boehm-gc/include/private/gc_pmark.h

   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 # ifdef PRINT_BLACK_LIST
 139     ptr_t GC_find_start(ptr_t current, hdr *hhdr, hdr **new_hdr_p,
 140                         ptr_t source);
 141 # else
 142     ptr_t GC_find_start(ptr_t current, hdr *hhdr, hdr **new_hdr_p);
 143 # endif
 144 #else
 145   ptr_t GC_find_start();
 146 #endif
 147
 148 mse *GC_signal_mark_stack_overflow(mse *msp);
 149
 150 # ifdef GATHERSTATS
 151 #   define ADD_TO_ATOMIC(sz) GC_atomic_in_use += (sz)
 152 #   define ADD_TO_COMPOSITE(sz) GC_composite_in_use += (sz)
 153 # else
 154 #   define ADD_TO_ATOMIC(sz)
 155 #   define ADD_TO_COMPOSITE(sz)
 156 # endif
 157
 158 /* Push the object obj with corresponding heap block header hhdr onto   */
 159 /* the mark stack.                                                      */
 160 # define PUSH_OBJ(obj, hhdr, mark_stack_top, mark_stack_limit) \
 161 { \
 162     register word _descr = (hhdr) -> hb_descr; \
 163         \
 164     if (_descr == 0) { \
 165         ADD_TO_ATOMIC((hhdr) -> hb_sz); \
 166     } else { \
 167         ADD_TO_COMPOSITE((hhdr) -> hb_sz); \
 168         mark_stack_top++; \
 169         if (mark_stack_top >= mark_stack_limit) { \
 170           mark_stack_top = GC_signal_mark_stack_overflow(mark_stack_top); \
 171         } \
 172         mark_stack_top -> mse_start = (obj); \
 173         mark_stack_top -> mse_descr = _descr; \
 174     } \
 175 }
 176
 177 #ifdef PRINT_BLACK_LIST
 178 #   define GC_FIND_START(current, hhdr, new_hdr_p, source) \
 179         GC_find_start(current, hhdr, new_hdr_p, source)
 180 #else
 181 #   define GC_FIND_START(current, hhdr, new_hdr_p, source) \
 182         GC_find_start(current, hhdr, new_hdr_p)
 183 #endif
 184
 185 /* Push the contents of current onto the mark stack if it is a valid    */
 186 /* ptr to a currently unmarked object.  Mark it.                        */
 187 /* If we assumed a standard-conforming compiler, we could probably      */
 188 /* generate the exit_label transparently.                               */
 189 # define PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
 190                        source, exit_label) \
 191 { \
 192     hdr * my_hhdr; \
 193     ptr_t my_current = current; \
 194  \
 195     GET_HDR(my_current, my_hhdr); \
 196     if (IS_FORWARDING_ADDR_OR_NIL(my_hhdr)) { \
 197          hdr * new_hdr = GC_invalid_header; \
 198          my_current = GC_FIND_START(my_current, my_hhdr, \
 199                                     &new_hdr, (word)source); \
 200          my_hhdr = new_hdr; \
 201     } \
 202     PUSH_CONTENTS_HDR(my_current, mark_stack_top, mark_stack_limit, \
 203                   source, exit_label, my_hhdr); \
 204 exit_label: ; \
 205 }
 206
 207 /* As above, but use header cache for header lookup.    */
 208 # define HC_PUSH_CONTENTS(current, mark_stack_top, mark_stack_limit, \
 209                        source, exit_label) \
 210 { \
 211     hdr * my_hhdr; \
 212     ptr_t my_current = current; \
 213  \
 214     HC_GET_HDR(my_current, my_hhdr, source); \
 215     PUSH_CONTENTS_HDR(my_current, mark_stack_top, mark_stack_limit, \
 216                   source, exit_label, my_hhdr); \
 217 exit_label: ; \
 218 }
 219
 220 /* Set mark bit, exit if it was already set.    */
 221
 222 # ifdef USE_MARK_BYTES
 223     /* Unlike the mark bit case, there is a race here, and we may set   */
 224     /* the bit twice in the concurrent case.  This can result in the    */
 225     /* object being pushed twice.  But that's only a performance issue. */
 226 #   define SET_MARK_BIT_EXIT_IF_SET(hhdr,displ,exit_label) \
 227     { \
 228         register VOLATILE char * mark_byte_addr = \
 229                                 hhdr -> hb_marks + ((displ) >> 1); \
 230         register char mark_byte = *mark_byte_addr; \
 231           \
 232         if (mark_byte) goto exit_label; \
 233         *mark_byte_addr = 1;  \
 234     }
 235 # else
 236 #   define SET_MARK_BIT_EXIT_IF_SET(hhdr,displ,exit_label) \
 237     { \
 238         register word * mark_word_addr = hhdr -> hb_marks + divWORDSZ(displ); \
 239           \
 240         OR_WORD_EXIT_IF_SET(mark_word_addr, (word)1 << modWORDSZ(displ), \
 241                             exit_label); \
 242     }
 243 # endif /* USE_MARK_BYTES */
 244
 245 /* If the mark bit corresponding to current is not set, set it, and     */
 246 /* push the contents of the object on the mark stack.  For a small      */
 247 /* object we assume that current is the (possibly interior) pointer     */
 248 /* to the object.  For large objects we assume that current points      */
 249 /* to somewhere inside the first page of the object.  If                */
 250 /* GC_all_interior_pointers is set, it may have been previously         */
 251 /* adjusted to make that true.                                          */
 252 # define PUSH_CONTENTS_HDR(current, mark_stack_top, mark_stack_limit, \
 253                            source, exit_label, hhdr) \
 254 { \
 255     int displ;  /* Displacement in block; first bytes, then words */ \
 256     int map_entry; \
 257     \
 258     displ = HBLKDISPL(current); \
 259     map_entry = MAP_ENTRY((hhdr -> hb_map), displ); \
 260     displ = BYTES_TO_WORDS(displ); \
 261     if (map_entry > CPP_MAX_OFFSET) { \
 262         if (map_entry == OFFSET_TOO_BIG) { \
 263           map_entry = displ % (hhdr -> hb_sz); \
 264           displ -= map_entry; \
 265           if (displ + (hhdr -> hb_sz) > BYTES_TO_WORDS(HBLKSIZE)) { \
 266             GC_ADD_TO_BLACK_LIST_NORMAL((word)current, source); \
 267             goto exit_label; \
 268           } \
 269         } else { \
 270           GC_ADD_TO_BLACK_LIST_NORMAL((word)current, source); goto exit_label; \
 271         } \
 272     } else { \
 273         displ -= map_entry; \
 274     } \
 275     GC_ASSERT(displ >= 0 && displ < MARK_BITS_PER_HBLK); \
 276     SET_MARK_BIT_EXIT_IF_SET(hhdr, displ, exit_label); \
 277     GC_STORE_BACK_PTR((ptr_t)source, (ptr_t)HBLKPTR(current) \
 278                                       + WORDS_TO_BYTES(displ)); \
 279     PUSH_OBJ(((word *)(HBLKPTR(current)) + displ), hhdr, \
 280              mark_stack_top, mark_stack_limit) \
 281 }
 282
 283 #if defined(PRINT_BLACK_LIST) || defined(KEEP_BACK_PTRS)
 284 #   define PUSH_ONE_CHECKED_STACK(p, source) \
 285         GC_mark_and_push_stack(p, (ptr_t)(source))
 286 #else
 287 #   define PUSH_ONE_CHECKED_STACK(p, source) \
 288         GC_mark_and_push_stack(p)
 289 #endif
 290
 291 /*
 292  * Push a single value onto mark stack. Mark from the object pointed to by p.
 293  * P is considered valid even if it is an interior pointer.
 294  * Previously marked objects are not pushed.  Hence we make progress even
 295  * if the mark stack overflows.
 296  */
 297 # define GC_PUSH_ONE_STACK(p, source) \
 298     if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr       \
 299          && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) {      \
 300          PUSH_ONE_CHECKED_STACK(p, source);     \
 301     }
 302
 303 /*
 304  * As above, but interior pointer recognition as for
 305  * normal for heap pointers.
 306  */
 307 # define GC_PUSH_ONE_HEAP(p,source) \
 308     if ((ptr_t)(p) >= (ptr_t)GC_least_plausible_heap_addr       \
 309          && (ptr_t)(p) < (ptr_t)GC_greatest_plausible_heap_addr) {      \
 310             GC_mark_stack_top = GC_mark_and_push( \
 311                             (GC_PTR)(p), GC_mark_stack_top, \
 312                             GC_mark_stack_limit, (GC_PTR *)(source)); \
 313     }
 314
 315 /* Mark starting at mark stack entry top (incl.) down to        */
 316 /* mark stack entry bottom (incl.).  Stop after performing      */
 317 /* about one page worth of work.  Return the new mark stack     */
 318 /* top entry.                                                   */
 319 mse * GC_mark_from GC_PROTO((mse * top, mse * bottom, mse *limit));
 320
 321 #define MARK_FROM_MARK_STACK() \
 322         GC_mark_stack_top = GC_mark_from(GC_mark_stack_top, \
 323                                          GC_mark_stack, \
 324                                          GC_mark_stack + GC_mark_stack_size);
 325
 326 /*
 327  * Mark from one finalizable object using the specified
 328  * mark proc. May not mark the object pointed to by
 329  * real_ptr. That is the job of the caller, if appropriate
 330  */
 331 # define GC_MARK_FO(real_ptr, mark_proc) \
 332 { \
 333     (*(mark_proc))(real_ptr); \
 334     while (!GC_mark_stack_empty()) MARK_FROM_MARK_STACK(); \
 335     if (GC_mark_state != MS_NONE) { \
 336         GC_set_mark_bit(real_ptr); \
 337         while (!GC_mark_some((ptr_t)0)) {} \
 338     } \
 339 }
 340
 341 extern GC_bool GC_mark_stack_too_small;
 342                                 /* We need a larger mark stack.  May be */
 343                                 /* set by client supplied mark routines.*/
 344
 345 typedef int mark_state_t;       /* Current state of marking, as follows:*/
 346                                 /* Used to remember where we are during */
 347                                 /* concurrent marking.                  */
 348
 349                                 /* We say something is dirty if it was  */
 350                                 /* written since the last time we       */
 351                                 /* retrieved dirty bits.  We say it's   */
 352                                 /* grungy if it was marked dirty in the */
 353                                 /* last set of bits we retrieved.       */
 354
 355                                 /* Invariant I: all roots and marked    */
 356                                 /* objects p are either dirty, or point */
 357                                 /* to objects q that are either marked  */
 358                                 /* or a pointer to q appears in a range */
 359                                 /* on the mark stack.                   */
 360
 361 # define MS_NONE 0              /* No marking in progress. I holds.     */
 362                                 /* Mark stack is empty.                 */
 363
 364 # define MS_PUSH_RESCUERS 1     /* Rescuing objects are currently       */
 365                                 /* being pushed.  I holds, except       */
 366                                 /* that grungy roots may point to       */
 367                                 /* unmarked objects, as may marked      */
 368                                 /* grungy objects above scan_ptr.       */
 369
 370 # define MS_PUSH_UNCOLLECTABLE 2
 371                                 /* I holds, except that marked          */
 372                                 /* uncollectable objects above scan_ptr */
 373                                 /* may point to unmarked objects.       */
 374                                 /* Roots may point to unmarked objects  */
 375
 376 # define MS_ROOTS_PUSHED 3      /* I holds, mark stack may be nonempty  */
 377
 378 # define MS_PARTIALLY_INVALID 4 /* I may not hold, e.g. because of M.S. */
 379                                 /* overflow.  However marked heap       */
 380                                 /* objects below scan_ptr point to      */
 381                                 /* marked or stacked objects.           */
 382
 383 # define MS_INVALID 5           /* I may not hold.                      */
 384
 385 extern mark_state_t GC_mark_state;
 386
 387 #endif  /* GC_PMARK_H */
 388