */
141 for(g = 0; g < RtsFlags.GcFlags.generations; g++) {
142 initGeneration(&generations[g], g);
145 /* A couple of convenience pointers */
146 g0 = &generations[0];
147 oldest_gen = &generations[RtsFlags.GcFlags.generations-1];
149 nurseries = stgMallocBytes(n_capabilities * sizeof(struct nursery_),
150 "initStorage: nurseries");
152 /* Set up the destination pointers in each younger gen. step */
153 for (g = 0; g < RtsFlags.GcFlags.generations-1; g++) {
154 generations[g].to = &generations[g+1];
156 oldest_gen->to = oldest_gen;
158 /* The oldest generation has one step. */
159 if (RtsFlags.GcFlags.compact || RtsFlags.GcFlags.sweep) {
160 if (RtsFlags.GcFlags.generations == 1) {
161 errorBelch("WARNING: compact/sweep is incompatible with -G1; disabled");
163 oldest_gen->mark = 1;
164 if (RtsFlags.GcFlags.compact)
165 oldest_gen->compact = 1;
169 generations[0].max_blocks = 0;
171 /* The allocation area. Policy: keep the allocation area
172 * small to begin with, even if we have a large suggested heap
173 * size. Reason: we're going to do a major collection first, and we
174 * don't want it to be a big one. This vague idea is borne out by
175 * rigorous experimental evidence.
179 weak_ptr_list = NULL;
180 caf_list = END_OF_STATIC_LIST;
181 revertible_caf_list = END_OF_STATIC_LIST;
183 /* initialise the allocate() interface */
184 large_alloc_lim = RtsFlags.GcFlags.minAllocAreaSize * BLOCK_SIZE_W;
189 initSpinLock(&gc_alloc_block_sync);
195 // allocate a block for each mut list
196 for (n = 0; n < n_capabilities; n++) {
197 for (g = 1; g < RtsFlags.GcFlags.generations; g++) {
198 capabilities[n].mut_lists[g] = allocBlock();
204 IF_DEBUG(gc, statDescribeGens());
212 stat_exit(calcAllocated(rtsTrue));
216 freeStorage (rtsBool free_heap)
218 stgFree(generations);
219 if (free_heap) freeAllMBlocks();
220 #if defined(THREADED_RTS)
221 closeMutex(&sm_mutex);
227 /* -----------------------------------------------------------------------------
230 The entry code for every CAF does the following:
232 - builds a BLACKHOLE in the heap
233 - pushes an update frame pointing to the BLACKHOLE
234 - calls newCaf, below
235 - updates the CAF with a static indirection to the BLACKHOLE
237 Why do we build an BLACKHOLE in the heap rather than just updating
238 the thunk directly? It's so that we only need one kind of update
239 frame - otherwise we'd need a static version of the update frame too.
241 newCaf() does the following:
243 - it puts the CAF on the oldest generation's mutable list.
244 This is so that we treat the CAF as a root when collecting
247 For GHCI, we have additional requirements when dealing with CAFs:
249 - we must *retain* all dynamically-loaded CAFs ever entered,
250 just in case we need them again.
251 - we must be able to *revert* CAFs that have been evaluated, to
252 their pre-evaluated form.
254 To do this, we use an additional CAF list. When newCaf() is
255 called on a dynamically-loaded CAF, we add it to the CAF list
256 instead of the old-generation mutable list, and save away its
257 old info pointer (in caf->saved_info) for later reversion.
259 To revert all the CAFs, we traverse the CAF list and reset the
260 info pointer to caf->saved_info, then throw away the CAF list.
261 (see GC.c:revertCAFs()).
265 -------------------------------------------------------------------------- */
268 newCAF(StgRegTable *reg, StgClosure* caf)
273 // If we are in GHCi _and_ we are using dynamic libraries,
274 // then we can't redirect newCAF calls to newDynCAF (see below),
275 // so we make newCAF behave almost like newDynCAF.
276 // The dynamic libraries might be used by both the interpreted
277 // program and GHCi itself, so they must not be reverted.
278 // This also means that in GHCi with dynamic libraries, CAFs are not
279 // garbage collected. If this turns out to be a problem, we could
280 // do another hack here and do an address range test on caf to figure
281 // out whether it is from a dynamic library.
282 ((StgIndStatic *)caf)->saved_info = (StgInfoTable *)caf->header.info;
284 ACQUIRE_SM_LOCK; // caf_list is global, locked by sm_mutex
285 ((StgIndStatic *)caf)->static_link = caf_list;
291 // Put this CAF on the mutable list for the old generation.
292 ((StgIndStatic *)caf)->saved_info = NULL;
293 if (oldest_gen->no != 0) {
294 recordMutableCap(caf, regTableToCapability(reg), oldest_gen->no);
299 // External API for setting the keepCAFs flag. see #3900.
306 // An alternate version of newCaf which is used for dynamically loaded
307 // object code in GHCi. In this case we want to retain *all* CAFs in
308 // the object code, because they might be demanded at any time from an
309 // expression evaluated on the command line.
310 // Also, GHCi might want to revert CAFs, so we add these to the
311 // revertible_caf_list.
313 // The linker hackily arranges that references to newCaf from dynamic
314 // code end up pointing to newDynCAF.
316 newDynCAF (StgRegTable *reg STG_UNUSED, StgClosure *caf)
320 ((StgIndStatic *)caf)->saved_info = (StgInfoTable *)caf->header.info;
321 ((StgIndStatic *)caf)->static_link = revertible_caf_list;
322 revertible_caf_list = caf;
327 /* -----------------------------------------------------------------------------
329 -------------------------------------------------------------------------- */
332 allocNursery (bdescr *tail, nat blocks)
337 // We allocate the nursery as a single contiguous block and then
338 // divide it into single blocks manually. This way we guarantee
339 // that the nursery blocks are adjacent, so that the processor's
340 // automatic prefetching works across nursery blocks. This is a
341 // tiny optimisation (~0.5%), but it's free.
344 n = stg_min(blocks, BLOCKS_PER_MBLOCK);
348 for (i = 0; i < n; i++) {
349 initBdescr(&bd[i], g0, g0);
355 bd[i].u.back = &bd[i-1];
361 bd[i].link = &bd[i+1];
365 tail->u.back = &bd[i];
369 bd[i].free = bd[i].start;
379 assignNurseriesToCapabilities (void)
383 for (i = 0; i < n_capabilities; i++) {
384 capabilities[i].r.rNursery = &nurseries[i];
385 capabilities[i].r.rCurrentNursery = nurseries[i].blocks;
386 capabilities[i].r.rCurrentAlloc = NULL;
391 allocNurseries( void )
395 for (i = 0; i < n_capabilities; i++) {
396 nurseries[i].blocks =
397 allocNursery(NULL, RtsFlags.GcFlags.minAllocAreaSize);
398 nurseries[i].n_blocks =
399 RtsFlags.GcFlags.minAllocAreaSize;
401 assignNurseriesToCapabilities();
404 lnat // words allocated
405 clearNurseries (void)
411 for (i = 0; i < n_capabilities; i++) {
412 for (bd = nurseries[i].blocks; bd; bd = bd->link) {
413 allocated += (lnat)(bd->free - bd->start);
414 bd->free = bd->start;
415 ASSERT(bd->gen_no == 0);
416 ASSERT(bd->gen == g0);
417 IF_DEBUG(sanity,memset(bd->start, 0xaa, BLOCK_SIZE));
425 resetNurseries (void)
427 assignNurseriesToCapabilities();
432 countNurseryBlocks (void)
437 for (i = 0; i < n_capabilities; i++) {
438 blocks += nurseries[i].n_blocks;
444 resizeNursery ( nursery *nursery, nat blocks )
449 nursery_blocks = nursery->n_blocks;
450 if (nursery_blocks == blocks) return;
452 if (nursery_blocks < blocks) {
453 debugTrace(DEBUG_gc, "increasing size of nursery to %d blocks",
455 nursery->blocks = allocNursery(nursery->blocks, blocks-nursery_blocks);
460 debugTrace(DEBUG_gc, "decreasing size of nursery to %d blocks",
463 bd = nursery->blocks;
464 while (nursery_blocks > blocks) {
466 next_bd->u.back = NULL;
467 nursery_blocks -= bd->blocks; // might be a large block
471 nursery->blocks = bd;
472 // might have gone just under, by freeing a large block, so make
473 // up the difference.
474 if (nursery_blocks < blocks) {
475 nursery->blocks = allocNursery(nursery->blocks, blocks-nursery_blocks);
479 nursery->n_blocks = blocks;
480 ASSERT(countBlocks(nursery->blocks) == nursery->n_blocks);
484 // Resize each of the nurseries to the specified size.
487 resizeNurseriesFixed (nat blocks)
490 for (i = 0; i < n_capabilities; i++) {
491 resizeNursery(&nurseries[i], blocks);
496 // Resize the nurseries to the total specified size.
499 resizeNurseries (nat blocks)
501 // If there are multiple nurseries, then we just divide the number
502 // of available blocks between them.
503 resizeNurseriesFixed(blocks / n_capabilities);
507 /* -----------------------------------------------------------------------------
508 move_STACK is called to update the TSO structure after it has been
509 moved from one place to another.
510 -------------------------------------------------------------------------- */
513 move_STACK (StgStack *src, StgStack *dest)
517 // relocate the stack pointer...
518 diff = (StgPtr)dest - (StgPtr)src; // In *words*
519 dest->sp = (StgPtr)dest->sp + diff;
522 /* -----------------------------------------------------------------------------
525 This allocates memory in the current thread - it is intended for
526 use primarily from STG-land where we have a Capability. It is
527 better than allocate() because it doesn't require taking the
528 sm_mutex lock in the common case.
530 Memory is allocated directly from the nursery if possible (but not
531 from the current nursery block, so as not to interfere with
533 -------------------------------------------------------------------------- */
536 allocate (Capability *cap, lnat n)
541 if (n >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
542 lnat req_blocks = (lnat)BLOCK_ROUND_UP(n*sizeof(W_)) / BLOCK_SIZE;
544 // Attempting to allocate an object larger than maxHeapSize
545 // should definitely be disallowed. (bug #1791)
546 if (RtsFlags.GcFlags.maxHeapSize > 0 &&
547 req_blocks >= RtsFlags.GcFlags.maxHeapSize) {
549 // heapOverflow() doesn't exit (see #2592), but we aren't
550 // in a position to do a clean shutdown here: we
551 // either have to allocate the memory or exit now.
552 // Allocating the memory would be bad, because the user
553 // has requested that we not exceed maxHeapSize, so we
555 stg_exit(EXIT_HEAPOVERFLOW);
559 bd = allocGroup(req_blocks);
560 dbl_link_onto(bd, &g0->large_objects);
561 g0->n_large_blocks += bd->blocks; // might be larger than req_blocks
562 g0->n_new_large_words += n;
564 initBdescr(bd, g0, g0);
565 bd->flags = BF_LARGE;
566 bd->free = bd->start + n;
570 /* small allocation (<LARGE_OBJECT_THRESHOLD) */
572 TICK_ALLOC_HEAP_NOCTR(n);
575 bd = cap->r.rCurrentAlloc;
576 if (bd == NULL || bd->free + n > bd->start + BLOCK_SIZE_W) {
578 // The CurrentAlloc block is full, we need to find another
579 // one. First, we try taking the next block from the
581 bd = cap->r.rCurrentNursery->link;
583 if (bd == NULL || bd->free + n > bd->start + BLOCK_SIZE_W) {
584 // The nursery is empty, or the next block is already
585 // full: allocate a fresh block (we can't fail here).
588 cap->r.rNursery->n_blocks++;
590 initBdescr(bd, g0, g0);
592 // If we had to allocate a new block, then we'll GC
593 // pretty quickly now, because MAYBE_GC() will
594 // notice that CurrentNursery->link is NULL.
596 // we have a block in the nursery: take it and put
597 // it at the *front* of the nursery list, and use it
598 // to allocate() from.
599 cap->r.rCurrentNursery->link = bd->link;
600 if (bd->link != NULL) {
601 bd->link->u.back = cap->r.rCurrentNursery;
604 dbl_link_onto(bd, &cap->r.rNursery->blocks);
605 cap->r.rCurrentAlloc = bd;
606 IF_DEBUG(sanity, checkNurserySanity(cap->r.rNursery));
611 IF_DEBUG(sanity, ASSERT(*((StgWord8*)p) == 0xaa));
615 /* ---------------------------------------------------------------------------
616 Allocate a fixed/pinned object.
618 We allocate small pinned objects into a single block, allocating a
619 new block when the current one overflows. The block is chained
620 onto the large_object_list of generation 0.
622 NOTE: The GC can't in general handle pinned objects. This
623 interface is only safe to use for ByteArrays, which have no
624 pointers and don't require scavenging. It works because the
625 block's descriptor has the BF_LARGE flag set, so the block is
626 treated as a large object and chained onto various lists, rather
627 than the individual objects being copied. However, when it comes
628 to scavenge the block, the GC will only scavenge the first object.
629 The reason is that the GC can't linearly scan a block of pinned
630 objects at the moment (doing so would require using the
631 mostly-copying techniques). But since we're restricting ourselves
632 to pinned ByteArrays, not scavenging is ok.
634 This function is called by newPinnedByteArray# which immediately
635 fills the allocated memory with a MutableByteArray#.
636 ------------------------------------------------------------------------- */
639 allocatePinned (Capability *cap, lnat n)
644 // If the request is for a large object, then allocate()
645 // will give us a pinned object anyway.
646 if (n >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
647 p = allocate(cap, n);
648 Bdescr(p)->flags |= BF_PINNED;
652 TICK_ALLOC_HEAP_NOCTR(n);
655 bd = cap->pinned_object_block;
657 // If we don't have a block of pinned objects yet, or the current
658 // one isn't large enough to hold the new object, allocate a new one.
659 if (bd == NULL || (bd->free + n) > (bd->start + BLOCK_SIZE_W)) {
661 cap->pinned_object_block = bd = allocBlock();
662 dbl_link_onto(bd, &g0->large_objects);
663 g0->n_large_blocks++;
665 initBdescr(bd, g0, g0);
666 bd->flags = BF_PINNED | BF_LARGE;
667 bd->free = bd->start;
670 g0->n_new_large_words += n;
676 /* -----------------------------------------------------------------------------
678 -------------------------------------------------------------------------- */
681 This is the write barrier for MUT_VARs, a.k.a. IORefs. A
682 MUT_VAR_CLEAN object is not on the mutable list; a MUT_VAR_DIRTY
683 is. When written to, a MUT_VAR_CLEAN turns into a MUT_VAR_DIRTY
684 and is put on the mutable list.
687 dirty_MUT_VAR(StgRegTable *reg, StgClosure *p)
689 Capability *cap = regTableToCapability(reg);
690 if (p->header.info == &stg_MUT_VAR_CLEAN_info) {
691 p->header.info = &stg_MUT_VAR_DIRTY_info;
692 recordClosureMutated(cap,p);
696 // Setting a TSO's link field with a write barrier.
697 // It is *not* necessary to call this function when
698 // * setting the link field to END_TSO_QUEUE
699 // * putting a TSO on the blackhole_queue
700 // * setting the link field of the currently running TSO, as it
701 // will already be dirty.
703 setTSOLink (Capability *cap, StgTSO *tso, StgTSO *target)
705 if (tso->dirty == 0) {
707 recordClosureMutated(cap,(StgClosure*)tso);
713 setTSOPrev (Capability *cap, StgTSO *tso, StgTSO *target)
715 if (tso->dirty == 0) {
717 recordClosureMutated(cap,(StgClosure*)tso);
719 tso->block_info.prev = target;
723 dirty_TSO (Capability *cap, StgTSO *tso)
725 if (tso->dirty == 0) {
727 recordClosureMutated(cap,(StgClosure*)tso);
732 dirty_STACK (Capability *cap, StgStack *stack)
734 if (stack->dirty == 0) {
736 recordClosureMutated(cap,(StgClosure*)stack);
741 This is the write barrier for MVARs. An MVAR_CLEAN objects is not
742 on the mutable list; a MVAR_DIRTY is. When written to, a
743 MVAR_CLEAN turns into a MVAR_DIRTY and is put on the mutable list.
744 The check for MVAR_CLEAN is inlined at the call site for speed,
745 this really does make a difference on concurrency-heavy benchmarks
746 such as Chaneneos and cheap-concurrency.
749 dirty_MVAR(StgRegTable *reg, StgClosure *p)
751 recordClosureMutated(regTableToCapability(reg),p);
754 /* -----------------------------------------------------------------------------
756 * -------------------------------------------------------------------------- */
758 /* -----------------------------------------------------------------------------
761 * Approximate how much we've allocated: number of blocks in the
762 * nursery + blocks allocated via allocate() - unused nusery blocks.
763 * This leaves a little slop at the end of each block.
764 * -------------------------------------------------------------------------- */
767 calcAllocated (rtsBool include_nurseries)
772 // When called from GC.c, we already have the allocation count for
773 // the nursery from resetNurseries(), so we don't need to walk
774 // through these block lists again.
775 if (include_nurseries)
777 for (i = 0; i < n_capabilities; i++) {
778 allocated += countOccupied(nurseries[i].blocks);
782 // add in sizes of new large and pinned objects
783 allocated += g0->n_new_large_words;
788 lnat countOccupied (bdescr *bd)
793 for (; bd != NULL; bd = bd->link) {
794 ASSERT(bd->free <= bd->start + bd->blocks * BLOCK_SIZE_W);
795 words += bd->free - bd->start;
800 lnat genLiveWords (generation *gen)
802 return gen->n_words + countOccupied(gen->large_objects);
805 lnat genLiveBlocks (generation *gen)
807 return gen->n_blocks + gen->n_large_blocks;
810 lnat gcThreadLiveWords (nat i, nat g)
814 words = countOccupied(gc_threads[i]->gens[g].todo_bd);
815 words += countOccupied(gc_threads[i]->gens[g].part_list);
816 words += countOccupied(gc_threads[i]->gens[g].scavd_list);
821 lnat gcThreadLiveBlocks (nat i, nat g)
825 blocks = countBlocks(gc_threads[i]->gens[g].todo_bd);
826 blocks += gc_threads[i]->gens[g].n_part_blocks;
827 blocks += gc_threads[i]->gens[g].n_scavd_blocks;
832 // Return an accurate count of the live data in the heap, excluding
834 lnat calcLiveWords (void)
840 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
841 live += genLiveWords(&generations[g]);
846 lnat calcLiveBlocks (void)
852 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
853 live += genLiveBlocks(&generations[g]);
858 /* Approximate the number of blocks that will be needed at the next
859 * garbage collection.
861 * Assume: all data currently live will remain live. Generationss
862 * that will be collected next time will therefore need twice as many
863 * blocks since all the data will be copied.
872 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
873 gen = &generations[g];
875 // we need at least this much space
876 needed += gen->n_blocks + gen->n_large_blocks;
878 // any additional space needed to collect this gen next time?
879 if (g == 0 || // always collect gen 0
880 (gen->n_blocks + gen->n_large_blocks > gen->max_blocks)) {
881 // we will collect this gen next time
884 needed += gen->n_blocks / BITS_IN(W_);
886 needed += gen->n_blocks / 100;
889 continue; // no additional space needed for compaction
891 needed += gen->n_blocks;
898 /* ----------------------------------------------------------------------------
901 Executable memory must be managed separately from non-executable
902 memory. Most OSs these days require you to jump through hoops to
903 dynamically allocate executable memory, due to various security
906 Here we provide a small memory allocator for executable memory.
907 Memory is managed with a page granularity; we allocate linearly
908 in the page, and when the page is emptied (all objects on the page
909 are free) we free the page again, not forgetting to make it
912 TODO: The inability to handle objects bigger than BLOCK_SIZE_W means that
913 the linker cannot use allocateExec for loading object code files
914 on Windows. Once allocateExec can handle larger objects, the linker
915 should be modified to use allocateExec instead of VirtualAlloc.
916 ------------------------------------------------------------------------- */
918 #if defined(linux_HOST_OS)
920 // On Linux we need to use libffi for allocating executable memory,
921 // because it knows how to work around the restrictions put in place
924 void *allocateExec (nat bytes, void **exec_ret)
928 ret = ffi_closure_alloc (sizeof(void *) + (size_t)bytes, (void**)&exec);
930 if (ret == NULL) return ret;
931 *ret = ret; // save the address of the writable mapping, for freeExec().
932 *exec_ret = exec + 1;
936 // freeExec gets passed the executable address, not the writable address.
937 void freeExec (void *addr)
940 writable = *((void**)addr - 1);
942 ffi_closure_free (writable);
948 void *allocateExec (nat bytes, void **exec_ret)
955 // round up to words.
956 n = (bytes + sizeof(W_) + 1) / sizeof(W_);
958 if (n+1 > BLOCK_SIZE_W) {
959 barf("allocateExec: can't handle large objects");
962 if (exec_block == NULL ||
963 exec_block->free + n + 1 > exec_block->start + BLOCK_SIZE_W) {
965 lnat pagesize = getPageSize();
966 bd = allocGroup(stg_max(1, pagesize / BLOCK_SIZE));
967 debugTrace(DEBUG_gc, "allocate exec block %p", bd->start);
970 bd->link = exec_block;
971 if (exec_block != NULL) {
972 exec_block->u.back = bd;
975 setExecutable(bd->start, bd->blocks * BLOCK_SIZE, rtsTrue);
978 *(exec_block->free) = n; // store the size of this chunk
979 exec_block->gen_no += n; // gen_no stores the number of words allocated
980 ret = exec_block->free + 1;
981 exec_block->free += n + 1;
988 void freeExec (void *addr)
990 StgPtr p = (StgPtr)addr - 1;
991 bdescr *bd = Bdescr((StgPtr)p);
993 if ((bd->flags & BF_EXEC) == 0) {
994 barf("freeExec: not executable");
997 if (*(StgPtr)p == 0) {
998 barf("freeExec: already free?");
1003 bd->gen_no -= *(StgPtr)p;
1006 if (bd->gen_no == 0) {
1007 // Free the block if it is empty, but not if it is the block at
1008 // the head of the queue.
1009 if (bd != exec_block) {
1010 debugTrace(DEBUG_gc, "free exec block %p", bd->start);
1011 dbl_link_remove(bd, &exec_block);
1012 setExecutable(bd->start, bd->blocks * BLOCK_SIZE, rtsFalse);
1015 bd->free = bd->start;
1022 #endif /* mingw32_HOST_OS */
1026 // handy function for use in gdb, because Bdescr() is inlined.
1027 extern bdescr *_bdescr( StgPtr p );