X-Git-Url: http://wien.tomnetworks.com/gitweb/?p=hs-boehmgc.git;a=blobdiff_plain;f=gc-7.2%2Fmark.c;fp=gc-7.2%2Fmark.c;h=cc8dfde9e01eb531b5f5c1ed4daa23cfb281e23a;hp=0000000000000000000000000000000000000000;hb=324587ba93dc77f37406d41fd2a20d0e0d94fb1d;hpb=2a4ea609491b225a1ceb06da70396e93916f137a diff --git a/gc-7.2/mark.c b/gc-7.2/mark.c new file mode 100644 index 0000000..cc8dfde --- /dev/null +++ b/gc-7.2/mark.c @@ -0,0 +1,1852 @@ +/* + * 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 "private/gc_pmark.h" + +#include + +#if defined(MSWIN32) && defined(__GNUC__) +# include +#endif + +/* We put this here to minimize the risk of inlining. */ +/*VARARGS*/ +#if defined(__BORLANDC__) || defined(__WATCOMC__) || defined(__CC_ARM) + /*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. */ +volatile word GC_noop_sink; +GC_API void GC_CALL GC_noop1(word x) +{ + GC_noop_sink = x; +} + +/* mark_proc GC_mark_procs[MAX_MARK_PROCS] = {0} -- declared in gc_priv.h */ + +GC_INNER 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. */ +GC_INNER 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 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 +# define GC_N_KINDS_INITIAL_VALUE 5 +# else +# define GC_N_KINDS_INITIAL_VALUE 4 +# endif +# else +# ifdef STUBBORN_ALLOC +# define GC_N_KINDS_INITIAL_VALUE 4 +# else +# define GC_N_KINDS_INITIAL_VALUE 3 +# endif +# endif + +GC_INNER unsigned GC_n_kinds = GC_N_KINDS_INITIAL_VALUE; + +# 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 = 0; + /* Number of dirty pages we marked from */ + /* excludes ptrfree pages, etc. */ + +GC_INNER mse * GC_mark_stack = NULL; +GC_INNER mse * GC_mark_stack_limit = NULL; +GC_INNER size_t GC_mark_stack_size = 0; + +#ifdef PARALLEL_MARK + GC_INNER mse * volatile GC_mark_stack_top = NULL; + /* Updated only with mark lock held, but read asynchronously. */ + STATIC volatile AO_t GC_first_nonempty = 0; + /* Lowest entry on mark stack */ + /* that may be nonempty. */ + /* Updated only by initiating */ + /* thread. */ +#else + GC_INNER mse * GC_mark_stack_top = NULL; +#endif + +GC_INNER mark_state_t GC_mark_state = MS_NONE; + +GC_INNER GC_bool GC_mark_stack_too_small = FALSE; + +static struct hblk * scan_ptr; + +STATIC 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_INNER GC_bool GC_collection_in_progress(void) +{ + return(GC_mark_state != MS_NONE); +} + +/* clear all mark bits in the header */ +GC_INNER void GC_clear_hdr_marks(hdr *hhdr) +{ + size_t last_bit = FINAL_MARK_BIT(hhdr -> hb_sz); + BZERO(hhdr -> hb_marks, sizeof(hhdr->hb_marks)); + set_mark_bit_from_hdr(hhdr, last_bit); + hhdr -> hb_n_marks = 0; +} + +/* Set all mark bits in the header. Used for uncollectable blocks. */ +GC_INNER 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.) + */ +GC_INNER 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 + void GC_check_dirty(void); +#endif + +/* Initiate a garbage collection. Initiates a full collection if the */ +/* mark state is invalid. */ +GC_INNER void GC_initiate_gc(void) +{ +# ifndef GC_DISABLE_INCREMENTAL + if (GC_dirty_maintained) GC_read_dirty(); +# endif +# 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 */ + +#ifdef GC_DISABLE_INCREMENTAL +# define GC_push_next_marked_dirty(h) GC_push_next_marked(h) +#else + STATIC struct hblk * GC_push_next_marked_dirty(struct hblk *h); + /* Invoke GC_push_marked on next dirty block above h. */ + /* Return a pointer just past the end of this block. */ +#endif /* !GC_DISABLE_INCREMENTAL */ +STATIC struct hblk * GC_push_next_marked(struct hblk *h); + /* Ditto, but also mark from clean pages. */ +STATIC struct hblk * GC_push_next_marked_uncollectable(struct hblk *h); + /* Ditto, but mark only from uncollectable pages. */ + +static void alloc_mark_stack(size_t); + +# if (defined(MSWIN32) || defined(MSWINCE)) && !defined(__GNUC__) \ + || defined(MSWIN32) && defined(I386) /* for Win98 */ \ + || 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. */ + /* FIXME: Should we really need it for WinCE? If yes then */ + /* WRAP_MARK_SOME should be also defined for CeGCC which requires */ + /* CPU/OS-specific code in mark_ex_handler() and GC_mark_some() */ + /* (for manual stack unwinding and exception handler installation). */ +# 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_INNER 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); + } +} + +#ifdef WRAP_MARK_SOME + +# if (defined(MSWIN32) || defined(MSWINCE)) && defined(__GNUC__) + + 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 */ + +#if defined(GC_WIN32_THREADS) && !defined(__GNUC__) + GC_bool GC_started_thread_while_stopped(void); + /* In win32_threads.c. Did we invalidate mark phase with an */ + /* unexpected thread start? */ +#endif + + GC_INNER GC_bool GC_mark_some(ptr_t cold_gc_frame) + { + GC_bool ret_val; + +# if defined(MSWIN32) || defined(MSWINCE) +# 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. */ + /* This code seems to be necessary for WinCE (at least in */ + /* the case we'd decide to add MEM_PRIVATE sections to */ + /* data roots in GC_register_dynamic_libraries()). */ + /* 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_INNER GC_bool GC_mark_stack_empty(void) +{ + return(GC_mark_stack_top < GC_mark_stack); +} + +GC_INNER void GC_invalidate_mark_state(void) +{ + GC_mark_state = MS_INVALID; + GC_mark_stack_top = GC_mark_stack-1; +} + +GC_INNER 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. + */ +GC_INNER 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. */ + +GC_INNER 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 ((word)(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 + +GC_INNER 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. */ +GC_INNER 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 = FALSE; + GC_bool recycle_old = (!GC_incremental || GC_incremental_at_stack_alloc); + + GC_incremental_at_stack_alloc = GC_incremental; +# else +# define recycle_old TRUE +# 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; +} + +GC_INNER 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 (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; +} + +#ifndef GC_DISABLE_INCREMENTAL + + /* Analogous to the above, but push only those pages h with */ + /* dirty_fn(h) != 0. We use GC_push_all 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 GC_push_all pushes a small fixed */ + /* number of entries. (This is invoked only if GC_push_all pushes */ + /* a single entry, or if it marks each object before pushing it, thus */ + /* ensuring progress in the event of a stack overflow.) */ + STATIC void GC_push_selected(ptr_t bottom, ptr_t top, + GC_bool (*dirty_fn)(struct hblk *)) + { + struct hblk * h; + + bottom = (ptr_t)(((word) bottom + ALIGNMENT-1) & ~(ALIGNMENT-1)); + top = (ptr_t)(((word) top) & ~(ALIGNMENT-1)); + if (bottom >= top) return; + + h = HBLKPTR(bottom + HBLKSIZE); + if (top <= (ptr_t) h) { + if ((*dirty_fn)(h-1)) { + GC_push_all(bottom, top); + } + return; + } + if ((*dirty_fn)(h-1)) { + GC_push_all(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 */ + GC_push_all((ptr_t)h, top); + return; + } else { + GC_push_all((ptr_t)h, (ptr_t)(h+1)); + } + } + h++; + } + + if ((ptr_t)h != top && (*dirty_fn)(h)) { + GC_push_all((ptr_t)h, top); + } + if (GC_mark_stack_top >= GC_mark_stack_limit) { + ABORT("Unexpected mark stack overflow"); + } + } + + void GC_push_conditional(ptr_t bottom, ptr_t top, GC_bool all) + { + if (!all) { + GC_push_selected(bottom, top, GC_page_was_dirty); + } else { +# ifdef PROC_VDB + if (GC_dirty_maintained) { + /* Pages that were never dirtied cannot contain pointers. */ + GC_push_selected(bottom, top, GC_page_was_ever_dirty); + } else +# endif + /* else */ { + GC_push_all(bottom, top); + } + } + } +#endif /* !GC_DISABLE_INCREMENTAL */ + +#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*/ +GC_API struct GC_ms_entry * GC_CALL 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), FALSE)) { + 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; +} + +#if defined(MANUAL_VDB) && defined(THREADS) + void GC_dirty(ptr_t p); +#endif + +/* 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) + GC_INNER void GC_mark_and_push_stack(ptr_t p, ptr_t source) +# else + GC_INNER 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), FALSE)) { + 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. */ +} +# undef source + +# 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; + DCL_LOCK_STATE; + + 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. + */ +GC_INNER 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 +} + +GC_INNER 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 /* !USE_MARK_BYTES && MARK_BIT_PER_GRANULE */ + +#ifdef USE_PUSH_MARKED_ACCELERATORS +/* Push all objects reachable from marked objects in the given block */ +/* containing objects of size 1 granule. */ +STATIC 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_PTRS + +/* Push all objects reachable from marked objects in the given block */ +/* of size 2 (granules) objects. */ +STATIC 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. */ +STATIC 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_PTRS */ + +#endif /* USE_PUSH_MARKED_ACCELERATORS */ + +/* Push all objects reachable from marked objects in the given block */ +STATIC 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_PTRS) + 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 GC_DISABLE_INCREMENTAL + /* 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 /* GC_DISABLE_INCREMENTAL */ + +/* Similar to GC_push_marked, but skip over unallocated blocks */ +/* and return address of next plausible block. */ +STATIC 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 GC_DISABLE_INCREMENTAL + /* Identical to above, but mark only from dirty pages */ + STATIC 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 /* !GC_DISABLE_INCREMENTAL */ + +/* Similar to above, but for uncollectable pages. Needed since we */ +/* do not clear marks for such pages, even for full collections. */ +STATIC 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)); +}