/* * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers * Copyright (c) 1991-1995 by Xerox Corporation. All rights reserved. * Copyright (c) 2000 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. * */ # include # include "private/gc_pmark.h" #if defined(MSWIN32) && defined(__GNUC__) # include #endif /* We put this here to minimize the risk of inlining. */ /*VARARGS*/ #if defined(__BORLANDC__) || defined(__WATCOMC__) /*ARGSUSED*/ void GC_noop(void *p, ...) {} #else # ifdef __DMC__ void GC_noop(...) {} # else void GC_noop() {} # endif #endif /* Single argument version, robust against whole program analysis. */ GC_API void GC_CALL GC_noop1(word x) { static volatile word sink; sink = x; } /* mark_proc GC_mark_procs[MAX_MARK_PROCS] = {0} -- declared in gc_priv.h */ unsigned GC_n_mark_procs = GC_RESERVED_MARK_PROCS; /* Initialize GC_obj_kinds properly and standard free lists properly. */ /* This must be done statically since they may be accessed before */ /* GC_init is called. */ /* It's done here, since we need to deal with mark descriptors. */ struct obj_kind GC_obj_kinds[MAXOBJKINDS] = { /* PTRFREE */ { &GC_aobjfreelist[0], 0 /* filled in dynamically */, 0 | GC_DS_LENGTH, FALSE, FALSE }, /* NORMAL */ { &GC_objfreelist[0], 0, 0 | GC_DS_LENGTH, /* Adjusted in GC_init_inner for EXTRA_BYTES */ TRUE /* add length to descr */, TRUE }, /* UNCOLLECTABLE */ { &GC_uobjfreelist[0], 0, 0 | GC_DS_LENGTH, TRUE /* add length to descr */, TRUE }, # ifdef ATOMIC_UNCOLLECTABLE /* AUNCOLLECTABLE */ { &GC_auobjfreelist[0], 0, 0 | GC_DS_LENGTH, FALSE /* add length to descr */, FALSE }, # endif # ifdef STUBBORN_ALLOC /*STUBBORN*/ { (void **)&GC_sobjfreelist[0], 0, 0 | GC_DS_LENGTH, TRUE /* add length to descr */, TRUE }, # endif }; # ifdef ATOMIC_UNCOLLECTABLE # ifdef STUBBORN_ALLOC unsigned GC_n_kinds = 5; # else unsigned GC_n_kinds = 4; # endif # else # ifdef STUBBORN_ALLOC unsigned GC_n_kinds = 4; # else unsigned GC_n_kinds = 3; # endif # endif # ifndef INITIAL_MARK_STACK_SIZE # define INITIAL_MARK_STACK_SIZE (1*HBLKSIZE) /* INITIAL_MARK_STACK_SIZE * sizeof(mse) should be a */ /* multiple of HBLKSIZE. */ /* The incremental collector actually likes a larger */ /* size, since it want to push all marked dirty objs */ /* before marking anything new. Currently we let it */ /* grow dynamically. */ # endif /* * Limits of stack for GC_mark routine. * All ranges between GC_mark_stack(incl.) and GC_mark_stack_top(incl.) still * need to be marked from. */ STATIC word GC_n_rescuing_pages;/* Number of dirty pages we marked from */ /* excludes ptrfree pages, etc. */ mse * GC_mark_stack; mse * GC_mark_stack_limit; size_t GC_mark_stack_size = 0; #ifdef PARALLEL_MARK # include "atomic_ops.h" mse * volatile GC_mark_stack_top; /* Updated only with mark lock held, but read asynchronously. */ volatile AO_t GC_first_nonempty; /* Lowest entry on mark stack */ /* that may be nonempty. */ /* Updated only by initiating */ /* thread. */ #else mse * GC_mark_stack_top; #endif static struct hblk * scan_ptr; mark_state_t GC_mark_state = MS_NONE; GC_bool GC_mark_stack_too_small = FALSE; GC_bool GC_objects_are_marked = FALSE; /* Are there collectable marked */ /* objects in the heap? */ /* Is a collection in progress? Note that this can return true in the */ /* nonincremental case, if a collection has been abandoned and the */ /* mark state is now MS_INVALID. */ GC_bool GC_collection_in_progress(void) { return(GC_mark_state != MS_NONE); } /* clear all mark bits in the header */ void GC_clear_hdr_marks(hdr *hhdr) { size_t last_bit = FINAL_MARK_BIT(hhdr -> hb_sz); # ifdef USE_MARK_BYTES BZERO(hhdr -> hb_marks, MARK_BITS_SZ); hhdr -> hb_marks[last_bit] = 1; # else BZERO(hhdr -> hb_marks, MARK_BITS_SZ*sizeof(word)); set_mark_bit_from_hdr(hhdr, last_bit); # endif hhdr -> hb_n_marks = 0; } /* Set all mark bits in the header. Used for uncollectable blocks. */ void GC_set_hdr_marks(hdr *hhdr) { unsigned i; size_t sz = hhdr -> hb_sz; unsigned n_marks = (unsigned)FINAL_MARK_BIT(sz); # ifdef USE_MARK_BYTES for (i = 0; i <= n_marks; i += (unsigned)MARK_BIT_OFFSET(sz)) { hhdr -> hb_marks[i] = 1; } # else for (i = 0; i < divWORDSZ(n_marks + WORDSZ); ++i) { hhdr -> hb_marks[i] = ONES; } # endif # ifdef MARK_BIT_PER_OBJ hhdr -> hb_n_marks = n_marks - 1; # else hhdr -> hb_n_marks = HBLK_OBJS(sz); # endif } /* * Clear all mark bits associated with block h. */ /*ARGSUSED*/ static void clear_marks_for_block(struct hblk *h, word dummy) { register hdr * hhdr = HDR(h); if (IS_UNCOLLECTABLE(hhdr -> hb_obj_kind)) return; /* Mark bit for these is cleared only once the object is */ /* explicitly deallocated. This either frees the block, or */ /* the bit is cleared once the object is on the free list. */ GC_clear_hdr_marks(hhdr); } /* Slow but general routines for setting/clearing/asking about mark bits */ void GC_set_mark_bit(ptr_t p) { struct hblk *h = HBLKPTR(p); hdr * hhdr = HDR(h); word bit_no = MARK_BIT_NO(p - (ptr_t)h, hhdr -> hb_sz); if (!mark_bit_from_hdr(hhdr, bit_no)) { set_mark_bit_from_hdr(hhdr, bit_no); ++hhdr -> hb_n_marks; } } void GC_clear_mark_bit(ptr_t p) { struct hblk *h = HBLKPTR(p); hdr * hhdr = HDR(h); word bit_no = MARK_BIT_NO(p - (ptr_t)h, hhdr -> hb_sz); if (mark_bit_from_hdr(hhdr, bit_no)) { size_t n_marks; clear_mark_bit_from_hdr(hhdr, bit_no); n_marks = hhdr -> hb_n_marks - 1; # ifdef PARALLEL_MARK if (n_marks != 0 || !GC_parallel) hhdr -> hb_n_marks = n_marks; /* Don't decrement to zero. The counts are approximate due to */ /* concurrency issues, but we need to ensure that a count of */ /* zero implies an empty block. */ # else hhdr -> hb_n_marks = n_marks; # endif } } GC_bool GC_is_marked(ptr_t p) { struct hblk *h = HBLKPTR(p); hdr * hhdr = HDR(h); word bit_no = MARK_BIT_NO(p - (ptr_t)h, hhdr -> hb_sz); return((GC_bool)mark_bit_from_hdr(hhdr, bit_no)); } /* * Clear mark bits in all allocated heap blocks. This invalidates * the marker invariant, and sets GC_mark_state to reflect this. * (This implicitly starts marking to reestablish the invariant.) */ void GC_clear_marks(void) { GC_apply_to_all_blocks(clear_marks_for_block, (word)0); GC_objects_are_marked = FALSE; GC_mark_state = MS_INVALID; scan_ptr = 0; } #ifdef CHECKSUMS extern void GC_check_dirty(void); #endif /* Initiate a garbage collection. Initiates a full collection if the */ /* mark state is invalid. */ void GC_initiate_gc(void) { if (GC_dirty_maintained) GC_read_dirty(); # ifdef STUBBORN_ALLOC GC_read_changed(); # endif # ifdef CHECKSUMS if (GC_dirty_maintained) GC_check_dirty(); # endif GC_n_rescuing_pages = 0; if (GC_mark_state == MS_NONE) { GC_mark_state = MS_PUSH_RESCUERS; } else if (GC_mark_state != MS_INVALID) { ABORT("unexpected state"); } /* else this is really a full collection, and mark */ /* bits are invalid. */ scan_ptr = 0; } #ifdef PARALLEL_MARK STATIC void GC_do_parallel_mark(void); /* initiate parallel marking. */ #endif /* PARALLEL_MARK */ static void alloc_mark_stack(size_t); # if defined(MSWIN32) && (!defined(__GNUC__) || !defined(_WIN64)) \ || defined(USE_PROC_FOR_LIBRARIES) && defined(THREADS) /* Under rare conditions, we may end up marking from nonexistent memory. */ /* Hence we need to be prepared to recover by running GC_mark_some */ /* with a suitable handler in place. */ # define WRAP_MARK_SOME # endif /* Perform a small amount of marking. */ /* We try to touch roughly a page of memory. */ /* Return TRUE if we just finished a mark phase. */ /* Cold_gc_frame is an address inside a GC frame that */ /* remains valid until all marking is complete. */ /* A zero value indicates that it's OK to miss some */ /* register values. */ /* We hold the allocation lock. In the case of */ /* incremental collection, the world may not be stopped.*/ #ifdef WRAP_MARK_SOME /* For win32, this is called after we establish a structured */ /* exception handler, in case Windows unmaps one of our root */ /* segments. See below. In either case, we acquire the */ /* allocator lock long before we get here. */ STATIC GC_bool GC_mark_some_inner(ptr_t cold_gc_frame) #else GC_bool GC_mark_some(ptr_t cold_gc_frame) #endif { switch(GC_mark_state) { case MS_NONE: return(FALSE); case MS_PUSH_RESCUERS: if (GC_mark_stack_top >= GC_mark_stack_limit - INITIAL_MARK_STACK_SIZE/2) { /* Go ahead and mark, even though that might cause us to */ /* see more marked dirty objects later on. Avoid this */ /* in the future. */ GC_mark_stack_too_small = TRUE; MARK_FROM_MARK_STACK(); return(FALSE); } else { scan_ptr = GC_push_next_marked_dirty(scan_ptr); if (scan_ptr == 0) { if (GC_print_stats) { GC_log_printf("Marked from %lu dirty pages\n", (unsigned long)GC_n_rescuing_pages); } GC_push_roots(FALSE, cold_gc_frame); GC_objects_are_marked = TRUE; if (GC_mark_state != MS_INVALID) { GC_mark_state = MS_ROOTS_PUSHED; } } } return(FALSE); case MS_PUSH_UNCOLLECTABLE: if (GC_mark_stack_top >= GC_mark_stack + GC_mark_stack_size/4) { # ifdef PARALLEL_MARK /* Avoid this, since we don't parallelize the marker */ /* here. */ if (GC_parallel) GC_mark_stack_too_small = TRUE; # endif MARK_FROM_MARK_STACK(); return(FALSE); } else { scan_ptr = GC_push_next_marked_uncollectable(scan_ptr); if (scan_ptr == 0) { GC_push_roots(TRUE, cold_gc_frame); GC_objects_are_marked = TRUE; if (GC_mark_state != MS_INVALID) { GC_mark_state = MS_ROOTS_PUSHED; } } } return(FALSE); case MS_ROOTS_PUSHED: # ifdef PARALLEL_MARK /* In the incremental GC case, this currently doesn't */ /* quite do the right thing, since it runs to */ /* completion. On the other hand, starting a */ /* parallel marker is expensive, so perhaps it is */ /* the right thing? */ /* Eventually, incremental marking should run */ /* asynchronously in multiple threads, without grabbing */ /* the allocation lock. */ if (GC_parallel) { GC_do_parallel_mark(); GC_ASSERT(GC_mark_stack_top < (mse *)GC_first_nonempty); GC_mark_stack_top = GC_mark_stack - 1; if (GC_mark_stack_too_small) { alloc_mark_stack(2*GC_mark_stack_size); } if (GC_mark_state == MS_ROOTS_PUSHED) { GC_mark_state = MS_NONE; return(TRUE); } else { return(FALSE); } } # endif if (GC_mark_stack_top >= GC_mark_stack) { MARK_FROM_MARK_STACK(); return(FALSE); } else { GC_mark_state = MS_NONE; if (GC_mark_stack_too_small) { alloc_mark_stack(2*GC_mark_stack_size); } return(TRUE); } case MS_INVALID: case MS_PARTIALLY_INVALID: if (!GC_objects_are_marked) { GC_mark_state = MS_PUSH_UNCOLLECTABLE; return(FALSE); } if (GC_mark_stack_top >= GC_mark_stack) { MARK_FROM_MARK_STACK(); return(FALSE); } if (scan_ptr == 0 && GC_mark_state == MS_INVALID) { /* About to start a heap scan for marked objects. */ /* Mark stack is empty. OK to reallocate. */ if (GC_mark_stack_too_small) { alloc_mark_stack(2*GC_mark_stack_size); } GC_mark_state = MS_PARTIALLY_INVALID; } scan_ptr = GC_push_next_marked(scan_ptr); if (scan_ptr == 0 && GC_mark_state == MS_PARTIALLY_INVALID) { GC_push_roots(TRUE, cold_gc_frame); GC_objects_are_marked = TRUE; if (GC_mark_state != MS_INVALID) { GC_mark_state = MS_ROOTS_PUSHED; } } return(FALSE); default: ABORT("GC_mark_some: bad state"); return(FALSE); } } #if defined(MSWIN32) && defined(__GNUC__) && !defined(_WIN64) typedef struct { EXCEPTION_REGISTRATION ex_reg; void *alt_path; } ext_ex_regn; static EXCEPTION_DISPOSITION mark_ex_handler( struct _EXCEPTION_RECORD *ex_rec, void *est_frame, struct _CONTEXT *context, void *disp_ctxt) { if (ex_rec->ExceptionCode == STATUS_ACCESS_VIOLATION) { ext_ex_regn *xer = (ext_ex_regn *)est_frame; /* Unwind from the inner function assuming the standard */ /* function prologue. */ /* Assumes code has not been compiled with */ /* -fomit-frame-pointer. */ context->Esp = context->Ebp; context->Ebp = *((DWORD *)context->Esp); context->Esp = context->Esp - 8; /* Resume execution at the "real" handler within the */ /* wrapper function. */ context->Eip = (DWORD )(xer->alt_path); return ExceptionContinueExecution; } else { return ExceptionContinueSearch; } } # endif /* __GNUC__ && MSWIN32 */ #ifdef GC_WIN32_THREADS extern GC_bool GC_started_thread_while_stopped(void); /* In win32_threads.c. Did we invalidate mark phase with an */ /* unexpected thread start? */ #endif # ifdef WRAP_MARK_SOME GC_bool GC_mark_some(ptr_t cold_gc_frame) { GC_bool ret_val; # ifdef MSWIN32 # ifndef __GNUC__ /* Windows 98 appears to asynchronously create and remove */ /* writable memory mappings, for reasons we haven't yet */ /* understood. Since we look for writable regions to */ /* determine the root set, we may try to mark from an */ /* address range that disappeared since we started the */ /* collection. Thus we have to recover from faults here. */ /* This code does not appear to be necessary for Windows */ /* 95/NT/2000. Note that this code should never generate */ /* an incremental GC write fault. */ /* It's conceivable that this is the same issue with */ /* terminating threads that we see with Linux and */ /* USE_PROC_FOR_LIBRARIES. */ __try { ret_val = GC_mark_some_inner(cold_gc_frame); } __except (GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION ? EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH) { goto handle_ex; } # ifdef GC_WIN32_THREADS /* With DllMain-based thread tracking, a thread may have */ /* started while we were marking. This is logically equivalent */ /* to the exception case; our results are invalid and we have */ /* to start over. This cannot be prevented since we can't */ /* block in DllMain. */ if (GC_started_thread_while_stopped()) goto handle_ex; # endif rm_handler: return ret_val; # else /* __GNUC__ */ /* Manually install an exception handler since GCC does */ /* not yet support Structured Exception Handling (SEH) on */ /* Win32. */ ext_ex_regn er; er.alt_path = &&handle_ex; er.ex_reg.handler = mark_ex_handler; asm volatile ("movl %%fs:0, %0" : "=r" (er.ex_reg.prev)); asm volatile ("movl %0, %%fs:0" : : "r" (&er)); ret_val = GC_mark_some_inner(cold_gc_frame); /* Prevent GCC from considering the following code unreachable */ /* and thus eliminating it. */ if (er.alt_path == 0) goto handle_ex; rm_handler: /* Uninstall the exception handler */ asm volatile ("mov %0, %%fs:0" : : "r" (er.ex_reg.prev)); return ret_val; # endif /* __GNUC__ */ # else /* !MSWIN32 */ /* Here we are handling the case in which /proc is used for root */ /* finding, and we have threads. We may find a stack for a */ /* thread that is in the process of exiting, and disappears */ /* while we are marking it. This seems extremely difficult to */ /* avoid otherwise. */ if (GC_incremental) WARN("Incremental GC incompatible with /proc roots\n", 0); /* I'm not sure if this could still work ... */ GC_setup_temporary_fault_handler(); if(SETJMP(GC_jmp_buf) != 0) goto handle_ex; ret_val = GC_mark_some_inner(cold_gc_frame); rm_handler: GC_reset_fault_handler(); return ret_val; # endif /* !MSWIN32 */ handle_ex: /* Exception handler starts here for all cases. */ if (GC_print_stats) { GC_log_printf("Caught ACCESS_VIOLATION in marker. " "Memory mapping disappeared.\n"); } /* We have bad roots on the stack. Discard mark stack. */ /* Rescan from marked objects. Redetermine roots. */ GC_invalidate_mark_state(); scan_ptr = 0; ret_val = FALSE; goto rm_handler; /* Back to platform-specific code. */ } #endif /* WRAP_MARK_SOME */ GC_bool GC_mark_stack_empty(void) { return(GC_mark_stack_top < GC_mark_stack); } void GC_invalidate_mark_state(void) { GC_mark_state = MS_INVALID; GC_mark_stack_top = GC_mark_stack-1; } mse * GC_signal_mark_stack_overflow(mse *msp) { GC_mark_state = MS_INVALID; GC_mark_stack_too_small = TRUE; if (GC_print_stats) { GC_log_printf("Mark stack overflow; current size = %lu entries\n", (unsigned long)GC_mark_stack_size); } return(msp - GC_MARK_STACK_DISCARDS); } /* * Mark objects pointed to by the regions described by * mark stack entries between mark_stack and mark_stack_top, * inclusive. Assumes the upper limit of a mark stack entry * is never 0. A mark stack entry never has size 0. * We try to traverse on the order of a hblk of memory before we return. * Caller is responsible for calling this until the mark stack is empty. * Note that this is the most performance critical routine in the * collector. Hence it contains all sorts of ugly hacks to speed * things up. In particular, we avoid procedure calls on the common * path, we take advantage of peculiarities of the mark descriptor * encoding, we optionally maintain a cache for the block address to * header mapping, we prefetch when an object is "grayed", etc. */ mse * GC_mark_from(mse *mark_stack_top, mse *mark_stack, mse *mark_stack_limit) { signed_word credit = HBLKSIZE; /* Remaining credit for marking work */ ptr_t current_p; /* Pointer to current candidate ptr. */ word current; /* Candidate pointer. */ ptr_t limit; /* (Incl) limit of current candidate */ /* range */ word descr; ptr_t greatest_ha = GC_greatest_plausible_heap_addr; ptr_t least_ha = GC_least_plausible_heap_addr; DECLARE_HDR_CACHE; # define SPLIT_RANGE_WORDS 128 /* Must be power of 2. */ GC_objects_are_marked = TRUE; INIT_HDR_CACHE; # ifdef OS2 /* Use untweaked version to circumvent compiler problem */ while (mark_stack_top >= mark_stack && credit >= 0) { # else while ((((ptr_t)mark_stack_top - (ptr_t)mark_stack) | credit) >= 0) { # endif current_p = mark_stack_top -> mse_start; descr = mark_stack_top -> mse_descr; retry: /* current_p and descr describe the current object. */ /* *mark_stack_top is vacant. */ /* The following is 0 only for small objects described by a simple */ /* length descriptor. For many applications this is the common */ /* case, so we try to detect it quickly. */ if (descr & ((~(WORDS_TO_BYTES(SPLIT_RANGE_WORDS) - 1)) | GC_DS_TAGS)) { word tag = descr & GC_DS_TAGS; switch(tag) { case GC_DS_LENGTH: /* Large length. */ /* Process part of the range to avoid pushing too much on the */ /* stack. */ GC_ASSERT(descr < (word)GC_greatest_plausible_heap_addr - (word)GC_least_plausible_heap_addr); # ifdef ENABLE_TRACE if (GC_trace_addr >= current_p && GC_trace_addr < current_p + descr) { GC_log_printf("GC:%u Large section; start %p len %lu\n", (unsigned)GC_gc_no, current_p, (unsigned long) descr); } # endif /* ENABLE_TRACE */ # ifdef PARALLEL_MARK # define SHARE_BYTES 2048 if (descr > SHARE_BYTES && GC_parallel && mark_stack_top < mark_stack_limit - 1) { int new_size = (descr/2) & ~(sizeof(word)-1); mark_stack_top -> mse_start = current_p; mark_stack_top -> mse_descr = new_size + sizeof(word); /* makes sure we handle */ /* misaligned pointers. */ mark_stack_top++; # ifdef ENABLE_TRACE if (GC_trace_addr >= current_p && GC_trace_addr < current_p + descr) { GC_log_printf("GC:%u splitting (parallel) %p at %p\n", (unsigned)GC_gc_no, current_p, current_p + new_size); } # endif /* ENABLE_TRACE */ current_p += new_size; descr -= new_size; goto retry; } # endif /* PARALLEL_MARK */ mark_stack_top -> mse_start = limit = current_p + WORDS_TO_BYTES(SPLIT_RANGE_WORDS-1); mark_stack_top -> mse_descr = descr - WORDS_TO_BYTES(SPLIT_RANGE_WORDS-1); # ifdef ENABLE_TRACE if (GC_trace_addr >= current_p && GC_trace_addr < current_p + descr) { GC_log_printf("GC:%u splitting %p at %p\n", (unsigned)GC_gc_no, current_p, limit); } # endif /* ENABLE_TRACE */ /* Make sure that pointers overlapping the two ranges are */ /* considered. */ limit += sizeof(word) - ALIGNMENT; break; case GC_DS_BITMAP: mark_stack_top--; # ifdef ENABLE_TRACE if (GC_trace_addr >= current_p && GC_trace_addr < current_p + WORDS_TO_BYTES(WORDSZ-2)) { GC_log_printf("GC:%u Tracing from %p bitmap descr %lu\n", (unsigned)GC_gc_no, current_p, (unsigned long) descr); } # endif /* ENABLE_TRACE */ descr &= ~GC_DS_TAGS; credit -= WORDS_TO_BYTES(WORDSZ/2); /* guess */ while (descr != 0) { if ((signed_word)descr < 0) { current = *(word *)current_p; FIXUP_POINTER(current); if ((ptr_t)current >= least_ha && (ptr_t)current < greatest_ha) { PREFETCH((ptr_t)current); # ifdef ENABLE_TRACE if (GC_trace_addr == current_p) { GC_log_printf("GC:%u Considering(3) %p -> %p\n", (unsigned)GC_gc_no, current_p, (ptr_t) current); } # endif /* ENABLE_TRACE */ PUSH_CONTENTS((ptr_t)current, mark_stack_top, mark_stack_limit, current_p, exit1); } } descr <<= 1; current_p += sizeof(word); } continue; case GC_DS_PROC: mark_stack_top--; # ifdef ENABLE_TRACE if (GC_trace_addr >= current_p && GC_base(current_p) != 0 && GC_base(current_p) == GC_base(GC_trace_addr)) { GC_log_printf("GC:%u Tracing from %p proc descr %lu\n", (unsigned)GC_gc_no, current_p, (unsigned long) descr); } # endif /* ENABLE_TRACE */ credit -= GC_PROC_BYTES; mark_stack_top = (*PROC(descr)) ((word *)current_p, mark_stack_top, mark_stack_limit, ENV(descr)); continue; case GC_DS_PER_OBJECT: if ((signed_word)descr >= 0) { /* Descriptor is in the object. */ descr = *(word *)(current_p + descr - GC_DS_PER_OBJECT); } else { /* Descriptor is in type descriptor pointed to by first */ /* word in object. */ ptr_t type_descr = *(ptr_t *)current_p; /* type_descr is either a valid pointer to the descriptor */ /* structure, or this object was on a free list. If it */ /* it was anything but the last object on the free list, */ /* we will misinterpret the next object on the free list as */ /* the type descriptor, and get a 0 GC descriptor, which */ /* is ideal. Unfortunately, we need to check for the last */ /* object case explicitly. */ if (0 == type_descr) { /* Rarely executed. */ mark_stack_top--; continue; } descr = *(word *)(type_descr - (descr + (GC_INDIR_PER_OBJ_BIAS - GC_DS_PER_OBJECT))); } if (0 == descr) { /* Can happen either because we generated a 0 descriptor */ /* or we saw a pointer to a free object. */ mark_stack_top--; continue; } goto retry; default: /* Can't happen. */ limit = 0; /* initialized to prevent warning. */ } } else /* Small object with length descriptor */ { mark_stack_top--; limit = current_p + (word)descr; } # ifdef ENABLE_TRACE if (GC_trace_addr >= current_p && GC_trace_addr < limit) { GC_log_printf("GC:%u Tracing from %p len %lu\n", (int)GC_gc_no, current_p, (unsigned long) descr); } # endif /* ENABLE_TRACE */ /* The simple case in which we're scanning a range. */ GC_ASSERT(!((word)current_p & (ALIGNMENT-1))); credit -= limit - current_p; limit -= sizeof(word); { # define PREF_DIST 4 # ifndef SMALL_CONFIG word deferred; /* Try to prefetch the next pointer to be examined asap. */ /* Empirically, this also seems to help slightly without */ /* prefetches, at least on linux/X86. Presumably this loop */ /* ends up with less register pressure, and gcc thus ends up */ /* generating slightly better code. Overall gcc code quality */ /* for this loop is still not great. */ for(;;) { PREFETCH(limit - PREF_DIST*CACHE_LINE_SIZE); GC_ASSERT(limit >= current_p); deferred = *(word *)limit; FIXUP_POINTER(deferred); limit -= ALIGNMENT; if ((ptr_t)deferred >= least_ha && (ptr_t)deferred < greatest_ha) { PREFETCH((ptr_t)deferred); break; } if (current_p > limit) goto next_object; /* Unroll once, so we don't do too many of the prefetches */ /* based on limit. */ deferred = *(word *)limit; FIXUP_POINTER(deferred); limit -= ALIGNMENT; if ((ptr_t)deferred >= least_ha && (ptr_t)deferred < greatest_ha) { PREFETCH((ptr_t)deferred); break; } if (current_p > limit) goto next_object; } # endif while (current_p <= limit) { /* Empirically, unrolling this loop doesn't help a lot. */ /* Since PUSH_CONTENTS expands to a lot of code, */ /* we don't. */ current = *(word *)current_p; FIXUP_POINTER(current); PREFETCH(current_p + PREF_DIST*CACHE_LINE_SIZE); if ((ptr_t)current >= least_ha && (ptr_t)current < greatest_ha) { /* Prefetch the contents of the object we just pushed. It's */ /* likely we will need them soon. */ PREFETCH((ptr_t)current); # ifdef ENABLE_TRACE if (GC_trace_addr == current_p) { GC_log_printf("GC:%u Considering(1) %p -> %p\n", (unsigned)GC_gc_no, current_p, (ptr_t) current); } # endif /* ENABLE_TRACE */ PUSH_CONTENTS((ptr_t)current, mark_stack_top, mark_stack_limit, current_p, exit2); } current_p += ALIGNMENT; } # ifndef SMALL_CONFIG /* We still need to mark the entry we previously prefetched. */ /* We already know that it passes the preliminary pointer */ /* validity test. */ # ifdef ENABLE_TRACE if (GC_trace_addr == current_p) { GC_log_printf("GC:%u Considering(2) %p -> %p\n", (unsigned)GC_gc_no, current_p, (ptr_t) deferred); } # endif /* ENABLE_TRACE */ PUSH_CONTENTS((ptr_t)deferred, mark_stack_top, mark_stack_limit, current_p, exit4); next_object:; # endif } } return mark_stack_top; } #ifdef PARALLEL_MARK STATIC GC_bool GC_help_wanted = FALSE; /* Protected by mark lock */ STATIC unsigned GC_helper_count = 0; /* Number of running helpers. */ /* Protected by mark lock */ STATIC unsigned GC_active_count = 0; /* Number of active helpers. */ /* Protected by mark lock */ /* May increase and decrease */ /* within each mark cycle. But */ /* once it returns to 0, it */ /* stays zero for the cycle. */ word GC_mark_no = 0; #define LOCAL_MARK_STACK_SIZE HBLKSIZE /* Under normal circumstances, this is big enough to guarantee */ /* We don't overflow half of it in a single call to */ /* GC_mark_from. */ /* Steal mark stack entries starting at mse low into mark stack local */ /* until we either steal mse high, or we have max entries. */ /* Return a pointer to the top of the local mark stack. */ /* *next is replaced by a pointer to the next unscanned mark stack */ /* entry. */ STATIC mse * GC_steal_mark_stack(mse * low, mse * high, mse * local, unsigned max, mse **next) { mse *p; mse *top = local - 1; unsigned i = 0; GC_ASSERT(high >= low-1 && (word)(high - low + 1) <= GC_mark_stack_size); for (p = low; p <= high && i <= max; ++p) { word descr = AO_load((volatile AO_t *) &(p -> mse_descr)); if (descr != 0) { /* Must be ordered after read of descr: */ AO_store_release_write((volatile AO_t *) &(p -> mse_descr), 0); /* More than one thread may get this entry, but that's only */ /* a minor performance problem. */ ++top; top -> mse_descr = descr; top -> mse_start = p -> mse_start; GC_ASSERT((top -> mse_descr & GC_DS_TAGS) != GC_DS_LENGTH || top -> mse_descr < (word)GC_greatest_plausible_heap_addr - (word)GC_least_plausible_heap_addr); /* If this is a big object, count it as */ /* size/256 + 1 objects. */ ++i; if ((descr & GC_DS_TAGS) == GC_DS_LENGTH) i += (int)(descr >> 8); } } *next = p; return top; } /* Copy back a local mark stack. */ /* low and high are inclusive bounds. */ STATIC void GC_return_mark_stack(mse * low, mse * high) { mse * my_top; mse * my_start; size_t stack_size; if (high < low) return; stack_size = high - low + 1; GC_acquire_mark_lock(); my_top = GC_mark_stack_top; /* Concurrent modification impossible. */ my_start = my_top + 1; if (my_start - GC_mark_stack + stack_size > GC_mark_stack_size) { if (GC_print_stats) { GC_log_printf("No room to copy back mark stack\n"); } GC_mark_state = MS_INVALID; GC_mark_stack_too_small = TRUE; /* We drop the local mark stack. We'll fix things later. */ } else { BCOPY(low, my_start, stack_size * sizeof(mse)); GC_ASSERT((mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) == my_top); AO_store_release_write((volatile AO_t *)(&GC_mark_stack_top), (AO_t)(my_top + stack_size)); /* Ensures visibility of previously written stack contents. */ } GC_release_mark_lock(); GC_notify_all_marker(); } /* Mark from the local mark stack. */ /* On return, the local mark stack is empty. */ /* But this may be achieved by copying the */ /* local mark stack back into the global one. */ STATIC void GC_do_local_mark(mse *local_mark_stack, mse *local_top) { unsigned n; # define N_LOCAL_ITERS 1 # ifdef GC_ASSERTIONS /* Make sure we don't hold mark lock. */ GC_acquire_mark_lock(); GC_release_mark_lock(); # endif for (;;) { for (n = 0; n < N_LOCAL_ITERS; ++n) { local_top = GC_mark_from(local_top, local_mark_stack, local_mark_stack + LOCAL_MARK_STACK_SIZE); if (local_top < local_mark_stack) return; if (local_top - local_mark_stack >= LOCAL_MARK_STACK_SIZE/2) { GC_return_mark_stack(local_mark_stack, local_top); return; } } if ((mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) < (mse *)AO_load(&GC_first_nonempty) && GC_active_count < GC_helper_count && local_top > local_mark_stack + 1) { /* Try to share the load, since the main stack is empty, */ /* and helper threads are waiting for a refill. */ /* The entries near the bottom of the stack are likely */ /* to require more work. Thus we return those, eventhough */ /* it's harder. */ mse * new_bottom = local_mark_stack + (local_top - local_mark_stack)/2; GC_ASSERT(new_bottom > local_mark_stack && new_bottom < local_top); GC_return_mark_stack(local_mark_stack, new_bottom - 1); memmove(local_mark_stack, new_bottom, (local_top - new_bottom + 1) * sizeof(mse)); local_top -= (new_bottom - local_mark_stack); } } } #define ENTRIES_TO_GET 5 long GC_markers = 2; /* Normally changed by thread-library- */ /* -specific code. */ /* Mark using the local mark stack until the global mark stack is empty */ /* and there are no active workers. Update GC_first_nonempty to reflect */ /* progress. */ /* Caller does not hold mark lock. */ /* Caller has already incremented GC_helper_count. We decrement it, */ /* and maintain GC_active_count. */ STATIC void GC_mark_local(mse *local_mark_stack, int id) { mse * my_first_nonempty; GC_acquire_mark_lock(); GC_active_count++; my_first_nonempty = (mse *)AO_load(&GC_first_nonempty); GC_ASSERT((mse *)AO_load(&GC_first_nonempty) >= GC_mark_stack && (mse *)AO_load(&GC_first_nonempty) <= (mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) + 1); if (GC_print_stats == VERBOSE) GC_log_printf("Starting mark helper %lu\n", (unsigned long)id); GC_release_mark_lock(); for (;;) { size_t n_on_stack; unsigned n_to_get; mse * my_top; mse * local_top; mse * global_first_nonempty = (mse *)AO_load(&GC_first_nonempty); GC_ASSERT(my_first_nonempty >= GC_mark_stack && my_first_nonempty <= (mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) + 1); GC_ASSERT(global_first_nonempty >= GC_mark_stack && global_first_nonempty <= (mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) + 1); if (my_first_nonempty < global_first_nonempty) { my_first_nonempty = global_first_nonempty; } else if (global_first_nonempty < my_first_nonempty) { AO_compare_and_swap(&GC_first_nonempty, (AO_t) global_first_nonempty, (AO_t) my_first_nonempty); /* If this fails, we just go ahead, without updating */ /* GC_first_nonempty. */ } /* Perhaps we should also update GC_first_nonempty, if it */ /* is less. But that would require using atomic updates. */ my_top = (mse *)AO_load_acquire((volatile AO_t *)(&GC_mark_stack_top)); n_on_stack = my_top - my_first_nonempty + 1; if (0 == n_on_stack) { GC_acquire_mark_lock(); my_top = GC_mark_stack_top; /* Asynchronous modification impossible here, */ /* since we hold mark lock. */ n_on_stack = my_top - my_first_nonempty + 1; if (0 == n_on_stack) { GC_active_count--; GC_ASSERT(GC_active_count <= GC_helper_count); /* Other markers may redeposit objects */ /* on the stack. */ if (0 == GC_active_count) GC_notify_all_marker(); while (GC_active_count > 0 && (mse *)AO_load(&GC_first_nonempty) > GC_mark_stack_top) { /* We will be notified if either GC_active_count */ /* reaches zero, or if more objects are pushed on */ /* the global mark stack. */ GC_wait_marker(); } if (GC_active_count == 0 && (mse *)AO_load(&GC_first_nonempty) > GC_mark_stack_top) { GC_bool need_to_notify = FALSE; /* The above conditions can't be falsified while we */ /* hold the mark lock, since neither */ /* GC_active_count nor GC_mark_stack_top can */ /* change. GC_first_nonempty can only be */ /* incremented asynchronously. Thus we know that */ /* both conditions actually held simultaneously. */ GC_helper_count--; if (0 == GC_helper_count) need_to_notify = TRUE; if (GC_print_stats == VERBOSE) GC_log_printf( "Finished mark helper %lu\n", (unsigned long)id); GC_release_mark_lock(); if (need_to_notify) GC_notify_all_marker(); return; } /* else there's something on the stack again, or */ /* another helper may push something. */ GC_active_count++; GC_ASSERT(GC_active_count > 0); GC_release_mark_lock(); continue; } else { GC_release_mark_lock(); } } n_to_get = ENTRIES_TO_GET; if (n_on_stack < 2 * ENTRIES_TO_GET) n_to_get = 1; local_top = GC_steal_mark_stack(my_first_nonempty, my_top, local_mark_stack, n_to_get, &my_first_nonempty); GC_ASSERT(my_first_nonempty >= GC_mark_stack && my_first_nonempty <= (mse *)AO_load((volatile AO_t *)(&GC_mark_stack_top)) + 1); GC_do_local_mark(local_mark_stack, local_top); } } /* Perform Parallel mark. */ /* We hold the GC lock, not the mark lock. */ /* Currently runs until the mark stack is */ /* empty. */ STATIC void GC_do_parallel_mark(void) { mse local_mark_stack[LOCAL_MARK_STACK_SIZE]; GC_acquire_mark_lock(); GC_ASSERT(I_HOLD_LOCK()); /* This could be a GC_ASSERT, but it seems safer to keep it on */ /* all the time, especially since it's cheap. */ if (GC_help_wanted || GC_active_count != 0 || GC_helper_count != 0) ABORT("Tried to start parallel mark in bad state"); if (GC_print_stats == VERBOSE) GC_log_printf("Starting marking for mark phase number %lu\n", (unsigned long)GC_mark_no); GC_first_nonempty = (AO_t)GC_mark_stack; GC_active_count = 0; GC_helper_count = 1; GC_help_wanted = TRUE; GC_release_mark_lock(); GC_notify_all_marker(); /* Wake up potential helpers. */ GC_mark_local(local_mark_stack, 0); GC_acquire_mark_lock(); GC_help_wanted = FALSE; /* Done; clean up. */ while (GC_helper_count > 0) GC_wait_marker(); /* GC_helper_count cannot be incremented while GC_help_wanted == FALSE */ if (GC_print_stats == VERBOSE) GC_log_printf( "Finished marking for mark phase number %lu\n", (unsigned long)GC_mark_no); GC_mark_no++; GC_release_mark_lock(); GC_notify_all_marker(); } /* Try to help out the marker, if it's running. */ /* We do not hold the GC lock, but the requestor does. */ void GC_help_marker(word my_mark_no) { mse local_mark_stack[LOCAL_MARK_STACK_SIZE]; unsigned my_id; if (!GC_parallel) return; GC_acquire_mark_lock(); while (GC_mark_no < my_mark_no || (!GC_help_wanted && GC_mark_no == my_mark_no)) { GC_wait_marker(); } my_id = GC_helper_count; if (GC_mark_no != my_mark_no || my_id >= (unsigned)GC_markers) { /* Second test is useful only if original threads can also */ /* act as helpers. Under Linux they can't. */ GC_release_mark_lock(); return; } GC_helper_count = my_id + 1; GC_release_mark_lock(); GC_mark_local(local_mark_stack, my_id); /* GC_mark_local decrements GC_helper_count. */ } #endif /* PARALLEL_MARK */ /* Allocate or reallocate space for mark stack of size n entries. */ /* May silently fail. */ static void alloc_mark_stack(size_t n) { mse * new_stack = (mse *)GC_scratch_alloc(n * sizeof(struct GC_ms_entry)); # ifdef GWW_VDB /* Don't recycle a stack segment obtained with the wrong flags. */ /* Win32 GetWriteWatch requires the right kind of memory. */ static GC_bool GC_incremental_at_stack_alloc = 0; GC_bool recycle_old = (!GC_incremental || GC_incremental_at_stack_alloc); GC_incremental_at_stack_alloc = GC_incremental; # else # define recycle_old 1 # endif GC_mark_stack_too_small = FALSE; if (GC_mark_stack_size != 0) { if (new_stack != 0) { if (recycle_old) { /* Recycle old space */ size_t page_offset = (word)GC_mark_stack & (GC_page_size - 1); size_t size = GC_mark_stack_size * sizeof(struct GC_ms_entry); size_t displ = 0; if (0 != page_offset) displ = GC_page_size - page_offset; size = (size - displ) & ~(GC_page_size - 1); if (size > 0) { GC_add_to_heap((struct hblk *) ((word)GC_mark_stack + displ), (word)size); } } GC_mark_stack = new_stack; GC_mark_stack_size = n; GC_mark_stack_limit = new_stack + n; if (GC_print_stats) { GC_log_printf("Grew mark stack to %lu frames\n", (unsigned long) GC_mark_stack_size); } } else { if (GC_print_stats) { GC_log_printf("Failed to grow mark stack to %lu frames\n", (unsigned long) n); } } } else { if (new_stack == 0) { GC_err_printf("No space for mark stack\n"); EXIT(); } GC_mark_stack = new_stack; GC_mark_stack_size = n; GC_mark_stack_limit = new_stack + n; } GC_mark_stack_top = GC_mark_stack-1; } void GC_mark_init(void) { alloc_mark_stack(INITIAL_MARK_STACK_SIZE); } /* * Push all locations between b and t onto the mark stack. * b is the first location to be checked. t is one past the last * location to be checked. * Should only be used if there is no possibility of mark stack * overflow. */ void GC_push_all(ptr_t bottom, ptr_t top) { register word length; bottom = (ptr_t)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1)); top = (ptr_t)(((word) top) & ~(ALIGNMENT-1)); if (top == 0 || bottom == top) return; GC_mark_stack_top++; if (GC_mark_stack_top >= GC_mark_stack_limit) { ABORT("unexpected mark stack overflow"); } length = top - bottom; # if GC_DS_TAGS > ALIGNMENT - 1 length += GC_DS_TAGS; length &= ~GC_DS_TAGS; # endif GC_mark_stack_top -> mse_start = bottom; GC_mark_stack_top -> mse_descr = length; } /* * Analogous to the above, but push only those pages h with dirty_fn(h) != 0. * We use push_fn to actually push the block. * Used both to selectively push dirty pages, or to push a block * in piecemeal fashion, to allow for more marking concurrency. * Will not overflow mark stack if push_fn pushes a small fixed number * of entries. (This is invoked only if push_fn pushes a single entry, * or if it marks each object before pushing it, thus ensuring progress * in the event of a stack overflow.) */ void GC_push_selected(ptr_t bottom, ptr_t top, int (*dirty_fn) (struct hblk *), void (*push_fn) (ptr_t, ptr_t)) { struct hblk * h; bottom = (ptr_t)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1)); top = (ptr_t)(((word) top) & ~(ALIGNMENT-1)); if (top == 0 || bottom == top) return; h = HBLKPTR(bottom + HBLKSIZE); if (top <= (ptr_t) h) { if ((*dirty_fn)(h-1)) { (*push_fn)(bottom, top); } return; } if ((*dirty_fn)(h-1)) { (*push_fn)(bottom, (ptr_t)h); } while ((ptr_t)(h+1) <= top) { if ((*dirty_fn)(h)) { if ((word)(GC_mark_stack_top - GC_mark_stack) > 3 * GC_mark_stack_size / 4) { /* Danger of mark stack overflow */ (*push_fn)((ptr_t)h, top); return; } else { (*push_fn)((ptr_t)h, (ptr_t)(h+1)); } } h++; } if ((ptr_t)h != top) { if ((*dirty_fn)(h)) { (*push_fn)((ptr_t)h, top); } } if (GC_mark_stack_top >= GC_mark_stack_limit) { ABORT("unexpected mark stack overflow"); } } # ifndef SMALL_CONFIG void GC_push_conditional(ptr_t bottom, ptr_t top, GC_bool all) { if (all) { if (GC_dirty_maintained) { # ifdef PROC_VDB /* Pages that were never dirtied cannot contain pointers */ GC_push_selected(bottom, top, GC_page_was_ever_dirty, GC_push_all); # else GC_push_all(bottom, top); # endif } else { GC_push_all(bottom, top); } } else { GC_push_selected(bottom, top, GC_page_was_dirty, GC_push_all); } } #endif # if defined(MSWIN32) || defined(MSWINCE) void __cdecl GC_push_one(word p) # else void GC_push_one(word p) # endif { GC_PUSH_ONE_STACK(p, MARKED_FROM_REGISTER); } /*ARGSUSED*/ struct GC_ms_entry *GC_mark_and_push(void *obj, mse *mark_stack_ptr, mse *mark_stack_limit, void **src) { hdr * hhdr; PREFETCH(obj); GET_HDR(obj, hhdr); if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr),FALSE)) { if (GC_all_interior_pointers) { hhdr = GC_find_header(GC_base(obj)); if (hhdr == 0) { GC_ADD_TO_BLACK_LIST_NORMAL(obj, (ptr_t)src); return mark_stack_ptr; } } else { GC_ADD_TO_BLACK_LIST_NORMAL(obj, (ptr_t)src); return mark_stack_ptr; } } if (EXPECT(HBLK_IS_FREE(hhdr),0)) { GC_ADD_TO_BLACK_LIST_NORMAL(obj, (ptr_t)src); return mark_stack_ptr; } PUSH_CONTENTS_HDR(obj, mark_stack_ptr /* modified */, mark_stack_limit, (ptr_t)src, was_marked, hhdr, TRUE); was_marked: return mark_stack_ptr; } /* Mark and push (i.e. gray) a single object p onto the main */ /* mark stack. Consider p to be valid if it is an interior */ /* pointer. */ /* The object p has passed a preliminary pointer validity */ /* test, but we do not definitely know whether it is valid. */ /* Mark bits are NOT atomically updated. Thus this must be the */ /* only thread setting them. */ # if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS) void GC_mark_and_push_stack(ptr_t p, ptr_t source) # else void GC_mark_and_push_stack(ptr_t p) # define source ((ptr_t)0) # endif { hdr * hhdr; ptr_t r = p; PREFETCH(p); GET_HDR(p, hhdr); if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr),FALSE)) { if (hhdr != 0) { r = GC_base(p); hhdr = HDR(r); } if (hhdr == 0) { GC_ADD_TO_BLACK_LIST_STACK(p, source); return; } } if (EXPECT(HBLK_IS_FREE(hhdr),0)) { GC_ADD_TO_BLACK_LIST_NORMAL(p, source); return; } # if defined(MANUAL_VDB) && defined(THREADS) /* Pointer is on the stack. We may have dirtied the object */ /* it points to, but not yet have called GC_dirty(); */ GC_dirty(p); /* Implicitly affects entire object. */ # endif PUSH_CONTENTS_HDR(r, GC_mark_stack_top, GC_mark_stack_limit, source, mark_and_push_exit, hhdr, FALSE); mark_and_push_exit: ; /* We silently ignore pointers to near the end of a block, */ /* which is very mildly suboptimal. */ /* FIXME: We should probably add a header word to address */ /* this. */ } # ifdef TRACE_BUF # define TRACE_ENTRIES 1000 struct trace_entry { char * kind; word gc_no; word bytes_allocd; word arg1; word arg2; } GC_trace_buf[TRACE_ENTRIES]; int GC_trace_buf_ptr = 0; void GC_add_trace_entry(char *kind, word arg1, word arg2) { GC_trace_buf[GC_trace_buf_ptr].kind = kind; GC_trace_buf[GC_trace_buf_ptr].gc_no = GC_gc_no; GC_trace_buf[GC_trace_buf_ptr].bytes_allocd = GC_bytes_allocd; GC_trace_buf[GC_trace_buf_ptr].arg1 = arg1 ^ 0x80000000; GC_trace_buf[GC_trace_buf_ptr].arg2 = arg2 ^ 0x80000000; GC_trace_buf_ptr++; if (GC_trace_buf_ptr >= TRACE_ENTRIES) GC_trace_buf_ptr = 0; } void GC_print_trace(word gc_no, GC_bool lock) { int i; struct trace_entry *p; if (lock) LOCK(); for (i = GC_trace_buf_ptr-1; i != GC_trace_buf_ptr; i--) { if (i < 0) i = TRACE_ENTRIES-1; p = GC_trace_buf + i; if (p -> gc_no < gc_no || p -> kind == 0) return; printf("Trace:%s (gc:%u,bytes:%lu) 0x%X, 0x%X\n", p -> kind, (unsigned)p -> gc_no, (unsigned long)p -> bytes_allocd, (p -> arg1) ^ 0x80000000, (p -> arg2) ^ 0x80000000); } printf("Trace incomplete\n"); if (lock) UNLOCK(); } # endif /* TRACE_BUF */ /* * A version of GC_push_all that treats all interior pointers as valid * and scans the entire region immediately, in case the contents * change. */ void GC_push_all_eager(ptr_t bottom, ptr_t top) { word * b = (word *)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1)); word * t = (word *)(((word) top) & ~(ALIGNMENT-1)); register word *p; register word q; register word *lim; register ptr_t greatest_ha = GC_greatest_plausible_heap_addr; register ptr_t least_ha = GC_least_plausible_heap_addr; # define GC_greatest_plausible_heap_addr greatest_ha # define GC_least_plausible_heap_addr least_ha if (top == 0) return; /* check all pointers in range and push if they appear */ /* to be valid. */ lim = t - 1 /* longword */; for (p = b; p <= lim; p = (word *)(((ptr_t)p) + ALIGNMENT)) { q = *p; GC_PUSH_ONE_STACK(q, p); } # undef GC_greatest_plausible_heap_addr # undef GC_least_plausible_heap_addr } #ifndef THREADS /* * A version of GC_push_all that treats all interior pointers as valid * and scans part of the area immediately, to make sure that saved * register values are not lost. * Cold_gc_frame delimits the stack section that must be scanned * eagerly. A zero value indicates that no eager scanning is needed. * We don't need to worry about the MANUAL_VDB case here, since this * is only called in the single-threaded case. We assume that we * cannot collect between an assignment and the corresponding * GC_dirty() call. */ void GC_push_all_stack_partially_eager(ptr_t bottom, ptr_t top, ptr_t cold_gc_frame) { if (!NEED_FIXUP_POINTER && GC_all_interior_pointers) { /* Push the hot end of the stack eagerly, so that register values */ /* saved inside GC frames are marked before they disappear. */ /* The rest of the marking can be deferred until later. */ if (0 == cold_gc_frame) { GC_push_all_stack(bottom, top); return; } GC_ASSERT(bottom <= cold_gc_frame && cold_gc_frame <= top); # ifdef STACK_GROWS_DOWN GC_push_all(cold_gc_frame - sizeof(ptr_t), top); GC_push_all_eager(bottom, cold_gc_frame); # else /* STACK_GROWS_UP */ GC_push_all(bottom, cold_gc_frame + sizeof(ptr_t)); GC_push_all_eager(cold_gc_frame, top); # endif /* STACK_GROWS_UP */ } else { GC_push_all_eager(bottom, top); } # ifdef TRACE_BUF GC_add_trace_entry("GC_push_all_stack", bottom, top); # endif } #endif /* !THREADS */ void GC_push_all_stack(ptr_t bottom, ptr_t top) { # if defined(THREADS) && defined(MPROTECT_VDB) GC_push_all_eager(bottom, top); # else if (!NEED_FIXUP_POINTER && GC_all_interior_pointers) { GC_push_all(bottom, top); } else { GC_push_all_eager(bottom, top); } # endif } #if !defined(SMALL_CONFIG) && !defined(USE_MARK_BYTES) && \ defined(MARK_BIT_PER_GRANULE) # if GC_GRANULE_WORDS == 1 # define USE_PUSH_MARKED_ACCELERATORS # define PUSH_GRANULE(q) \ { word qcontents = (q)[0]; \ GC_PUSH_ONE_HEAP(qcontents, (q)); } # elif GC_GRANULE_WORDS == 2 # define USE_PUSH_MARKED_ACCELERATORS # define PUSH_GRANULE(q) \ { word qcontents = (q)[0]; \ GC_PUSH_ONE_HEAP(qcontents, (q)); \ qcontents = (q)[1]; \ GC_PUSH_ONE_HEAP(qcontents, (q)+1); } # elif GC_GRANULE_WORDS == 4 # define USE_PUSH_MARKED_ACCELERATORS # define PUSH_GRANULE(q) \ { word qcontents = (q)[0]; \ GC_PUSH_ONE_HEAP(qcontents, (q)); \ qcontents = (q)[1]; \ GC_PUSH_ONE_HEAP(qcontents, (q)+1); \ qcontents = (q)[2]; \ GC_PUSH_ONE_HEAP(qcontents, (q)+2); \ qcontents = (q)[3]; \ GC_PUSH_ONE_HEAP(qcontents, (q)+3); } # endif #endif #ifdef USE_PUSH_MARKED_ACCELERATORS /* Push all objects reachable from marked objects in the given block */ /* containing objects of size 1 granule. */ void GC_push_marked1(struct hblk *h, hdr *hhdr) { word * mark_word_addr = &(hhdr->hb_marks[0]); word *p; word *plim; word *q; word mark_word; /* Allow registers to be used for some frequently acccessed */ /* global variables. Otherwise aliasing issues are likely */ /* to prevent that. */ ptr_t greatest_ha = GC_greatest_plausible_heap_addr; ptr_t least_ha = GC_least_plausible_heap_addr; mse * mark_stack_top = GC_mark_stack_top; mse * mark_stack_limit = GC_mark_stack_limit; # define GC_mark_stack_top mark_stack_top # define GC_mark_stack_limit mark_stack_limit # define GC_greatest_plausible_heap_addr greatest_ha # define GC_least_plausible_heap_addr least_ha p = (word *)(h->hb_body); plim = (word *)(((word)h) + HBLKSIZE); /* go through all words in block */ while( p < plim ) { mark_word = *mark_word_addr++; q = p; while(mark_word != 0) { if (mark_word & 1) { PUSH_GRANULE(q); } q += GC_GRANULE_WORDS; mark_word >>= 1; } p += WORDSZ*GC_GRANULE_WORDS; } # undef GC_greatest_plausible_heap_addr # undef GC_least_plausible_heap_addr # undef GC_mark_stack_top # undef GC_mark_stack_limit GC_mark_stack_top = mark_stack_top; } #ifndef UNALIGNED /* Push all objects reachable from marked objects in the given block */ /* of size 2 (granules) objects. */ void GC_push_marked2(struct hblk *h, hdr *hhdr) { word * mark_word_addr = &(hhdr->hb_marks[0]); word *p; word *plim; word *q; word mark_word; ptr_t greatest_ha = GC_greatest_plausible_heap_addr; ptr_t least_ha = GC_least_plausible_heap_addr; mse * mark_stack_top = GC_mark_stack_top; mse * mark_stack_limit = GC_mark_stack_limit; # define GC_mark_stack_top mark_stack_top # define GC_mark_stack_limit mark_stack_limit # define GC_greatest_plausible_heap_addr greatest_ha # define GC_least_plausible_heap_addr least_ha p = (word *)(h->hb_body); plim = (word *)(((word)h) + HBLKSIZE); /* go through all words in block */ while( p < plim ) { mark_word = *mark_word_addr++; q = p; while(mark_word != 0) { if (mark_word & 1) { PUSH_GRANULE(q); PUSH_GRANULE(q + GC_GRANULE_WORDS); } q += 2 * GC_GRANULE_WORDS; mark_word >>= 2; } p += WORDSZ*GC_GRANULE_WORDS; } # undef GC_greatest_plausible_heap_addr # undef GC_least_plausible_heap_addr # undef GC_mark_stack_top # undef GC_mark_stack_limit GC_mark_stack_top = mark_stack_top; } # if GC_GRANULE_WORDS < 4 /* Push all objects reachable from marked objects in the given block */ /* of size 4 (granules) objects. */ /* There is a risk of mark stack overflow here. But we handle that. */ /* And only unmarked objects get pushed, so it's not very likely. */ void GC_push_marked4(struct hblk *h, hdr *hhdr) { word * mark_word_addr = &(hhdr->hb_marks[0]); word *p; word *plim; word *q; word mark_word; ptr_t greatest_ha = GC_greatest_plausible_heap_addr; ptr_t least_ha = GC_least_plausible_heap_addr; mse * mark_stack_top = GC_mark_stack_top; mse * mark_stack_limit = GC_mark_stack_limit; # define GC_mark_stack_top mark_stack_top # define GC_mark_stack_limit mark_stack_limit # define GC_greatest_plausible_heap_addr greatest_ha # define GC_least_plausible_heap_addr least_ha p = (word *)(h->hb_body); plim = (word *)(((word)h) + HBLKSIZE); /* go through all words in block */ while( p < plim ) { mark_word = *mark_word_addr++; q = p; while(mark_word != 0) { if (mark_word & 1) { PUSH_GRANULE(q); PUSH_GRANULE(q + GC_GRANULE_WORDS); PUSH_GRANULE(q + 2*GC_GRANULE_WORDS); PUSH_GRANULE(q + 3*GC_GRANULE_WORDS); } q += 4 * GC_GRANULE_WORDS; mark_word >>= 4; } p += WORDSZ*GC_GRANULE_WORDS; } # undef GC_greatest_plausible_heap_addr # undef GC_least_plausible_heap_addr # undef GC_mark_stack_top # undef GC_mark_stack_limit GC_mark_stack_top = mark_stack_top; } #endif /* GC_GRANULE_WORDS < 4 */ #endif /* UNALIGNED */ #endif /* USE_PUSH_MARKED_ACCELERATORS */ /* Push all objects reachable from marked objects in the given block */ void GC_push_marked(struct hblk *h, hdr *hhdr) { size_t sz = hhdr -> hb_sz; word descr = hhdr -> hb_descr; ptr_t p; word bit_no; ptr_t lim; mse * GC_mark_stack_top_reg; mse * mark_stack_limit = GC_mark_stack_limit; /* Some quick shortcuts: */ if ((0 | GC_DS_LENGTH) == descr) return; if (GC_block_empty(hhdr)/* nothing marked */) return; GC_n_rescuing_pages++; GC_objects_are_marked = TRUE; if (sz > MAXOBJBYTES) { lim = h -> hb_body; } else { lim = (h + 1)->hb_body - sz; } switch(BYTES_TO_GRANULES(sz)) { # if defined(USE_PUSH_MARKED_ACCELERATORS) case 1: GC_push_marked1(h, hhdr); break; # if !defined(UNALIGNED) case 2: GC_push_marked2(h, hhdr); break; # if GC_GRANULE_WORDS < 4 case 4: GC_push_marked4(h, hhdr); break; # endif # endif # endif default: GC_mark_stack_top_reg = GC_mark_stack_top; for (p = h -> hb_body, bit_no = 0; p <= lim; p += sz, bit_no += MARK_BIT_OFFSET(sz)) { if (mark_bit_from_hdr(hhdr, bit_no)) { /* Mark from fields inside the object */ PUSH_OBJ(p, hhdr, GC_mark_stack_top_reg, mark_stack_limit); } } GC_mark_stack_top = GC_mark_stack_top_reg; } } #ifndef SMALL_CONFIG /* Test whether any page in the given block is dirty */ STATIC GC_bool GC_block_was_dirty(struct hblk *h, hdr *hhdr) { size_t sz = hhdr -> hb_sz; if (sz <= MAXOBJBYTES) { return(GC_page_was_dirty(h)); } else { ptr_t p = (ptr_t)h; while (p < (ptr_t)h + sz) { if (GC_page_was_dirty((struct hblk *)p)) return(TRUE); p += HBLKSIZE; } return(FALSE); } } #endif /* SMALL_CONFIG */ /* Similar to GC_push_marked, but skip over unallocated blocks */ /* and return address of next plausible block. */ struct hblk * GC_push_next_marked(struct hblk *h) { hdr * hhdr = HDR(h); if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr) || HBLK_IS_FREE(hhdr), FALSE)) { h = GC_next_used_block(h); if (h == 0) return(0); hhdr = GC_find_header((ptr_t)h); } GC_push_marked(h, hhdr); return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz)); } #ifndef SMALL_CONFIG /* Identical to above, but mark only from dirty pages */ struct hblk * GC_push_next_marked_dirty(struct hblk *h) { hdr * hhdr = HDR(h); if (!GC_dirty_maintained) { ABORT("dirty bits not set up"); } for (;;) { if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr) || HBLK_IS_FREE(hhdr), FALSE)) { h = GC_next_used_block(h); if (h == 0) return(0); hhdr = GC_find_header((ptr_t)h); } # ifdef STUBBORN_ALLOC if (hhdr -> hb_obj_kind == STUBBORN) { if (GC_page_was_changed(h) && GC_block_was_dirty(h, hhdr)) { break; } } else { if (GC_block_was_dirty(h, hhdr)) break; } # else if (GC_block_was_dirty(h, hhdr)) break; # endif h += OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz); hhdr = HDR(h); } GC_push_marked(h, hhdr); return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz)); } #endif /* Similar to above, but for uncollectable pages. Needed since we */ /* do not clear marks for such pages, even for full collections. */ struct hblk * GC_push_next_marked_uncollectable(struct hblk *h) { hdr * hhdr = HDR(h); for (;;) { if (EXPECT(IS_FORWARDING_ADDR_OR_NIL(hhdr) || HBLK_IS_FREE(hhdr), FALSE)) { h = GC_next_used_block(h); if (h == 0) return(0); hhdr = GC_find_header((ptr_t)h); } if (hhdr -> hb_obj_kind == UNCOLLECTABLE) break; h += OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz); hhdr = HDR(h); } GC_push_marked(h, hhdr); return(h + OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz)); }