root/gc/include/private/gc_pmark.h

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INCLUDED FROM


DEFINITIONS

This source file includes following definitions.
  1. mse

   1 /*
   2  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   3  * Copyright (c) 2001 by Hewlett-Packard Company. All rights reserved.
   4  *
   5  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   6  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   7  *
   8  * Permission is hereby granted to use or copy this program
   9  * for any purpose,  provided the above notices are retained on all copies.
  10  * Permission to modify the code and to distribute modified code is granted,
  11  * provided the above notices are retained, and a notice that the code was
  12  * modified is included with the above copyright notice.
  13  *
  14  */
  15 
  16 /* Private declarations of GC marker data structures and macros */
  17 
  18 /*
  19  * Declarations of mark stack.  Needed by marker and client supplied mark
  20  * routines.  Transitively include gc_priv.h.
  21  * (Note that gc_priv.h should not be included before this, since this
  22  * includes dbg_mlc.h, which wants to include gc_priv.h AFTER defining
  23  * I_HIDE_POINTERS.)
  24  */
  25 #ifndef GC_PMARK_H
  26 # define GC_PMARK_H
  27 
  28 # if defined(KEEP_BACK_PTRS) || defined(PRINT_BLACK_LIST)
  29 #   include "dbg_mlc.h"
  30 # endif
  31 # ifndef GC_MARK_H
  32 #   include "../gc_mark.h"
  33 # endif
  34 # ifndef GC_PRIVATE_H
  35 #   include "gc_priv.h"
  36 # endif
  37 
  38 /* The real declarations of the following is in gc_priv.h, so that      */
  39 /* we can avoid scanning the following table.                           */
  40 /*
  41 extern mark_proc GC_mark_procs[MAX_MARK_PROCS];
  42 */
  43 
  44 /*
  45  * Mark descriptor stuff that should remain private for now, mostly
  46  * because it's hard to export WORDSZ without including gcconfig.h.
  47  */
  48 # define BITMAP_BITS (WORDSZ - GC_DS_TAG_BITS)
  49 # define PROC(descr) \
  50         (GC_mark_procs[((descr) >> GC_DS_TAG_BITS) & (GC_MAX_MARK_PROCS-1)])
  51 # define ENV(descr) \
  52         ((descr) >> (GC_DS_TAG_BITS + GC_LOG_MAX_MARK_PROCS))
  53 # define MAX_ENV \
  54         (((word)1 << (WORDSZ - GC_DS_TAG_BITS - GC_LOG_MAX_MARK_PROCS)) - 1)
  55 
  56 
  57 extern word GC_n_mark_procs;
  58 
  59 /* Number of mark stack entries to discard on overflow. */
  60 #define GC_MARK_STACK_DISCARDS (INITIAL_MARK_STACK_SIZE/8)
  61 
  62 typedef struct GC_ms_entry {
  63     GC_word * mse_start;   /* First word of object */
  64     GC_word mse_descr;  /* Descriptor; low order two bits are tags,     */
  65                         /* identifying the upper 30 bits as one of the  */
  66                         /* following:                                   */
  67 } mse;
  68 
  69 extern word GC_mark_stack_size;
  70 
  71 extern mse * GC_mark_stack_limit;
  72 
  73 #ifdef PARALLEL_MARK
  74   extern mse * VOLATILE GC_mark_stack_top;
  75 #else
  76   extern mse * GC_mark_stack_top;
  77 #endif
  78 
  79 extern mse * GC_mark_stack;
  80 
  81 #ifdef PARALLEL_MARK
  82     /*
  83      * Allow multiple threads to participate in the marking process.
  84      * This works roughly as follows:
  85      *  The main mark stack never shrinks, but it can grow.
  86      *
  87      *  The initiating threads holds the GC lock, and sets GC_help_wanted.
  88      *  
  89      *  Other threads:
  90      *     1) update helper_count (while holding mark_lock.)
  91      *     2) allocate a local mark stack
  92      *     repeatedly:
  93      *          3) Steal a global mark stack entry by atomically replacing
  94      *             its descriptor with 0.
  95      *          4) Copy it to the local stack.
  96      *          5) Mark on the local stack until it is empty, or
  97      *             it may be profitable to copy it back.
  98      *          6) If necessary, copy local stack to global one,
  99      *             holding mark lock.
 100      *    7) Stop when the global mark stack is empty.
 101      *    8) decrement helper_count (holding mark_lock).
 102      *
 103      * This is an experiment to see if we can do something along the lines
 104      * of the University of Tokyo SGC in a less intrusive, though probably
 105      * also less performant, way.
 106      */
 107     void GC_do_parallel_mark();
 108                 /* inititate parallel marking.  */
 109 
 110     extern GC_bool GC_help_wanted;      /* Protected by mark lock       */
 111     extern unsigned GC_helper_count;    /* Number of running helpers.   */
 112                                         /* Protected by mark lock       */
 113     extern unsigned GC_active_count;    /* Number of active helpers.    */
 114                                         /* Protected by mark lock       */
 115                                         /* May increase and decrease    */
 116                                         /* within each mark cycle.  But */
 117                                         /* once it returns to 0, it     */
 118                                         /* stays zero for the cycle.    */
 119     /* GC_mark_stack_top is also protected by mark lock.        */
 120     extern mse * VOLATILE GC_first_nonempty;
 121                                         /* Lowest entry on mark stack   */
 122                                         /* that may be nonempty.        */
 123                                         /* Updated only by initiating   */
 124                                         /* thread.                      */
 125     /*
 126      * GC_notify_all_marker() is used when GC_help_wanted is first set,
 127      * when the last helper becomes inactive,
 128      * when something is added to the global mark stack, and just after
 129      * GC_mark_no is incremented.
 130      * This could be split into multiple CVs (and probably should be to
 131      * scale to really large numbers of processors.)
 132      */
 133 #endif /* PARALLEL_MARK */
 134 
 135 /* Return a pointer to within 1st page of object.       */
 136 /* Set *new_hdr_p to corr. hdr.                         */
 137 #ifdef __STDC__
 138   ptr_t GC_find_start(ptr_t current, hdr *hhdr, hdr **new_hdr_p);
 139 #else
 140   ptr_t GC_find_start();
 141 #endif
 142 
 143 mse * GC_signal_mark_stack_overflow GC_PROTO((mse *msp));
 144 
 145 # ifdef GATHERSTATS
 146 #   define ADD_TO_ATOMIC(sz) GC_atomic_in_use += (sz)
 147 #   define ADD_TO_COMPOSITE(sz) GC_composite_in_use += (sz)
 148 # else
 149 #   define ADD_TO_ATOMIC(sz)
 150 #   define ADD_TO_COMPOSITE(sz)
 151 # endif
 152 
 153 /* Push the object obj with corresponding heap block header hhdr onto   */
 154 /* the mark stack.                                                      */
 155 # define PUSH_OBJ(obj, hhdr, mark_stack_top, mark_stack_limit) \
 156 { \
 157     register word _descr = (hhdr) -> hb_descr; \
 158         \
 159     if (_descr == 0) { \
 160         ADD_TO_ATOMIC((hhdr) -> hb_sz); \
 161     } else { \
 162         ADD_TO_COMPOSITE((hhdr) -> hb_sz); \
 163         mark_stack_top++; \
 164         if (mark_stack_top >= mark_stack_limit) { \
 165           mark_stack_top = GC_signal_mark_stack_overflow(mark_stack_top); \
 166         } \
 167         mark_stack_top -> mse_start = (obj); \
 168         mark_stack_top -> mse_descr = _descr; \
 169     } \
 170 }
 171 
 172 /* Push the contents of current onto the mark stack if it is a valid    */
 173 /* ptr to a currently unmarked object.  Mark it.                        */
 174 /* If we assumed a standard-conforming compiler, we could probably      */
 175 /* generate the exit_label transparently.                               */
 176 # define PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
 177                        source, exit_label) \
 178 { \
 179     hdr * my_hhdr; \
 180     ptr_t my_current = current; \
 181  \
 182     GET_HDR(my_current, my_hhdr); \
 183     if (IS_FORWARDING_ADDR_OR_NIL(my_hhdr)) { \
 184          hdr * new_hdr = GC_invalid_header; \
 185          my_current = GC_find_start(my_current, my_hhdr, &new_hdr); \
 186          my_hhdr = new_hdr; \
 187     } \
 188     PUSH_CONTENTS_HDR(my_current, mark_stack_top, mark_stack_limit, \
 189                   source, exit_label, my_hhdr); \
 190 exit_label: ; \
 191 }
 192 
 193 /* As above, but use header cache for header lookup.    */
 194 # define HC_PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
 195                        source, exit_label) \
 196 { \
 197     hdr * my_hhdr; \
 198     ptr_t my_current = current; \
 199  \
 200     HC_GET_HDR(my_current, my_hhdr, source); \
 201     PUSH_CONTENTS_HDR(my_current, mark_stack_top, mark_stack_limit, \
 202                   source, exit_label, my_hhdr); \
 203 exit_label: ; \
 204 }
 205 
 206 /* Set mark bit, exit if it was already set.    */
 207 
 208 # ifdef USE_MARK_BYTES
 209     /* Unlike the mark bit case, there is a race here, and we may set   */
 210     /* the bit twice in the concurrent case.  This can result in the    */
 211     /* object being pushed twice.  But that's only a performance issue. */
 212 #   define SET_MARK_BIT_EXIT_IF_SET(hhdr,displ,exit_label) \
 213     { \
 214         register VOLATILE char * mark_byte_addr = \
 215                                 hhdr -> hb_marks + ((displ) >> 1); \
 216         register char mark_byte = *mark_byte_addr; \
 217           \
 218         if (mark_byte) goto exit_label; \
 219         *mark_byte_addr = 1;  \
 220     } 
 221 # else
 222 #   define SET_MARK_BIT_EXIT_IF_SET(hhdr,displ,exit_label) \
 223     { \
 224         register word * mark_word_addr = hhdr -> hb_marks + divWORDSZ(displ); \
 225           \
 226         OR_WORD_EXIT_IF_SET(mark_word_addr, (word)1 << modWORDSZ(displ), \
 227                             exit_label); \
 228     } 
 229 # endif /* USE_MARK_BYTES */
 230 
 231 /* If the mark bit corresponding to current is not set, set it, and     */
 232 /* push the contents of the object on the mark stack.  For a small      */
 233 /* object we assume that current is the (possibly interior) pointer     */
 234 /* to the object.  For large objects we assume that current points      */
 235 /* to somewhere inside the first page of the object.  If                */
 236 /* GC_all_interior_pointers is set, it may have been previously         */
 237 /* adjusted to make that true.                                          */
 238 # define PUSH_CONTENTS_HDR(current, mark_stack_top, mark_stack_limit, \
 239                            source, exit_label, hhdr) \
 240 { \
 241     int displ;  /* Displacement in block; first bytes, then words */ \
 242     int map_entry; \
 243     \
 244     displ = HBLKDISPL(current); \
 245     map_entry = MAP_ENTRY((hhdr -> hb_map), displ); \
 246     displ = BYTES_TO_WORDS(displ); \
 247     if (map_entry > CPP_MAX_OFFSET) { \
 248         if (map_entry == OFFSET_TOO_BIG) { \
 249           map_entry = displ % (hhdr -> hb_sz); \
 250           displ -= map_entry; \
 251           if (displ + (hhdr -> hb_sz) > BYTES_TO_WORDS(HBLKSIZE)) { \
 252             GC_ADD_TO_BLACK_LIST_NORMAL((word)current, source); \
 253             goto exit_label; \
 254           } \
 255         } else { \
 256           GC_ADD_TO_BLACK_LIST_NORMAL((word)current, source); goto exit_label; \
 257         } \
 258     } else { \
 259         displ -= map_entry; \
 260     } \
 261     GC_ASSERT(displ >= 0 && displ < MARK_BITS_PER_HBLK); \
 262     SET_MARK_BIT_EXIT_IF_SET(hhdr, displ, exit_label); \
 263     GC_STORE_BACK_PTR((ptr_t)source, (ptr_t)HBLKPTR(current) \
 264                                       + WORDS_TO_BYTES(displ)); \
 265     PUSH_OBJ(((word *)(HBLKPTR(current)) + displ), hhdr, \
 266              mark_stack_top, mark_stack_limit) \
 267 }
 268 
 269 #if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
 270 #   define PUSH_ONE_CHECKED_STACK(p, source) \
 271         GC_mark_and_push_stack(p, (ptr_t)(source))
 272 #else
 273 #   define PUSH_ONE_CHECKED_STACK(p, source) \
 274         GC_mark_and_push_stack(p)
 275 #endif
 276 
 277 /*
 278  * Push a single value onto mark stack. Mark from the object pointed to by p.
 279  * Invoke FIXUP_POINTER(p) before any further processing.
 280  * P is considered valid even if it is an interior pointer.
 281  * Previously marked objects are not pushed.  Hence we make progress even
 282  * if the mark stack overflows.
 283  */
 284 
 285 # if NEED_FIXUP_POINTER
 286     /* Try both the raw version and the fixed up one.   */
 287 #   define GC_PUSH_ONE_STACK(p, source) \
 288       if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr     \
 289          && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) {      \
 290          PUSH_ONE_CHECKED_STACK(p, source);     \
 291       } \
 292       FIXUP_POINTER(p); \
 293       if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr     \
 294          && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) {      \
 295          PUSH_ONE_CHECKED_STACK(p, source);     \
 296       }
 297 # else /* !NEED_FIXUP_POINTER */
 298 #   define GC_PUSH_ONE_STACK(p, source) \
 299       if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr     \
 300          && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) {      \
 301          PUSH_ONE_CHECKED_STACK(p, source);     \
 302       }
 303 # endif
 304 
 305 
 306 /*
 307  * As above, but interior pointer recognition as for
 308  * normal for heap pointers.
 309  */
 310 # define GC_PUSH_ONE_HEAP(p,source) \
 311     FIXUP_POINTER(p); \
 312     if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr       \
 313          && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) {      \
 314             GC_mark_stack_top = GC_mark_and_push( \
 315                             (GC_PTR)(p), GC_mark_stack_top, \
 316                             GC_mark_stack_limit, (GC_PTR *)(source)); \
 317     }
 318 
 319 /* Mark starting at mark stack entry top (incl.) down to        */
 320 /* mark stack entry bottom (incl.).  Stop after performing      */
 321 /* about one page worth of work.  Return the new mark stack     */
 322 /* top entry.                                                   */
 323 mse * GC_mark_from GC_PROTO((mse * top, mse * bottom, mse *limit));
 324 
 325 #define MARK_FROM_MARK_STACK() \
 326         GC_mark_stack_top = GC_mark_from(GC_mark_stack_top, \
 327                                          GC_mark_stack, \
 328                                          GC_mark_stack + GC_mark_stack_size);
 329 
 330 /*
 331  * Mark from one finalizable object using the specified
 332  * mark proc. May not mark the object pointed to by 
 333  * real_ptr. That is the job of the caller, if appropriate
 334  */
 335 # define GC_MARK_FO(real_ptr, mark_proc) \
 336 { \
 337     (*(mark_proc))(real_ptr); \
 338     while (!GC_mark_stack_empty()) MARK_FROM_MARK_STACK(); \
 339     if (GC_mark_state != MS_NONE) { \
 340         GC_set_mark_bit(real_ptr); \
 341         while (!GC_mark_some((ptr_t)0)) {} \
 342     } \
 343 }
 344 
 345 extern GC_bool GC_mark_stack_too_small;
 346                                 /* We need a larger mark stack.  May be */
 347                                 /* set by client supplied mark routines.*/
 348 
 349 typedef int mark_state_t;       /* Current state of marking, as follows:*/
 350                                 /* Used to remember where we are during */
 351                                 /* concurrent marking.                  */
 352 
 353                                 /* We say something is dirty if it was  */
 354                                 /* written since the last time we       */
 355                                 /* retrieved dirty bits.  We say it's   */
 356                                 /* grungy if it was marked dirty in the */
 357                                 /* last set of bits we retrieved.       */
 358                                 
 359                                 /* Invariant I: all roots and marked    */
 360                                 /* objects p are either dirty, or point */
 361                                 /* to objects q that are either marked  */
 362                                 /* or a pointer to q appears in a range */
 363                                 /* on the mark stack.                   */
 364 
 365 # define MS_NONE 0              /* No marking in progress. I holds.     */
 366                                 /* Mark stack is empty.                 */
 367 
 368 # define MS_PUSH_RESCUERS 1     /* Rescuing objects are currently       */
 369                                 /* being pushed.  I holds, except       */
 370                                 /* that grungy roots may point to       */
 371                                 /* unmarked objects, as may marked      */
 372                                 /* grungy objects above scan_ptr.       */
 373 
 374 # define MS_PUSH_UNCOLLECTABLE 2
 375                                 /* I holds, except that marked          */
 376                                 /* uncollectable objects above scan_ptr */
 377                                 /* may point to unmarked objects.       */
 378                                 /* Roots may point to unmarked objects  */
 379 
 380 # define MS_ROOTS_PUSHED 3      /* I holds, mark stack may be nonempty  */
 381 
 382 # define MS_PARTIALLY_INVALID 4 /* I may not hold, e.g. because of M.S. */
 383                                 /* overflow.  However marked heap       */
 384                                 /* objects below scan_ptr point to      */
 385                                 /* marked or stacked objects.           */
 386 
 387 # define MS_INVALID 5           /* I may not hold.                      */
 388 
 389 extern mark_state_t GC_mark_state;
 390 
 391 #endif  /* GC_PMARK_H */
 392 

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