mark_rts.c

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/* 
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1994 by Xerox Corporation.  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 <stdio.h>
# include "private/gc_priv.h"

/* Data structure for list of root sets.				*/
/* We keep a hash table, so that we can filter out duplicate additions.	*/
/* Under Win32, we need to do a better job of filtering overlaps, so	*/
/* we resort to sequential search, and pay the price.			*/
/* This is really declared in gc_priv.h:
struct roots {
	ptr_t r_start;
	ptr_t r_end;
 #	if !defined(MSWIN32) && !defined(MSWINCE)
	  struct roots * r_next;
 #	endif
	GC_bool r_tmp;
	  	-- Delete before registering new dynamic libraries
};

struct roots GC_static_roots[MAX_ROOT_SETS];
*/

int GC_no_dls = 0;	/* Register dynamic library data segments.	*/

static int n_root_sets = 0;

	/* GC_static_roots[0..n_root_sets) contains the valid root sets. */

# if !defined(NO_DEBUGGING)
/* For debugging:	*/
void GC_print_static_roots()
{
    register int i;
    size_t total = 0;
    
    for (i = 0; i < n_root_sets; i++) {
        GC_printf2("From 0x%lx to 0x%lx ",
        	   (unsigned long) GC_static_roots[i].r_start,
        	   (unsigned long) GC_static_roots[i].r_end);
        if (GC_static_roots[i].r_tmp) {
            GC_printf0(" (temporary)\n");
        } else {
            GC_printf0("\n");
        }
        total += GC_static_roots[i].r_end - GC_static_roots[i].r_start;
    }
    GC_printf1("Total size: %ld\n", (unsigned long) total);
    if (GC_root_size != total) {
     	GC_printf1("GC_root_size incorrect: %ld!!\n",
     		   (unsigned long) GC_root_size);
    }
}
# endif /* NO_DEBUGGING */

/* Primarily for debugging support:	*/
/* Is the address p in one of the registered static			*/
/* root sections?							*/
GC_bool GC_is_static_root(p)
ptr_t p;
{
    static int last_root_set = MAX_ROOT_SETS;
    register int i;
    
    
    if (last_root_set < n_root_sets
	&& p >= GC_static_roots[last_root_set].r_start
        && p < GC_static_roots[last_root_set].r_end) return(TRUE);
    for (i = 0; i < n_root_sets; i++) {
    	if (p >= GC_static_roots[i].r_start
            && p < GC_static_roots[i].r_end) {
            last_root_set = i;
            return(TRUE);
        }
    }
    return(FALSE);
}

#if !defined(MSWIN32) && !defined(MSWINCE)
/* 
#   define LOG_RT_SIZE 6
#   define RT_SIZE (1 << LOG_RT_SIZE)  -- Power of 2, may be != MAX_ROOT_SETS

    struct roots * GC_root_index[RT_SIZE];
	-- Hash table header.  Used only to check whether a range is
	-- already present.
	-- really defined in gc_priv.h
*/

static int rt_hash(addr)
char * addr;
{
    word result = (word) addr;
#   if CPP_WORDSZ > 8*LOG_RT_SIZE
	result ^= result >> 8*LOG_RT_SIZE;
#   endif
#   if CPP_WORDSZ > 4*LOG_RT_SIZE
	result ^= result >> 4*LOG_RT_SIZE;
#   endif
    result ^= result >> 2*LOG_RT_SIZE;
    result ^= result >> LOG_RT_SIZE;
    result &= (RT_SIZE-1);
    return(result);
}

/* Is a range starting at b already in the table? If so return a	*/
/* pointer to it, else NIL.						*/
struct roots * GC_roots_present(b)
char *b;
{
    register int h = rt_hash(b);
    register struct roots *p = GC_root_index[h];
    
    while (p != 0) {
        if (p -> r_start == (ptr_t)b) return(p);
        p = p -> r_next;
    }
    return(FALSE);
}

/* Add the given root structure to the index. */
static void add_roots_to_index(p)
struct roots *p;
{
    register int h = rt_hash(p -> r_start);
    
    p -> r_next = GC_root_index[h];
    GC_root_index[h] = p;
}

# else /* MSWIN32 || MSWINCE */

#   define add_roots_to_index(p)

# endif




word GC_root_size = 0;

void GC_add_roots(b, e)
char * b; char * e;
{
    DCL_LOCK_STATE;
    
    DISABLE_SIGNALS();
    LOCK();
    GC_add_roots_inner(b, e, FALSE);
    UNLOCK();
    ENABLE_SIGNALS();
}


/* Add [b,e) to the root set.  Adding the same interval a second time	*/
/* is a moderately fast noop, and hence benign.  We do not handle	*/
/* different but overlapping intervals efficiently.  (We do handle	*/
/* them correctly.)							*/
/* Tmp specifies that the interval may be deleted before 		*/
/* reregistering dynamic libraries.					*/ 
void GC_add_roots_inner(b, e, tmp)
char * b; char * e;
GC_bool tmp;
{
    struct roots * old;
    
#   if defined(MSWIN32) || defined(MSWINCE)
      /* Spend the time to ensure that there are no overlapping	*/
      /* or adjacent intervals.					*/
      /* This could be done faster with e.g. a			*/
      /* balanced tree.  But the execution time here is		*/
      /* virtually guaranteed to be dominated by the time it	*/
      /* takes to scan the roots.				*/
      {
        register int i;
        
        for (i = 0; i < n_root_sets; i++) {
            old = GC_static_roots + i;
            if ((ptr_t)b <= old -> r_end && (ptr_t)e >= old -> r_start) {
                if ((ptr_t)b < old -> r_start) {
                    old -> r_start = (ptr_t)b;
                    GC_root_size += (old -> r_start - (ptr_t)b);
                }
                if ((ptr_t)e > old -> r_end) {
                    old -> r_end = (ptr_t)e;
                    GC_root_size += ((ptr_t)e - old -> r_end);
                }
                old -> r_tmp &= tmp;
                break;
            }
        }
        if (i < n_root_sets) {
          /* merge other overlapping intervals */
            struct roots *other;
            
            for (i++; i < n_root_sets; i++) {
              other = GC_static_roots + i;
              b = (char *)(other -> r_start);
              e = (char *)(other -> r_end);
              if ((ptr_t)b <= old -> r_end && (ptr_t)e >= old -> r_start) {
                if ((ptr_t)b < old -> r_start) {
                    old -> r_start = (ptr_t)b;
                    GC_root_size += (old -> r_start - (ptr_t)b);
                }
                if ((ptr_t)e > old -> r_end) {
                    old -> r_end = (ptr_t)e;
                    GC_root_size += ((ptr_t)e - old -> r_end);
                }
                old -> r_tmp &= other -> r_tmp;
                /* Delete this entry. */
                  GC_root_size -= (other -> r_end - other -> r_start);
                  other -> r_start = GC_static_roots[n_root_sets-1].r_start;
                  other -> r_end = GC_static_roots[n_root_sets-1].r_end;
                                  n_root_sets--;
              }
            }
          return;
        }
      }
#   else
      old = GC_roots_present(b);
      if (old != 0) {
        if ((ptr_t)e <= old -> r_end) /* already there */ return;
        /* else extend */
        GC_root_size += (ptr_t)e - old -> r_end;
        old -> r_end = (ptr_t)e;
        return;
      }
#   endif
    if (n_root_sets == MAX_ROOT_SETS) {
        ABORT("Too many root sets\n");
    }
    GC_static_roots[n_root_sets].r_start = (ptr_t)b;
    GC_static_roots[n_root_sets].r_end = (ptr_t)e;
    GC_static_roots[n_root_sets].r_tmp = tmp;
#   if !defined(MSWIN32) && !defined(MSWINCE)
      GC_static_roots[n_root_sets].r_next = 0;
#   endif
    add_roots_to_index(GC_static_roots + n_root_sets);
    GC_root_size += (ptr_t)e - (ptr_t)b;
    n_root_sets++;
}

static GC_bool roots_were_cleared = FALSE;

void GC_clear_roots GC_PROTO((void))
{
    DCL_LOCK_STATE;
    
    DISABLE_SIGNALS();
    LOCK();
    roots_were_cleared = TRUE;
    n_root_sets = 0;
    GC_root_size = 0;
#   if !defined(MSWIN32) && !defined(MSWINCE)
    {
    	register int i;
    	
    	for (i = 0; i < RT_SIZE; i++) GC_root_index[i] = 0;
    }
#   endif
    UNLOCK();
    ENABLE_SIGNALS();
}

/* Internal use only; lock held.	*/
static void GC_remove_root_at_pos(i) 
int i;
{
    GC_root_size -= (GC_static_roots[i].r_end - GC_static_roots[i].r_start);
    GC_static_roots[i].r_start = GC_static_roots[n_root_sets-1].r_start;
    GC_static_roots[i].r_end = GC_static_roots[n_root_sets-1].r_end;
    GC_static_roots[i].r_tmp = GC_static_roots[n_root_sets-1].r_tmp;
    n_root_sets--;
}

#if !defined(MSWIN32) && !defined(MSWINCE)
static void GC_rebuild_root_index()
{
    register int i;
    	
    for (i = 0; i < RT_SIZE; i++) GC_root_index[i] = 0;
    for (i = 0; i < n_root_sets; i++)
	add_roots_to_index(GC_static_roots + i);
}
#endif

/* Internal use only; lock held.	*/
void GC_remove_tmp_roots()
{
    register int i;
    
    for (i = 0; i < n_root_sets; ) {
    	if (GC_static_roots[i].r_tmp) {
            GC_remove_root_at_pos(i);
    	} else {
    	    i++;
    }
    }
    #if !defined(MSWIN32) && !defined(MSWINCE)
    GC_rebuild_root_index();
    #endif
}

#if !defined(MSWIN32) && !defined(MSWINCE)
void GC_remove_roots(b, e)
char * b; char * e;
{
    DCL_LOCK_STATE;
    
    DISABLE_SIGNALS();
    LOCK();
    GC_remove_roots_inner(b, e);
    UNLOCK();
    ENABLE_SIGNALS();
}