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-rw-r--r--libguile/gc.h57
1 files changed, 36 insertions, 21 deletions
diff --git a/libguile/gc.h b/libguile/gc.h
index 4cb78a714..baf77fa66 100644
--- a/libguile/gc.h
+++ b/libguile/gc.h
@@ -29,6 +29,34 @@
+/* Cell allocation and garbage collection work rouhgly in the
+ following manner:
+
+ Each thread has a 'freelist', which is a list of available cells.
+ (It actually has two freelists, one for single cells and one for
+ double cells. Everything works analogous for double cells.)
+
+ When a thread wants to allocate a cell and the freelist is empty,
+ it refers to a global list of unswept 'cards'. A card is a small
+ block of cells that are contigous in memory, together with the
+ corresponding mark bits. A unswept card is one where the mark bits
+ are set for cells that have been in use during the last global mark
+ phase, but the unmarked cells of the card have not been scanned and
+ freed yet.
+
+ The thread takes one of the unswept cards and sweeps it, thereby
+ building a new freelist that it then uses. Sweeping a card will
+ call the smob free functions of unmarked cells, for example, and
+ thus, these free functions can run at any time, in any thread.
+
+ When there are no more unswept cards available, the thread performs
+ a global garbage collection. For this, all other threads are
+ stopped. A global mark is performed and all cards are put into the
+ global list of unswept cards. Whennecessary, new cards are
+ allocated and initialized at this time. The other threads are then
+ started again.
+*/
+
typedef struct scm_t_cell
{
SCM word_0;
@@ -66,7 +94,7 @@ typedef struct scm_t_cell
#define SCM_GC_CARD_N_HEADER_CELLS 1
#define SCM_GC_CARD_N_CELLS 256
-#define SCM_GC_SIZEOF_CARD SCM_GC_CARD_N_CELLS * sizeof (scm_t_cell)
+#define SCM_GC_SIZEOF_CARD SCM_GC_CARD_N_CELLS * sizeof (scm_t_cell)
#define SCM_GC_CARD_BVEC(card) ((scm_t_c_bvec_long *) ((card)->word_0))
#define SCM_GC_SET_CARD_BVEC(card, bvec) \
@@ -187,6 +215,10 @@ typedef unsigned long scm_t_c_bvec_long;
#define SCM_SET_CELL_OBJECT_2(x, v) SCM_SET_CELL_OBJECT ((x), 2, (v))
#define SCM_SET_CELL_OBJECT_3(x, v) SCM_SET_CELL_OBJECT ((x), 3, (v))
+#define SCM_CELL_OBJECT_LOC(x, n) (SCM_VALIDATE_CELL((x), &SCM_GC_CELL_OBJECT ((x), (n))))
+#define SCM_CARLOC(x) (SCM_CELL_OBJECT_LOC ((x), 0))
+#define SCM_CDRLOC(x) (SCM_CELL_OBJECT_LOC ((x), 1))
+
#define SCM_CELL_TYPE(x) SCM_CELL_WORD_0 (x)
#define SCM_SET_CELL_TYPE(x, t) SCM_SET_CELL_WORD_0 ((x), (t))
@@ -195,27 +227,11 @@ typedef unsigned long scm_t_c_bvec_long;
* the freelist. Due to this structure, freelist cells are not cons cells
* and thus may not be accessed using SCM_CAR and SCM_CDR. */
-/*
- SCM_FREECELL_P removed ; the semantics are ambiguous with lazy
- sweeping. Could mean "this cell is no longer in use (will be swept)"
- or "this cell has just been swept, and is not yet in use".
- */
-
-#define SCM_FREECELL_P this_macro_has_been_removed_see_gc_header_file
-
#define SCM_FREE_CELL_CDR(x) \
(SCM_GC_CELL_OBJECT ((x), 1))
#define SCM_SET_FREE_CELL_CDR(x, v) \
(SCM_GC_SET_CELL_OBJECT ((x), 1, (v)))
-
-#define SCM_CELL_OBJECT_LOC(x, n) (SCM_VALIDATE_CELL((x), &SCM_GC_CELL_OBJECT ((x), (n))))
-#define SCM_CARLOC(x) (SCM_CELL_OBJECT_LOC ((x), 0))
-#define SCM_CDRLOC(x) (SCM_CELL_OBJECT_LOC ((x), 1))
-
-
-
-
#if (SCM_DEBUG_CELL_ACCESSES == 1)
/* Set this to != 0 if every cell that is accessed shall be checked:
*/
@@ -227,10 +243,9 @@ void scm_i_expensive_validation_check (SCM cell);
SCM_API scm_i_pthread_mutex_t scm_i_gc_admin_mutex;
-SCM_API int scm_block_gc;
-SCM_API int scm_gc_heap_lock;
-SCM_API unsigned int scm_gc_running_p;
+#define scm_gc_running_p (SCM_I_CURRENT_THREAD->gc_running_p)
SCM_API scm_i_pthread_mutex_t scm_i_sweep_mutex;
+
#if (SCM_ENABLE_DEPRECATED == 1)
@@ -305,7 +320,7 @@ SCM_API SCM scm_gc_live_object_stats (void);
SCM_API SCM scm_gc (void);
SCM_API void scm_gc_for_alloc (struct scm_t_cell_type_statistics *freelist);
SCM_API SCM scm_gc_for_newcell (struct scm_t_cell_type_statistics *master, SCM *freelist);
-SCM_API void scm_igc (const char *what);
+SCM_API void scm_i_gc (const char *what);
SCM_API void scm_gc_mark (SCM p);
SCM_API void scm_gc_mark_dependencies (SCM p);
SCM_API void scm_mark_locations (SCM_STACKITEM x[], unsigned long n);