#include "MBlock.h"
#include "Evac.h"
#include "GC.h"
+#include "GCThread.h"
#include "GCUtils.h"
#include "Compact.h"
#include "Prelude.h"
#include "LdvProfile.h"
+#if defined(PROF_SPIN) && defined(THREADED_RTS)
+StgWord64 whitehole_spin = 0;
+#endif
+
/* Used to avoid long recursion due to selector thunks
*/
#define MAX_THUNK_SELECTOR_DEPTH 16
-static StgClosure * eval_thunk_selector (StgSelector * p, rtsBool);
+static void eval_thunk_selector (StgClosure **q, StgSelector * p, rtsBool);
+STATIC_INLINE void evacuate_large(StgPtr p);
+
+/* -----------------------------------------------------------------------------
+ Allocate some space in which to copy an object.
+ -------------------------------------------------------------------------- */
STATIC_INLINE StgPtr
alloc_for_copy (nat size, step *stp)
{
StgPtr to;
step_workspace *ws;
- bdescr *bd;
/* Find out where we're going, using the handy "to" pointer in
* the step of the source object. If it turns out we need to
* evacuate to an older generation, adjust it here (see comment
* by evacuate()).
*/
- if (stp->gen_no < gct->evac_gen) {
+ if (stp < gct->evac_step) {
if (gct->eager_promotion) {
- stp = &generations[gct->evac_gen].steps[0];
+ stp = gct->evac_step;
} else {
gct->failed_to_evac = rtsTrue;
}
}
- ws = &gct->steps[stp->gen_no][stp->no];
+ ws = &gct->steps[stp->abs_no];
+ // this compiles to a single mem access to stp->abs_no only
/* chain a new block onto the to-space for the destination step if
* necessary.
*/
- bd = ws->todo_bd;
- to = bd->free;
- if (to + size >= bd->start + BLOCK_SIZE_W) {
- bd = gc_alloc_todo_block(ws);
- to = bd->free;
+ to = ws->todo_free;
+ if (to + size > ws->todo_lim) {
+ to = todo_block_full(size, ws);
}
- bd->free = to + size;
+ ws->todo_free = to + size;
+ ASSERT(ws->todo_free >= ws->todo_bd->free && ws->todo_free <= ws->todo_lim);
return to;
}
-
-STATIC_INLINE StgPtr
-alloc_for_copy_noscav (nat size, step *stp)
-{
- StgPtr to;
- step_workspace *ws;
- bdescr *bd;
-
- /* Find out where we're going, using the handy "to" pointer in
- * the step of the source object. If it turns out we need to
- * evacuate to an older generation, adjust it here (see comment
- * by evacuate()).
- */
- if (stp->gen_no < gct->evac_gen) {
- if (gct->eager_promotion) {
- stp = &generations[gct->evac_gen].steps[0];
- } else {
- gct->failed_to_evac = rtsTrue;
- }
- }
-
- ws = &gct->steps[stp->gen_no][stp->no];
-
- /* chain a new block onto the to-space for the destination step if
- * necessary.
- */
- bd = ws->scavd_list;
- to = bd->free;
- if (to + size >= bd->start + BLOCK_SIZE_W) {
- bd = gc_alloc_scavd_block(ws);
- to = bd->free;
- }
- bd->free = to + size;
-
- return to;
-}
-
-STATIC_INLINE StgClosure *
-copy_tag(StgClosure *src, nat size, step *stp,StgWord tag)
-{
- StgPtr to, from;
- nat i;
- StgWord info;
-
-#ifdef THREADED_RTS
- do {
- info = xchg((StgPtr)&src->header.info, (W_)&stg_WHITEHOLE_info);
- // so.. what is it?
- } while (info == (W_)&stg_WHITEHOLE_info);
- if (info == (W_)&stg_EVACUATED_info) {
- src->header.info = (const StgInfoTable *)info;
- return evacuate(src); // does the failed_to_evac stuff
- }
-#else
- info = (W_)src->header.info;
- src->header.info = &stg_EVACUATED_info;
-#endif
-
- to = alloc_for_copy(size,stp);
-
- TICK_GC_WORDS_COPIED(size);
-
- from = (StgPtr)src;
- to[0] = info;
- for (i = 1; i < size; i++) { // unroll for small i
- to[i] = from[i];
- }
-
- // retag pointer before updating EVACUATE closure and returning
- to = (StgPtr)TAG_CLOSURE(tag,(StgClosure*)to);
-
-// if (to+size+2 < bd->start + BLOCK_SIZE_W) {
-// __builtin_prefetch(to + size + 2, 1);
-// }
-
- ((StgEvacuated*)from)->evacuee = (StgClosure *)to;
-#ifdef THREADED_RTS
- write_barrier();
- ((StgEvacuated*)from)->header.info = &stg_EVACUATED_info;
-#endif
-
-#ifdef PROFILING
- // We store the size of the just evacuated object in the LDV word so that
- // the profiler can guess the position of the next object later.
- SET_EVACUAEE_FOR_LDV(from, size);
-#endif
- return (StgClosure *)to;
-}
-
-
-// Same as copy() above, except the object will be allocated in memory
-// that will not be scavenged. Used for object that have no pointer
-// fields.
-STATIC_INLINE StgClosure *
-copy_noscav_tag(StgClosure *src, nat size, step *stp, StgWord tag)
-{
- StgPtr to, from;
- nat i;
- StgWord info;
-
-#ifdef THREADED_RTS
- do {
- info = xchg((StgPtr)&src->header.info, (W_)&stg_WHITEHOLE_info);
- } while (info == (W_)&stg_WHITEHOLE_info);
- if (info == (W_)&stg_EVACUATED_info) {
- src->header.info = (const StgInfoTable *)info;
- return evacuate(src); // does the failed_to_evac stuff
- }
-#else
- info = (W_)src->header.info;
- src->header.info = &stg_EVACUATED_info;
-#endif
-
- to = alloc_for_copy_noscav(size,stp);
-
- TICK_GC_WORDS_COPIED(size);
-
- from = (StgPtr)src;
- to[0] = info;
- for (i = 1; i < size; i++) { // unroll for small i
- to[i] = from[i];
- }
-
- // retag pointer before updating EVACUATE closure and returning
- to = (StgPtr)TAG_CLOSURE(tag,(StgClosure*)to);
-
- ((StgEvacuated*)from)->evacuee = (StgClosure *)to;
-#ifdef THREADED_RTS
- write_barrier();
- ((StgEvacuated*)from)->header.info = &stg_EVACUATED_info;
-#endif
-
-#ifdef PROFILING
- // We store the size of the just evacuated object in the LDV word so that
- // the profiler can guess the position of the next object later.
- SET_EVACUAEE_FOR_LDV(from, size);
-#endif
- return (StgClosure *)to;
-}
-
-
-/* Special version of copy() for when we only want to copy the info
- * pointer of an object, but reserve some padding after it. This is
- * used to optimise evacuation of BLACKHOLEs.
- */
-static StgClosure *
-copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
-{
- StgPtr to, from;
- nat i;
- StgWord info;
-
-#ifdef THREADED_RTS
- do {
- info = xchg((StgPtr)&src->header.info, (W_)&stg_WHITEHOLE_info);
- } while (info == (W_)&stg_WHITEHOLE_info);
- if (info == (W_)&stg_EVACUATED_info) {
- src->header.info = (const StgInfoTable *)info;
- return evacuate(src); // does the failed_to_evac stuff
- }
-#else
- info = (W_)src->header.info;
- src->header.info = &stg_EVACUATED_info;
-#endif
-
- to = alloc_for_copy(size_to_reserve, stp);
-
- TICK_GC_WORDS_COPIED(size_to_copy);
-
- from = (StgPtr)src;
- to[0] = info;
- for (i = 1; i < size_to_copy; i++) { // unroll for small i
- to[i] = from[i];
- }
-
- ((StgEvacuated*)from)->evacuee = (StgClosure *)to;
-#ifdef THREADED_RTS
- write_barrier();
- ((StgEvacuated*)from)->header.info = &stg_EVACUATED_info;
-#endif
-
-#ifdef PROFILING
- // We store the size of the just evacuated object in the LDV word so that
- // the profiler can guess the position of the next object later.
- SET_EVACUAEE_FOR_LDV(from, size_to_reserve);
- // fill the slop
- if (size_to_reserve - size_to_copy > 0)
- LDV_FILL_SLOP(to + size_to_copy - 1, (int)(size_to_reserve - size_to_copy));
-#endif
- return (StgClosure *)to;
-}
+/* -----------------------------------------------------------------------------
+ The evacuate() code
+ -------------------------------------------------------------------------- */
-/* Copy wrappers that don't tag the closure after copying */
-STATIC_INLINE StgClosure *
-copy(StgClosure *src, nat size, step *stp)
-{
- return copy_tag(src,size,stp,0);
-}
+#define PARALLEL_GC
+#include "Evac.c-inc"
-STATIC_INLINE StgClosure *
-copy_noscav(StgClosure *src, nat size, step *stp)
-{
- return copy_noscav_tag(src,size,stp,0);
-}
+#undef PARALLEL_GC
+#include "Evac.c-inc"
/* -----------------------------------------------------------------------------
Evacuate a large object
that has been evacuated, or unset otherwise.
-------------------------------------------------------------------------- */
-
STATIC_INLINE void
evacuate_large(StgPtr p)
{
bdescr *bd = Bdescr(p);
- step *stp;
+ step *stp, *new_stp;
step_workspace *ws;
+
+ stp = bd->step;
+ ACQUIRE_SPIN_LOCK(&stp->sync_large_objects);
// object must be at the beginning of the block (or be a ByteArray)
ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
/* Don't forget to set the gct->failed_to_evac flag if we didn't get
* the desired destination (see comments in evacuate()).
*/
- if (bd->gen_no < gct->evac_gen) {
- gct->failed_to_evac = rtsTrue;
- TICK_GC_FAILED_PROMOTION();
+ if (stp < gct->evac_step) {
+ gct->failed_to_evac = rtsTrue;
+ TICK_GC_FAILED_PROMOTION();
}
+ RELEASE_SPIN_LOCK(&stp->sync_large_objects);
return;
}
- stp = bd->step;
-
- ACQUIRE_SPIN_LOCK(&stp->sync_large_objects);
// remove from large_object list
if (bd->u.back) {
bd->u.back->link = bd->link;
if (bd->link) {
bd->link->u.back = bd->u.back;
}
- RELEASE_SPIN_LOCK(&stp->sync_large_objects);
/* link it on to the evacuated large object list of the destination step
*/
- stp = bd->step->to;
- if (stp->gen_no < gct->evac_gen) {
+ new_stp = stp->to;
+ if (new_stp < gct->evac_step) {
if (gct->eager_promotion) {
- stp = &generations[gct->evac_gen].steps[0];
+ new_stp = gct->evac_step;
} else {
gct->failed_to_evac = rtsTrue;
}
}
- ws = &gct->steps[stp->gen_no][stp->no];
- bd->step = stp;
- bd->gen_no = stp->gen_no;
+ ws = &gct->steps[new_stp->abs_no];
+ bd->flags |= BF_EVACUATED;
+ bd->step = new_stp;
+ bd->gen_no = new_stp->gen_no;
bd->link = ws->todo_large_objects;
ws->todo_large_objects = bd;
- bd->flags |= BF_EVACUATED;
+
+ RELEASE_SPIN_LOCK(&stp->sync_large_objects);
}
/* -----------------------------------------------------------------------------
- Evacuate
-
- This is called (eventually) for every live object in the system.
-
- The caller to evacuate specifies a desired generation in the
- gct->evac_gen thread-lock variable. The following conditions apply to
- evacuating an object which resides in generation M when we're
- collecting up to generation N
-
- if M >= gct->evac_gen
- if M > N do nothing
- else evac to step->to
-
- if M < gct->evac_gen evac to gct->evac_gen, step 0
-
- if the object is already evacuated, then we check which generation
- it now resides in.
-
- if M >= gct->evac_gen do nothing
- if M < gct->evac_gen set gct->failed_to_evac flag to indicate that we
- didn't manage to evacuate this object into gct->evac_gen.
-
-
- OPTIMISATION NOTES:
+ Evaluate a THUNK_SELECTOR if possible.
- evacuate() is the single most important function performance-wise
- in the GC. Various things have been tried to speed it up, but as
- far as I can tell the code generated by gcc 3.2 with -O2 is about
- as good as it's going to get. We pass the argument to evacuate()
- in a register using the 'regparm' attribute (see the prototype for
- evacuate() near the top of this file).
+ p points to a THUNK_SELECTOR that we want to evaluate. The
+ result of "evaluating" it will be evacuated and a pointer to the
+ to-space closure will be returned.
- Changing evacuate() to take an (StgClosure **) rather than
- returning the new pointer seems attractive, because we can avoid
- writing back the pointer when it hasn't changed (eg. for a static
- object, or an object in a generation > N). However, I tried it and
- it doesn't help. One reason is that the (StgClosure **) pointer
- gets spilled to the stack inside evacuate(), resulting in far more
- extra reads/writes than we save.
+ If the THUNK_SELECTOR could not be evaluated (its selectee is still
+ a THUNK, for example), then the THUNK_SELECTOR itself will be
+ evacuated.
-------------------------------------------------------------------------- */
-
-REGPARM1 StgClosure *
-evacuate(StgClosure *q)
-{
- bdescr *bd = NULL;
- step *stp;
- const StgInfoTable *info;
- StgWord tag;
-
-loop:
- /* The tag and the pointer are split, to be merged after evacing */
- tag = GET_CLOSURE_TAG(q);
- q = UNTAG_CLOSURE(q);
-
- ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
-
- if (!HEAP_ALLOCED(q)) {
-
- if (!major_gc) return TAG_CLOSURE(tag,q);
-
- info = get_itbl(q);
- switch (info->type) {
-
- case THUNK_STATIC:
- if (info->srt_bitmap != 0 &&
- *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
- ACQUIRE_SPIN_LOCK(&static_objects_sync);
- if (*THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
- *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
- static_objects = (StgClosure *)q;
- }
- RELEASE_SPIN_LOCK(&static_objects_sync);
- }
- return q;
-
- case FUN_STATIC:
- if (info->srt_bitmap != 0 &&
- *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
- ACQUIRE_SPIN_LOCK(&static_objects_sync);
- if (*FUN_STATIC_LINK((StgClosure *)q) == NULL) {
- *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
- static_objects = (StgClosure *)q;
- }
- RELEASE_SPIN_LOCK(&static_objects_sync);
- }
- return q;
-
- case IND_STATIC:
- /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
- * on the CAF list, so don't do anything with it here (we'll
- * scavenge it later).
- */
- if (((StgIndStatic *)q)->saved_info == NULL) {
- ACQUIRE_SPIN_LOCK(&static_objects_sync);
- if (*IND_STATIC_LINK((StgClosure *)q) == NULL) {
- *IND_STATIC_LINK((StgClosure *)q) = static_objects;
- static_objects = (StgClosure *)q;
- }
- RELEASE_SPIN_LOCK(&static_objects_sync);
- }
- return q;
-
- case CONSTR_STATIC:
- if (*STATIC_LINK(info,(StgClosure *)q) == NULL) {
- ACQUIRE_SPIN_LOCK(&static_objects_sync);
- // re-test, after acquiring lock
- if (*STATIC_LINK(info,(StgClosure *)q) == NULL) {
- *STATIC_LINK(info,(StgClosure *)q) = static_objects;
- static_objects = (StgClosure *)q;
- }
- RELEASE_SPIN_LOCK(&static_objects_sync);
- /* I am assuming that static_objects pointers are not
- * written to other objects, and thus, no need to retag. */
- }
- return TAG_CLOSURE(tag,q);
-
- case CONSTR_NOCAF_STATIC:
- /* no need to put these on the static linked list, they don't need
- * to be scavenged.
- */
- return TAG_CLOSURE(tag,q);
-
- default:
- barf("evacuate(static): strange closure type %d", (int)(info->type));
- }
- }
-
- bd = Bdescr((P_)q);
-
- if (bd->gen_no > N) {
- /* Can't evacuate this object, because it's in a generation
- * older than the ones we're collecting. Let's hope that it's
- * in gct->evac_gen or older, or we will have to arrange to track
- * this pointer using the mutable list.
- */
- if (bd->gen_no < gct->evac_gen) {
- // nope
- gct->failed_to_evac = rtsTrue;
- TICK_GC_FAILED_PROMOTION();
- }
- return TAG_CLOSURE(tag,q);
- }
-
- if ((bd->flags & (BF_LARGE | BF_COMPACTED | BF_EVACUATED)) != 0) {
-
- /* pointer into to-space: just return it. This normally
- * shouldn't happen, but alllowing it makes certain things
- * slightly easier (eg. the mutable list can contain the same
- * object twice, for example).
- */
- if (bd->flags & BF_EVACUATED) {
- if (bd->gen_no < gct->evac_gen) {
- gct->failed_to_evac = rtsTrue;
- TICK_GC_FAILED_PROMOTION();
- }
- return TAG_CLOSURE(tag,q);
- }
-
- /* evacuate large objects by re-linking them onto a different list.
- */
- if (bd->flags & BF_LARGE) {
- info = get_itbl(q);
- if (info->type == TSO &&
- ((StgTSO *)q)->what_next == ThreadRelocated) {
- q = (StgClosure *)((StgTSO *)q)->link;
- goto loop;
- }
- evacuate_large((P_)q);
- return TAG_CLOSURE(tag,q);
- }
-
- /* If the object is in a step that we're compacting, then we
- * need to use an alternative evacuate procedure.
- */
- if (bd->flags & BF_COMPACTED) {
- if (!is_marked((P_)q,bd)) {
- mark((P_)q,bd);
- if (mark_stack_full()) {
- mark_stack_overflowed = rtsTrue;
- reset_mark_stack();
- }
- push_mark_stack((P_)q);
- }
- return TAG_CLOSURE(tag,q);
- }
- }
-
- stp = bd->step->to;
-
- info = get_itbl(q);
-
- switch (info->type) {
-
- case WHITEHOLE:
- goto loop;
-
- case MUT_VAR_CLEAN:
- case MUT_VAR_DIRTY:
- case MVAR_CLEAN:
- case MVAR_DIRTY:
- return copy(q,sizeW_fromITBL(info),stp);
-
- case CONSTR_0_1:
- {
- StgWord w = (StgWord)q->payload[0];
- if (q->header.info == Czh_con_info &&
- // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
- (StgChar)w <= MAX_CHARLIKE) {
- return TAG_CLOSURE(tag,
- (StgClosure *)CHARLIKE_CLOSURE((StgChar)w)
- );
- }
- if (q->header.info == Izh_con_info &&
- (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
- return TAG_CLOSURE(tag,
- (StgClosure *)INTLIKE_CLOSURE((StgInt)w)
- );
- }
- // else
- return copy_noscav_tag(q,sizeofW(StgHeader)+1,stp,tag);
- }
-
- case FUN_0_1:
- case FUN_1_0:
- case CONSTR_1_0:
- return copy_tag(q,sizeofW(StgHeader)+1,stp,tag);
-
- case THUNK_1_0:
- case THUNK_0_1:
- return copy(q,sizeofW(StgThunk)+1,stp);
-
- case THUNK_1_1:
- case THUNK_2_0:
- case THUNK_0_2:
-#ifdef NO_PROMOTE_THUNKS
- if (bd->gen_no == 0 &&
- bd->step->no != 0 &&
- bd->step->no == generations[bd->gen_no].n_steps-1) {
- stp = bd->step;
- }
-#endif
- return copy(q,sizeofW(StgThunk)+2,stp);
-
- case FUN_1_1:
- case FUN_2_0:
- case FUN_0_2:
- case CONSTR_1_1:
- case CONSTR_2_0:
- return copy_tag(q,sizeofW(StgHeader)+2,stp,tag);
-
- case CONSTR_0_2:
- return copy_noscav_tag(q,sizeofW(StgHeader)+2,stp,tag);
-
- case THUNK:
- return copy(q,thunk_sizeW_fromITBL(info),stp);
-
- case FUN:
- case IND_PERM:
- case IND_OLDGEN_PERM:
- case WEAK:
- case STABLE_NAME:
- case CONSTR:
- return copy_tag(q,sizeW_fromITBL(info),stp,tag);
-
- case BCO:
- return copy(q,bco_sizeW((StgBCO *)q),stp);
-
- case CAF_BLACKHOLE:
- case SE_CAF_BLACKHOLE:
- case SE_BLACKHOLE:
- case BLACKHOLE:
- return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
-
- case THUNK_SELECTOR:
- return eval_thunk_selector((StgSelector *)q, rtsTrue);
-
- case IND:
- case IND_OLDGEN:
- // follow chains of indirections, don't evacuate them
- q = ((StgInd*)q)->indirectee;
- goto loop;
-
- case RET_BCO:
- case RET_SMALL:
- case RET_BIG:
- case RET_DYN:
- case UPDATE_FRAME:
- case STOP_FRAME:
- case CATCH_FRAME:
- case CATCH_STM_FRAME:
- case CATCH_RETRY_FRAME:
- case ATOMICALLY_FRAME:
- // shouldn't see these
- barf("evacuate: stack frame at %p\n", q);
-
- case PAP:
- return copy(q,pap_sizeW((StgPAP*)q),stp);
-
- case AP:
- return copy(q,ap_sizeW((StgAP*)q),stp);
-
- case AP_STACK:
- return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
-
- case EVACUATED:
- /* Already evacuated, just return the forwarding address.
- * HOWEVER: if the requested destination generation (gct->evac_gen) is
- * older than the actual generation (because the object was
- * already evacuated to a younger generation) then we have to
- * set the gct->failed_to_evac flag to indicate that we couldn't
- * manage to promote the object to the desired generation.
- */
- /*
- * Optimisation: the check is fairly expensive, but we can often
- * shortcut it if either the required generation is 0, or the
- * current object (the EVACUATED) is in a high enough generation.
- * We know that an EVACUATED always points to an object in the
- * same or an older generation. stp is the lowest step that the
- * current object would be evacuated to, so we only do the full
- * check if stp is too low.
- */
- if (gct->evac_gen > 0 && stp->gen_no < gct->evac_gen) { // optimisation
- StgClosure *p = ((StgEvacuated*)q)->evacuee;
- if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < gct->evac_gen) {
- gct->failed_to_evac = rtsTrue;
- TICK_GC_FAILED_PROMOTION();
- }
- }
- return ((StgEvacuated*)q)->evacuee;
-
- case ARR_WORDS:
- // just copy the block
- return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp);
-
- case MUT_ARR_PTRS_CLEAN:
- case MUT_ARR_PTRS_DIRTY:
- case MUT_ARR_PTRS_FROZEN:
- case MUT_ARR_PTRS_FROZEN0:
- // just copy the block
- return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
-
- case TSO:
- {
- StgTSO *tso = (StgTSO *)q;
-
- /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
- */
- if (tso->what_next == ThreadRelocated) {
- q = (StgClosure *)tso->link;
- goto loop;
- }
-
- /* To evacuate a small TSO, we need to relocate the update frame
- * list it contains.
- */
- {
- StgTSO *new_tso;
- StgPtr p, q;
-
- new_tso = (StgTSO *)copyPart((StgClosure *)tso,
- tso_sizeW(tso),
- sizeofW(StgTSO), stp);
- move_TSO(tso, new_tso);
- for (p = tso->sp, q = new_tso->sp;
- p < tso->stack+tso->stack_size;) {
- *q++ = *p++;
- }
-
- return (StgClosure *)new_tso;
- }
- }
-
- case TREC_HEADER:
- return copy(q,sizeofW(StgTRecHeader),stp);
-
- case TVAR_WATCH_QUEUE:
- return copy(q,sizeofW(StgTVarWatchQueue),stp);
-
- case TVAR:
- return copy(q,sizeofW(StgTVar),stp);
-
- case TREC_CHUNK:
- return copy(q,sizeofW(StgTRecChunk),stp);
-
- case ATOMIC_INVARIANT:
- return copy(q,sizeofW(StgAtomicInvariant),stp);
-
- case INVARIANT_CHECK_QUEUE:
- return copy(q,sizeofW(StgInvariantCheckQueue),stp);
-
- default:
- barf("evacuate: strange closure type %d", (int)(info->type));
- }
-
- barf("evacuate");
-}
-
static void
unchain_thunk_selectors(StgSelector *p, StgClosure *val)
{
prev = NULL;
while (p)
{
+#ifdef THREADED_RTS
+ ASSERT(p->header.info == &stg_WHITEHOLE_info);
+#else
ASSERT(p->header.info == &stg_BLACKHOLE_info);
+#endif
+ // val must be in to-space. Not always: when we recursively
+ // invoke eval_thunk_selector(), the recursive calls will not
+ // evacuate the value (because we want to select on the value,
+ // not evacuate it), so in this case val is in from-space.
+ // ASSERT(!HEAP_ALLOCED(val) || Bdescr((P_)val)->gen_no > N || (Bdescr((P_)val)->flags & BF_EVACUATED));
+
prev = (StgSelector*)((StgClosure *)p)->payload[0];
// Update the THUNK_SELECTOR with an indirection to the
// EVACUATED closure always points to an object in the
// same or an older generation (required by the short-cut
// test in the EVACUATED case, below).
- SET_INFO(p, &stg_IND_info);
((StgInd *)p)->indirectee = val;
+ write_barrier();
+ SET_INFO(p, &stg_IND_info);
// For the purposes of LDV profiling, we have created an
// indirection.
}
}
-/* -----------------------------------------------------------------------------
- Evaluate a THUNK_SELECTOR if possible.
-
- p points to a THUNK_SELECTOR that we want to evaluate. The
- result of "evaluating" it will be evacuated and a pointer to the
- to-space closure will be returned.
-
- If the THUNK_SELECTOR could not be evaluated (its selectee is still
- a THUNK, for example), then the THUNK_SELECTOR itself will be
- evacuated.
- -------------------------------------------------------------------------- */
-
-static StgClosure *
-eval_thunk_selector (StgSelector * p, rtsBool evac)
+static void
+eval_thunk_selector (StgClosure **q, StgSelector * p, rtsBool evac)
+ // NB. for legacy reasons, p & q are swapped around :(
{
nat field;
StgInfoTable *info;
- const StgInfoTable *info_ptr;
+ StgWord info_ptr;
StgClosure *selectee;
StgSelector *prev_thunk_selector;
bdescr *bd;
selector_chain:
- // The selectee might be a constructor closure,
- // so we untag the pointer.
- selectee = UNTAG_CLOSURE(p->selectee);
-
- // Save the real info pointer (NOTE: not the same as get_itbl()).
- info_ptr = p->header.info;
- field = get_itbl(p)->layout.selector_offset;
-
bd = Bdescr((StgPtr)p);
if (HEAP_ALLOCED(p)) {
// If the THUNK_SELECTOR is in to-space or in a generation that we
// mutable list.
if ((bd->gen_no > N) || (bd->flags & BF_EVACUATED)) {
unchain_thunk_selectors(prev_thunk_selector, (StgClosure *)p);
- return (StgClosure *)p;
+ *q = (StgClosure *)p;
+ return;
}
// we don't update THUNK_SELECTORS in the compacted
// generation, because compaction does not remove the INDs
// around here, test by compiling stage 3 with +RTS -c -RTS.
if (bd->flags & BF_COMPACTED) {
// must call evacuate() to mark this closure if evac==rtsTrue
- if (evac) p = (StgSelector *)evacuate((StgClosure *)p);
+ *q = (StgClosure *)p;
+ if (evac) evacuate(q);
unchain_thunk_selectors(prev_thunk_selector, (StgClosure *)p);
- return (StgClosure *)p;
+ return;
}
}
+
// BLACKHOLE the selector thunk, since it is now under evaluation.
// This is important to stop us going into an infinite loop if
// this selector thunk eventually refers to itself.
+#if defined(THREADED_RTS)
+ // In threaded mode, we'll use WHITEHOLE to lock the selector
+ // thunk while we evaluate it.
+ {
+ do {
+ info_ptr = xchg((StgPtr)&p->header.info, (W_)&stg_WHITEHOLE_info);
+ } while (info_ptr == (W_)&stg_WHITEHOLE_info);
+
+ // make sure someone else didn't get here first...
+ if (INFO_PTR_TO_STRUCT(info_ptr)->type != THUNK_SELECTOR) {
+ // v. tricky now. The THUNK_SELECTOR has been evacuated
+ // by another thread, and is now either EVACUATED or IND.
+ // We need to extract ourselves from the current situation
+ // as cleanly as possible.
+ // - unlock the closure
+ // - update *q, we may have done *some* evaluation
+ // - if evac, we need to call evacuate(), because we
+ // need the write-barrier stuff.
+ // - undo the chain we've built to point to p.
+ SET_INFO(p, (const StgInfoTable *)info_ptr);
+ *q = (StgClosure *)p;
+ if (evac) evacuate(q);
+ unchain_thunk_selectors(prev_thunk_selector, (StgClosure *)p);
+ return;
+ }
+ }
+#else
+ // Save the real info pointer (NOTE: not the same as get_itbl()).
+ info_ptr = (StgWord)p->header.info;
SET_INFO(p,&stg_BLACKHOLE_info);
+#endif
+
+ field = INFO_PTR_TO_STRUCT(info_ptr)->layout.selector_offset;
+
+ // The selectee might be a constructor closure,
+ // so we untag the pointer.
+ selectee = UNTAG_CLOSURE(p->selectee);
selector_loop:
// selectee now points to the closure that we're trying to select
info = get_itbl(selectee);
switch (info->type) {
+ case WHITEHOLE:
+ goto bale_out; // about to be evacuated by another thread (or a loop).
+
case CONSTR:
case CONSTR_1_0:
case CONSTR_0_1:
#ifdef PROFILING
// For the purposes of LDV profiling, we have destroyed
// the original selector thunk, p.
- SET_INFO(p, info_ptr);
+ SET_INFO(p, (StgInfoTable *)info_ptr);
LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC((StgClosure *)p);
SET_INFO(p, &stg_BLACKHOLE_info);
#endif
((StgClosure*)p)->payload[0] = (StgClosure *)prev_thunk_selector;
prev_thunk_selector = p;
- if (evac) val = evacuate(val);
+ *q = val;
+ if (evac) evacuate(q);
+ val = *q;
// evacuate() cannot recurse through
// eval_thunk_selector(), because we know val is not
// a THUNK_SELECTOR.
unchain_thunk_selectors(prev_thunk_selector, val);
- return val;
+ return;
}
}
// rtsFalse says "don't evacuate the result". It will,
// however, update any THUNK_SELECTORs that are evaluated
// along the way.
- val = eval_thunk_selector((StgSelector *)selectee, rtsFalse);
+ eval_thunk_selector(&val, (StgSelector*)selectee, rtsFalse);
gct->thunk_selector_depth--;
// did we actually manage to evaluate it?
bale_out:
// We didn't manage to evaluate this thunk; restore the old info
// pointer. But don't forget: we still need to evacuate the thunk itself.
- SET_INFO(p, info_ptr);
+ SET_INFO(p, (const StgInfoTable *)info_ptr);
+ // THREADED_RTS: we just unlocked the thunk, so another thread
+ // might get in and update it. copy() will lock it again and
+ // check whether it was updated in the meantime.
+ *q = (StgClosure *)p;
if (evac) {
- val = copy((StgClosure *)p,THUNK_SELECTOR_sizeW(),bd->step->to);
- } else {
- val = (StgClosure *)p;
+ copy(q,(StgClosure *)p,THUNK_SELECTOR_sizeW(),bd->step->to);
}
- unchain_thunk_selectors(prev_thunk_selector, val);
- return val;
+ unchain_thunk_selectors(prev_thunk_selector, *q);
+ return;
}
/* -----------------------------------------------------------------------------
projects / ghc-hetmet.git / blobdiff