finalize.c

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/*
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1996 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
 * Copyright (C) 2007 Free Software Foundation, Inc

 * 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.
 */
/* Boehm, February 1, 1996 1:19 pm PST */
# define I_HIDE_POINTERS
# include "private/gc_pmark.h"

# ifdef FINALIZE_ON_DEMAND
    int GC_finalize_on_demand = 1;
# else
    int GC_finalize_on_demand = 0;
# endif

# ifdef JAVA_FINALIZATION
    int GC_java_finalization = 1;
# else
    int GC_java_finalization = 0;
# endif

/* Type of mark procedure used for marking from finalizable object.	*/
/* This procedure normally does not mark the object, only its		*/
/* descendents.								*/
typedef void finalization_mark_proc(/* ptr_t finalizable_obj_ptr */); 

# define HASH3(addr,size,log_size) \
    ((((word)(addr) >> 3) ^ ((word)(addr) >> (3+(log_size)))) \
    & ((size) - 1))
#define HASH2(addr,log_size) HASH3(addr, 1 << log_size, log_size)

struct hash_chain_entry {
    word hidden_key;
    struct hash_chain_entry * next;
};

unsigned GC_finalization_failures = 0;
	/* Number of finalization requests that failed for lack of memory. */

static struct disappearing_link {
    struct hash_chain_entry prolog;
#   define dl_hidden_link prolog.hidden_key
				/* Field to be cleared.		*/
#   define dl_next(x) (struct disappearing_link *)((x) -> prolog.next)
#   define dl_set_next(x,y) (x) -> prolog.next = (struct hash_chain_entry *)(y)

    word dl_hidden_obj;		/* Pointer to object base	*/
} **dl_head = 0;

static signed_word log_dl_table_size = -1;
			/* Binary log of				*/
			/* current size of array pointed to by dl_head.	*/
			/* -1 ==> size is 0.				*/

word GC_dl_entries = 0;	/* Number of entries currently in disappearing	*/
			/* link table.					*/

static struct finalizable_object {
    struct hash_chain_entry prolog;
#   define fo_hidden_base prolog.hidden_key
				/* Pointer to object base.	*/
				/* No longer hidden once object */
				/* is on finalize_now queue.	*/
#   define fo_next(x) (struct finalizable_object *)((x) -> prolog.next)
#   define fo_set_next(x,y) (x) -> prolog.next = (struct hash_chain_entry *)(y)
    GC_finalization_proc fo_fn;	/* Finalizer.			*/
    ptr_t fo_client_data;
    word fo_object_size;	/* In bytes.			*/
    finalization_mark_proc * fo_mark_proc;	/* Mark-through procedure */
} **fo_head = 0;

struct finalizable_object * GC_finalize_now = 0;
	/* LIst of objects that should be finalized now.	*/

static signed_word log_fo_table_size = -1;

word GC_fo_entries = 0;

void GC_push_finalizer_structures(void)
{
    GC_push_all((ptr_t)(&dl_head), (ptr_t)(&dl_head) + sizeof(word));
    GC_push_all((ptr_t)(&fo_head), (ptr_t)(&fo_head) + sizeof(word));
    GC_push_all((ptr_t)(&GC_finalize_now),
		(ptr_t)(&GC_finalize_now) + sizeof(word));
}

/* Double the size of a hash table. *size_ptr is the log of its current	*/
/* size.  May be a noop.						*/
/* *table is a pointer to an array of hash headers.  If we succeed, we	*/
/* update both *table and *log_size_ptr.				*/
/* Lock is held.  Signals are disabled.					*/
void GC_grow_table(struct hash_chain_entry ***table,
		   signed_word *log_size_ptr)
{
    register word i;
    register struct hash_chain_entry *p;
    signed_word log_old_size = *log_size_ptr;
    signed_word log_new_size = log_old_size + 1;
    word old_size = ((log_old_size == -1)? 0: (1 << log_old_size));
    word new_size = (word)1 << log_new_size;
    /* FIXME: Power of 2 size often gets rounded up to one more page. */
    struct hash_chain_entry **new_table = (struct hash_chain_entry **)
    	GC_INTERNAL_MALLOC_IGNORE_OFF_PAGE(
    		(size_t)new_size * sizeof(struct hash_chain_entry *), NORMAL);
    
    if (new_table == 0) {
    	if (table == 0) {
    	    ABORT("Insufficient space for initial table allocation");
    	} else {
    	    return;
    	}
    }
    for (i = 0; i < old_size; i++) {
      p = (*table)[i];
      while (p != 0) {
        ptr_t real_key = (ptr_t)REVEAL_POINTER(p -> hidden_key);
        struct hash_chain_entry *next = p -> next;
        size_t new_hash = HASH3(real_key, new_size, log_new_size);
        
        p -> next = new_table[new_hash];
        new_table[new_hash] = p;
        p = next;
      }
    }
    *log_size_ptr = log_new_size;
    *table = new_table;
}

int GC_register_disappearing_link(void * * link)
{
    ptr_t base;
    
    base = (ptr_t)GC_base((void *)link);
    if (base == 0)
    	ABORT("Bad arg to GC_register_disappearing_link");
    return(GC_general_register_disappearing_link(link, base));
}

int GC_general_register_disappearing_link(void * * link, void * obj)
{
    struct disappearing_link *curr_dl;
    size_t index;
    struct disappearing_link * new_dl;
    DCL_LOCK_STATE;
    
    if ((word)link & (ALIGNMENT-1))
    	ABORT("Bad arg to GC_general_register_disappearing_link");
#   ifdef THREADS
    	LOCK();
#   endif
    if (log_dl_table_size == -1
        || GC_dl_entries > ((word)1 << log_dl_table_size)) {
    	GC_grow_table((struct hash_chain_entry ***)(&dl_head),
    		      &log_dl_table_size);
	if (GC_print_stats) {
	    GC_log_printf("Grew dl table to %u entries\n",
	    	      (1 << log_dl_table_size));
	}
    }
    index = HASH2(link, log_dl_table_size);
    curr_dl = dl_head[index];
    for (curr_dl = dl_head[index]; curr_dl != 0; curr_dl = dl_next(curr_dl)) {
        if (curr_dl -> dl_hidden_link == HIDE_POINTER(link)) {
            curr_dl -> dl_hidden_obj = HIDE_POINTER(obj);
#	    ifdef THREADS
                UNLOCK();
#	    endif
            return(1);
        }
    }
    new_dl = (struct disappearing_link *)
    	GC_INTERNAL_MALLOC(sizeof(struct disappearing_link),NORMAL);
    if (0 == new_dl) {
#     ifdef THREADS
	UNLOCK();
#     endif
      new_dl = (struct disappearing_link *)
	      GC_oom_fn(sizeof(struct disappearing_link));
      if (0 == new_dl) {
	GC_finalization_failures++;
	return(0);
      }
      /* It's not likely we'll make it here, but ... */
#     ifdef THREADS
	LOCK();
#     endif
    }
    new_dl -> dl_hidden_obj = HIDE_POINTER(obj);
    new_dl -> dl_hidden_link = HIDE_POINTER(link);
    dl_set_next(new_dl, dl_head[index]);
    dl_head[index] = new_dl;
    GC_dl_entries++;
#   ifdef THREADS
        UNLOCK();
#   endif
    return(0);
}

int GC_unregister_disappearing_link(void * * link)
{
    struct disappearing_link *curr_dl, *prev_dl;
    size_t index;
    DCL_LOCK_STATE;
    
    LOCK();
    index = HASH2(link, log_dl_table_size);
    if (((word)link & (ALIGNMENT-1))) goto out;
    prev_dl = 0; curr_dl = dl_head[index];
    while (curr_dl != 0) {
        if (curr_dl -> dl_hidden_link == HIDE_POINTER(link)) {
            if (prev_dl == 0) {
                dl_head[index] = dl_next(curr_dl);
            } else {
                dl_set_next(prev_dl, dl_next(curr_dl));
            }
            GC_dl_entries--;
            UNLOCK();
#	    ifdef DBG_HDRS_ALL
	      dl_set_next(curr_dl, 0);
#	    else
              GC_free((void *)curr_dl);
#	    endif
            return(1);
        }
        prev_dl = curr_dl;
        curr_dl = dl_next(curr_dl);
    }
out:
    UNLOCK();
    return(0);
}

/* Possible finalization_marker procedures.  Note that mark stack	*/
/* overflow is handled by the caller, and is not a disaster.		*/
GC_API void GC_normal_finalize_mark_proc(ptr_t p)
{
    hdr * hhdr = HDR(p);
    
    PUSH_OBJ(p, hhdr, GC_mark_stack_top,
	     &(GC_mark_stack[GC_mark_stack_size]));
}

/* This only pays very partial attention to the mark descriptor.	*/
/* It does the right thing for normal and atomic objects, and treats	*/
/* most others as normal.						*/
GC_API void GC_ignore_self_finalize_mark_proc(ptr_t p)
{
    hdr * hhdr = HDR(p);
    word descr = hhdr -> hb_descr;
    ptr_t q, r;
    ptr_t scan_limit;
    ptr_t target_limit = p + hhdr -> hb_sz - 1;
    
    if ((descr & GC_DS_TAGS) == GC_DS_LENGTH) {
       scan_limit = p + descr - sizeof(word);
    } else {
       scan_limit = target_limit + 1 - sizeof(word);
    }
    for (q = p; q <= scan_limit; q += ALIGNMENT) {
    	r = *(ptr_t *)q;
    	if (r < p || r > target_limit) {
    	    GC_PUSH_ONE_HEAP(r, q);
    	}
    }
}

/*ARGSUSED*/
GC_API void GC_null_finalize_mark_proc(ptr_t p)
{
}

/* Possible finalization_marker procedures.  Note that mark stack	*/
/* overflow is handled by the caller, and is not a disaster.		*/

/* GC_unreachable_finalize_mark_proc is an alias for normal marking,	*/
/* but it is explicitly tested for, and triggers different		*/
/* behavior.  Objects registered in this way are not finalized		*/
/* if they are reachable by other finalizable objects, eve if those	*/
/* other objects specify no ordering.					*/
GC_API void GC_unreachable_finalize_mark_proc(ptr_t p)
{
    GC_normal_finalize_mark_proc(p);
}



/* Register a finalization function.  See gc.h for details.	*/
/* in the nonthreads case, we try to avoid disabling signals,	*/
/* since it can be expensive.  Threads packages typically	*/
/* make it cheaper.						*/
/* The last parameter is a procedure that determines		*/
/* marking for finalization ordering.  Any objects marked	*/
/* by that procedure will be guaranteed to not have been	*/
/* finalized when this finalizer is invoked.			*/
GC_API void GC_register_finalizer_inner(void * obj,
					GC_finalization_proc fn, void *cd,
					GC_finalization_proc *ofn, void **ocd,
					finalization_mark_proc mp)
{
    ptr_t base;
    struct finalizable_object * curr_fo, * prev_fo;
    size_t index;
    struct finalizable_object *new_fo;
    hdr *hhdr;
    DCL_LOCK_STATE;

#   ifdef THREADS
	LOCK();
#   endif
    if (log_fo_table_size == -1
        || GC_fo_entries > ((word)1 << log_fo_table_size)) {
    	GC_grow_table((struct hash_chain_entry ***)(&fo_head),
    		      &log_fo_table_size);
	if (GC_print_stats) {
	    GC_log_printf("Grew fo table to %u entries\n",
	    	          (1 << log_fo_table_size));
	}
    }
    /* in the THREADS case signals are disabled and we hold allocation	*/
    /* lock; otherwise neither is true.  Proceed carefully.		*/
    base = (ptr_t)obj;
    index = HASH2(base, log_fo_table_size);
    prev_fo = 0; curr_fo = fo_head[index];
    while (curr_fo != 0) {
        GC_ASSERT(GC_size(curr_fo) >= sizeof(struct finalizable_object));
        if (curr_fo -> fo_hidden_base == HIDE_POINTER(base)) {
            /* Interruption by a signal in the middle of this	*/
            /* should be safe.  The client may see only *ocd	*/
            /* updated, but we'll declare that to be his	*/
            /* problem.						*/
            if (ocd) *ocd = (void *) (curr_fo -> fo_client_data);
            if (ofn) *ofn = curr_fo -> fo_fn;
            /* Delete the structure for base. */
                if (prev_fo == 0) {
                  fo_head[index] = fo_next(curr_fo);
                } else {
                  fo_set_next(prev_fo, fo_next(curr_fo));
                }
            if (fn == 0) {
                GC_fo_entries--;
                  /* May not happen if we get a signal.  But a high	*/
                  /* estimate will only make the table larger than	*/
                  /* necessary.						*/
#		if !defined(THREADS) && !defined(DBG_HDRS_ALL)
                  GC_free((void *)curr_fo);
#		endif
            } else {
                curr_fo -> fo_fn = fn;
                curr_fo -> fo_client_data = (ptr_t)cd;
                curr_fo -> fo_mark_proc = mp;
		/* Reinsert it.  We deleted it first to maintain	*/
		/* consistency in the event of a signal.		*/
		if (prev_fo == 0) {
                  fo_head[index] = curr_fo;
                } else {
                  fo_set_next(prev_fo, curr_fo);
                }
            }
#	    ifdef THREADS
                UNLOCK();
#	    endif
            return;
        }
        prev_fo = curr_fo;
        curr_fo = fo_next(curr_fo);
    }
    if (ofn) *ofn = 0;
    if (ocd) *ocd = 0;
    if (fn == 0) {
#	ifdef THREADS
            UNLOCK();
#	endif
        return;
    }
    GET_HDR(base, hhdr);
    if (0 == hhdr) {
      /* We won't collect it, hence finalizer wouldn't be run. */
#     ifdef THREADS
          UNLOCK();
#     endif
      return;
    }
    new_fo = (struct finalizable_object *)
    	GC_INTERNAL_MALLOC(sizeof(struct finalizable_object),NORMAL);
    GC_ASSERT(GC_size(new_fo) >= sizeof(struct finalizable_object));
    if (EXPECT(0 == new_fo, FALSE)) {
#     ifdef THREADS
	UNLOCK();
#     endif
      new_fo = (struct finalizable_object *)
	      GC_oom_fn(sizeof(struct finalizable_object));
      if (0 == new_fo) {
	GC_finalization_failures++;
	return;
      }
      /* It's not likely we'll make it here, but ... */
#     ifdef THREADS
	LOCK();
#     endif
    }
    new_fo -> fo_hidden_base = (word)HIDE_POINTER(base);
    new_fo -> fo_fn = fn;
    new_fo -> fo_client_data = (ptr_t)cd;
    new_fo -> fo_object_size = hhdr -> hb_sz;
    new_fo -> fo_mark_proc = mp;
    fo_set_next(new_fo, fo_head[index]);
    GC_fo_entries++;
    fo_head[index] = new_fo;
#   ifdef THREADS
        UNLOCK();
#   endif
}

void GC_register_finalizer(void * obj,
			       GC_finalization_proc fn, void * cd,
			       GC_finalization_proc *ofn, void ** ocd)
{
    GC_register_finalizer_inner(obj, fn, cd, ofn,
    				ocd, GC_normal_finalize_mark_proc);
}

void GC_register_finalizer_ignore_self(void * obj,
			       GC_finalization_proc fn, void * cd,
			       GC_finalization_proc *ofn, void ** ocd)
{