1.0.15.35: fix bitrotted GC sanity checks
[sbcl.git] / src / runtime / gencgc.c
index a4f5f7c..79c8d77 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * GENerational Conservative Garbage Collector for SBCL x86
+ * GENerational Conservative Garbage Collector for SBCL
  */
 
 /*
@@ -24,6 +24,7 @@
  *   <ftp://ftp.cs.utexas.edu/pub/garbage/bigsurv.ps>.
  */
 
+#include <stdlib.h>
 #include <stdio.h>
 #include <signal.h>
 #include <errno.h>
 #include "gc.h"
 #include "gc-internal.h"
 #include "thread.h"
+#include "alloc.h"
 #include "genesis/vector.h"
 #include "genesis/weak-pointer.h"
+#include "genesis/fdefn.h"
 #include "genesis/simple-fun.h"
 #include "save.h"
 #include "genesis/hash-table.h"
 #include "genesis/instance.h"
 #include "genesis/layout.h"
+#include "gencgc.h"
+#if defined(LUTEX_WIDETAG)
+#include "pthread-lutex.h"
+#endif
 
 /* forward declarations */
 page_index_t  gc_find_freeish_pages(long *restart_page_ptr, long nbytes,
@@ -73,7 +80,7 @@ enum {
 boolean enable_page_protection = 1;
 
 /* the minimum size (in bytes) for a large object*/
-unsigned long large_object_size = 4 * PAGE_BYTES;
+long large_object_size = 4 * PAGE_BYTES;
 
 \f
 /*
@@ -139,7 +146,6 @@ boolean gencgc_partial_pickup = 0;
 
 /* the total bytes allocated. These are seen by Lisp DYNAMIC-USAGE. */
 unsigned long bytes_allocated = 0;
-extern unsigned long bytes_consed_between_gcs; /* gc-common.c */
 unsigned long auto_gc_trigger = 0;
 
 /* the source and destination generations. These are set before a GC starts
@@ -147,25 +153,23 @@ unsigned long auto_gc_trigger = 0;
 generation_index_t from_space;
 generation_index_t new_space;
 
+/* Set to 1 when in GC */
+boolean gc_active_p = 0;
+
 /* should the GC be conservative on stack. If false (only right before
  * saving a core), don't scan the stack / mark pages dont_move. */
 static boolean conservative_stack = 1;
 
-/* An array of page structures is statically allocated.
+/* An array of page structures is allocated on gc initialization.
  * This helps quickly map between an address its page structure.
- * NUM_PAGES is set from the size of the dynamic space. */
-struct page page_table[NUM_PAGES];
+ * page_table_pages is set from the size of the dynamic space. */
+page_index_t page_table_pages;
+struct page *page_table;
 
 /* To map addresses to page structures the address of the first page
  * is needed. */
 static void *heap_base = NULL;
 
-#if N_WORD_BITS == 32
- #define SIMPLE_ARRAY_WORD_WIDETAG SIMPLE_ARRAY_UNSIGNED_BYTE_32_WIDETAG
-#elif N_WORD_BITS == 64
- #define SIMPLE_ARRAY_WORD_WIDETAG SIMPLE_ARRAY_UNSIGNED_BYTE_64_WIDETAG
-#endif
-
 /* Calculate the start address for the given page number. */
 inline void *
 page_address(page_index_t page_num)
@@ -182,7 +186,7 @@ find_page_index(void *addr)
 
     if (index >= 0) {
         index = ((unsigned long)index)/PAGE_BYTES;
-        if (index < NUM_PAGES)
+        if (index < page_table_pages)
             return (index);
     }
 
@@ -234,6 +238,14 @@ struct generation {
      * prevent a GC when a large number of new live objects have been
      * added, in which case a GC could be a waste of time */
     double min_av_mem_age;
+
+    /* A linked list of lutex structures in this generation, used for
+     * implementing lutex finalization. */
+#ifdef LUTEX_WIDETAG
+    struct lutex *lutexes;
+#else
+    void *lutexes;
+#endif
 };
 
 /* an array of generation structures. There needs to be one more
@@ -301,7 +313,7 @@ count_generation_pages(generation_index_t generation)
     long count = 0;
 
     for (i = 0; i < last_free_page; i++)
-        if ((page_table[i].allocated != 0)
+        if ((page_table[i].allocated != FREE_PAGE_FLAG)
             && (page_table[i].gen == generation))
             count++;
     return count;
@@ -314,7 +326,8 @@ count_dont_move_pages(void)
     page_index_t i;
     long count = 0;
     for (i = 0; i < last_free_page; i++) {
-        if ((page_table[i].allocated != 0) && (page_table[i].dont_move != 0)) {
+        if ((page_table[i].allocated != FREE_PAGE_FLAG)
+            && (page_table[i].dont_move != 0)) {
             ++count;
         }
     }
@@ -330,7 +343,8 @@ count_generation_bytes_allocated (generation_index_t gen)
     page_index_t i;
     long result = 0;
     for (i = 0; i < last_free_page; i++) {
-        if ((page_table[i].allocated != 0) && (page_table[i].gen == gen))
+        if ((page_table[i].allocated != FREE_PAGE_FLAG)
+            && (page_table[i].gen == gen))
             result += page_table[i].bytes_used;
     }
     return result;
@@ -410,17 +424,19 @@ print_generation_stats(int verbose) /* FIXME: should take FILE argument */
         gc_assert(generations[i].bytes_allocated
                   == count_generation_bytes_allocated(i));
         fprintf(stderr,
-                "   %1d: %5ld %5ld %5ld %5ld %5ld %5ld %5ld %5ld %8ld %5ld %8ld %4ld %3d %7.4f\n",
+                "   %1d: %5ld %5ld %5ld %5ld %5ld %5ld %5ld %5ld %5ld %8ld %5ld %8ld %4ld %3d %7.4f\n",
                 i,
                 generations[i].alloc_start_page,
                 generations[i].alloc_unboxed_start_page,
                 generations[i].alloc_large_start_page,
                 generations[i].alloc_large_unboxed_start_page,
-                boxed_cnt, unboxed_cnt, large_boxed_cnt, large_unboxed_cnt,
+                boxed_cnt,
+                unboxed_cnt,
+                large_boxed_cnt,
+                large_unboxed_cnt,
                 pinned_cnt,
                 generations[i].bytes_allocated,
-                (count_generation_pages(i)*PAGE_BYTES
-                 - generations[i].bytes_allocated),
+                (count_generation_pages(i)*PAGE_BYTES - generations[i].bytes_allocated),
                 generations[i].gc_trigger,
                 count_write_protect_generation_pages(i),
                 generations[i].num_gc,
@@ -580,6 +596,7 @@ gc_alloc_new_region(long nbytes, int unboxed, struct alloc_region *alloc_region)
     page_index_t last_page;
     long bytes_found;
     page_index_t i;
+    int ret;
 
     /*
     FSHOW((stderr,
@@ -591,7 +608,8 @@ gc_alloc_new_region(long nbytes, int unboxed, struct alloc_region *alloc_region)
     gc_assert((alloc_region->first_page == 0)
               && (alloc_region->last_page == -1)
               && (alloc_region->free_pointer == alloc_region->end_addr));
-    thread_mutex_lock(&free_pages_lock);
+    ret = thread_mutex_lock(&free_pages_lock);
+    gc_assert(ret == 0);
     if (unboxed) {
         first_page =
             generations[gc_alloc_generation].alloc_unboxed_start_page;
@@ -652,22 +670,8 @@ gc_alloc_new_region(long nbytes, int unboxed, struct alloc_region *alloc_region)
         /* do we only want to call this on special occasions? like for boxed_region? */
         set_alloc_pointer((lispobj)(((char *)heap_base) + last_free_page*PAGE_BYTES));
     }
-    thread_mutex_unlock(&free_pages_lock);
-
-    /* we can do this after releasing free_pages_lock */
-    if (gencgc_zero_check) {
-        long *p;
-        for (p = (long *)alloc_region->start_addr;
-             p < (long *)alloc_region->end_addr; p++) {
-            if (*p != 0) {
-                /* KLUDGE: It would be nice to use %lx and explicit casts
-                 * (long) in code like this, so that it is less likely to
-                 * break randomly when running on a machine with different
-                 * word sizes. -- WHN 19991129 */
-                lose("The new region at %x is not zero.\n", p);
-            }
-        }
-    }
+    ret = thread_mutex_unlock(&free_pages_lock);
+    gc_assert(ret == 0);
 
 #ifdef READ_PROTECT_FREE_PAGES
     os_protect(page_address(first_page),
@@ -684,6 +688,22 @@ gc_alloc_new_region(long nbytes, int unboxed, struct alloc_region *alloc_region)
     }
 
     zero_dirty_pages(first_page, last_page);
+
+    /* we can do this after releasing free_pages_lock */
+    if (gencgc_zero_check) {
+        long *p;
+        for (p = (long *)alloc_region->start_addr;
+             p < (long *)alloc_region->end_addr; p++) {
+            if (*p != 0) {
+                /* KLUDGE: It would be nice to use %lx and explicit casts
+                 * (long) in code like this, so that it is less likely to
+                 * break randomly when running on a machine with different
+                 * word sizes. -- WHN 19991129 */
+                lose("The new region at %x is not zero (start=%p, end=%p).\n",
+                     p, alloc_region->start_addr, alloc_region->end_addr);
+            }
+        }
+    }
 }
 
 /* If the record_new_objects flag is 2 then all new regions created
@@ -794,6 +814,7 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
     long orig_first_page_bytes_used;
     long region_size;
     long byte_cnt;
+    int ret;
 
 
     first_page = alloc_region->first_page;
@@ -804,7 +825,8 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
 
     next_page = first_page+1;
 
-    thread_mutex_lock(&free_pages_lock);
+    ret = thread_mutex_lock(&free_pages_lock);
+    gc_assert(ret == 0);
     if (alloc_region->free_pointer != alloc_region->start_addr) {
         /* some bytes were allocated in the region */
         orig_first_page_bytes_used = page_table[first_page].bytes_used;
@@ -908,7 +930,9 @@ gc_alloc_update_page_tables(int unboxed, struct alloc_region *alloc_region)
         page_table[next_page].allocated = FREE_PAGE_FLAG;
         next_page++;
     }
-    thread_mutex_unlock(&free_pages_lock);
+    ret = thread_mutex_unlock(&free_pages_lock);
+    gc_assert(ret == 0);
+
     /* alloc_region is per-thread, we're ok to do this unlocked */
     gc_set_region_empty(alloc_region);
 }
@@ -926,8 +950,10 @@ gc_alloc_large(long nbytes, int unboxed, struct alloc_region *alloc_region)
     int more;
     long bytes_used;
     page_index_t next_page;
+    int ret;
 
-    thread_mutex_lock(&free_pages_lock);
+    ret = thread_mutex_lock(&free_pages_lock);
+    gc_assert(ret == 0);
 
     if (unboxed) {
         first_page =
@@ -1027,7 +1053,8 @@ gc_alloc_large(long nbytes, int unboxed, struct alloc_region *alloc_region)
         last_free_page = last_page+1;
         set_alloc_pointer((lispobj)(((char *)heap_base) + last_free_page*PAGE_BYTES));
     }
-    thread_mutex_unlock(&free_pages_lock);
+    ret = thread_mutex_unlock(&free_pages_lock);
+    gc_assert(ret == 0);
 
 #ifdef READ_PROTECT_FREE_PAGES
     os_protect(page_address(first_page),
@@ -1042,6 +1069,41 @@ gc_alloc_large(long nbytes, int unboxed, struct alloc_region *alloc_region)
 
 static page_index_t gencgc_alloc_start_page = -1;
 
+void
+gc_heap_exhausted_error_or_lose (long available, long requested)
+{
+    /* Write basic information before doing anything else: if we don't
+     * call to lisp this is a must, and even if we do there is always
+     * the danger that we bounce back here before the error has been
+     * handled, or indeed even printed.
+     */
+    fprintf(stderr, "Heap exhausted during %s: %ld bytes available, %ld requested.\n",
+            gc_active_p ? "garbage collection" : "allocation", available, requested);
+    if (gc_active_p || (available == 0)) {
+        /* If we are in GC, or totally out of memory there is no way
+         * to sanely transfer control to the lisp-side of things.
+         */
+        struct thread *thread = arch_os_get_current_thread();
+        print_generation_stats(1);
+        fprintf(stderr, "GC control variables:\n");
+        fprintf(stderr, "          *GC-INHIBIT* = %s\n          *GC-PENDING* = %s\n",
+                SymbolValue(GC_INHIBIT,thread)==NIL ? "false" : "true",
+                SymbolValue(GC_PENDING,thread)==NIL ? "false" : "true");
+#ifdef LISP_FEATURE_SB_THREAD
+        fprintf(stderr, " *STOP-FOR-GC-PENDING* = %s\n",
+                SymbolValue(STOP_FOR_GC_PENDING,thread)==NIL ? "false" : "true");
+#endif
+        lose("Heap exhausted, game over.");
+    }
+    else {
+        /* FIXME: assert free_pages_lock held */
+        (void)thread_mutex_unlock(&free_pages_lock);
+        funcall2(StaticSymbolFunction(HEAP_EXHAUSTED_ERROR),
+                 alloc_number(available), alloc_number(requested));
+        lose("HEAP-EXHAUSTED-ERROR fell through");
+    }
+}
+
 page_index_t
 gc_find_freeish_pages(page_index_t *restart_page_ptr, long nbytes, int unboxed)
 {
@@ -1065,11 +1127,11 @@ gc_find_freeish_pages(page_index_t *restart_page_ptr, long nbytes, int unboxed)
     do {
         first_page = restart_page;
         if (large_p)
-            while ((first_page < NUM_PAGES)
+            while ((first_page < page_table_pages)
                    && (page_table[first_page].allocated != FREE_PAGE_FLAG))
                 first_page++;
         else
-            while (first_page < NUM_PAGES) {
+            while (first_page < page_table_pages) {
                 if(page_table[first_page].allocated == FREE_PAGE_FLAG)
                     break;
                 if((page_table[first_page].allocated ==
@@ -1084,13 +1146,8 @@ gc_find_freeish_pages(page_index_t *restart_page_ptr, long nbytes, int unboxed)
                 first_page++;
             }
 
-        if (first_page >= NUM_PAGES) {
-            fprintf(stderr,
-                    "Argh! gc_find_free_space failed (first_page), nbytes=%ld.\n",
-                    nbytes);
-            print_generation_stats(1);
-            lose("\n");
-        }
+        if (first_page >= page_table_pages)
+            gc_heap_exhausted_error_or_lose(0, nbytes);
 
         gc_assert(page_table[first_page].write_protected == 0);
 
@@ -1099,7 +1156,7 @@ gc_find_freeish_pages(page_index_t *restart_page_ptr, long nbytes, int unboxed)
         num_pages = 1;
         while (((bytes_found < nbytes)
                 || (!large_p && (num_pages < 2)))
-               && (last_page < (NUM_PAGES-1))
+               && (last_page < (page_table_pages-1))
                && (page_table[last_page+1].allocated == FREE_PAGE_FLAG)) {
             last_page++;
             num_pages++;
@@ -1112,16 +1169,12 @@ gc_find_freeish_pages(page_index_t *restart_page_ptr, long nbytes, int unboxed)
 
         gc_assert(bytes_found == region_size);
         restart_page = last_page + 1;
-    } while ((restart_page < NUM_PAGES) && (bytes_found < nbytes));
+    } while ((restart_page < page_table_pages) && (bytes_found < nbytes));
 
     /* Check for a failure */
-    if ((restart_page >= NUM_PAGES) && (bytes_found < nbytes)) {
-        fprintf(stderr,
-                "Argh! gc_find_freeish_pages failed (restart_page), nbytes=%ld.\n",
-                nbytes);
-        print_generation_stats(1);
-        lose("\n");
-    }
+    if ((restart_page >= page_table_pages) && (bytes_found < nbytes))
+        gc_heap_exhausted_error_or_lose(bytes_found, nbytes);
+
     *restart_page_ptr=first_page;
 
     return last_page;
@@ -1136,7 +1189,7 @@ gc_alloc_with_region(long nbytes,int unboxed_p, struct alloc_region *my_region,
 {
     void *new_free_pointer;
 
-    if(nbytes>=large_object_size)
+    if (nbytes>=large_object_size)
         return gc_alloc_large(nbytes,unboxed_p,my_region);
 
     /* Check whether there is room in the current alloc region. */
@@ -1518,6 +1571,8 @@ sniff_code_object(struct code *code, unsigned long displacement)
     if (!check_code_fixups)
         return;
 
+    FSHOW((stderr, "/sniffing code: %p, %lu\n", code, displacement));
+
     ncode_words = fixnum_value(code->code_size);
     nheader_words = HeaderValue(*(lispobj *)code);
     nwords = ncode_words + nheader_words;
@@ -1765,7 +1820,9 @@ gencgc_apply_code_fixups(struct code *old_code, struct code *new_code)
                     old_value - displacement;
         }
     } else {
-        fprintf(stderr, "widetag of fixup vector is %d\n", widetag_of(fixups_vector->header));
+        /* This used to just print a note to stderr, but a bogus fixup seems to
+         * indicate real heap corruption, so a hard hailure is in order. */
+        lose("fixup vector %p has a bad widetag: %d\n", fixups_vector, widetag_of(fixups_vector->header));
     }
 
     /* Check for possible errors. */
@@ -1811,234 +1868,177 @@ trans_unboxed_large(lispobj object)
 
 \f
 /*
- * vector-like objects
+ * Lutexes. Using the normal finalization machinery for finalizing
+ * lutexes is tricky, since the finalization depends on working lutexes.
+ * So we track the lutexes in the GC and finalize them manually.
  */
 
+#if defined(LUTEX_WIDETAG)
 
-/* FIXME: What does this mean? */
-int gencgc_hash = 1;
+/*
+ * Start tracking LUTEX in the GC, by adding it to the linked list of
+ * lutexes in the nursery generation. The caller is responsible for
+ * locking, and GCs must be inhibited until the registration is
+ * complete.
+ */
+void
+gencgc_register_lutex (struct lutex *lutex) {
+    int index = find_page_index(lutex);
+    generation_index_t gen;
+    struct lutex *head;
 
-#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
+    /* This lutex is in static space, so we don't need to worry about
+     * finalizing it.
+     */
+    if (index == -1)
+        return;
 
-static long
-scav_vector(lispobj *where, lispobj object)
-{
-    unsigned long kv_length;
-    lispobj *kv_vector;
-    unsigned long length = 0; /* (0 = dummy to stop GCC warning) */
-    struct hash_table *hash_table;
-    lispobj empty_symbol;
-    unsigned long *index_vector = NULL; /* (NULL = dummy to stop GCC warning) */
-    unsigned long *next_vector = NULL; /* (NULL = dummy to stop GCC warning) */
-    unsigned long *hash_vector = NULL; /* (NULL = dummy to stop GCC warning) */
-    lispobj weak_p_obj;
-    unsigned long next_vector_length = 0;
-
-    /* FIXME: A comment explaining this would be nice. It looks as
-     * though SB-VM:VECTOR-VALID-HASHING-SUBTYPE is set for EQ-based
-     * hash tables in the Lisp HASH-TABLE code, and nowhere else. */
-    if (HeaderValue(object) != subtype_VectorValidHashing)
-        return 1;
+    gen = page_table[index].gen;
 
-    if (!gencgc_hash) {
-        /* This is set for backward compatibility. FIXME: Do we need
-         * this any more? */
-        *where =
-            (subtype_VectorMustRehash<<N_WIDETAG_BITS) | SIMPLE_VECTOR_WIDETAG;
-        return 1;
-    }
+    gc_assert(gen >= 0);
+    gc_assert(gen < NUM_GENERATIONS);
 
-    kv_length = fixnum_value(where[1]);
-    kv_vector = where + 2;  /* Skip the header and length. */
-    /*FSHOW((stderr,"/kv_length = %d\n", kv_length));*/
+    head = generations[gen].lutexes;
 
-    /* Scavenge element 0, which may be a hash-table structure. */
-    scavenge(where+2, 1);
-    if (!is_lisp_pointer(where[2])) {
-        lose("no pointer at %x in hash table\n", where[2]);
-    }
-    hash_table = (struct hash_table *)native_pointer(where[2]);
-    /*FSHOW((stderr,"/hash_table = %x\n", hash_table));*/
-    if (widetag_of(hash_table->header) != INSTANCE_HEADER_WIDETAG) {
-        lose("hash table not instance (%x at %x)\n",
-             hash_table->header,
-             hash_table);
-    }
+    lutex->gen = gen;
+    lutex->next = head;
+    lutex->prev = NULL;
+    if (head)
+        head->prev = lutex;
+    generations[gen].lutexes = lutex;
+}
 
-    /* Scavenge element 1, which should be some internal symbol that
-     * the hash table code reserves for marking empty slots. */
-    scavenge(where+3, 1);
-    if (!is_lisp_pointer(where[3])) {
-        lose("not empty-hash-table-slot symbol pointer: %x\n", where[3]);
-    }
-    empty_symbol = where[3];
-    /* fprintf(stderr,"* empty_symbol = %x\n", empty_symbol);*/
-    if (widetag_of(*(lispobj *)native_pointer(empty_symbol)) !=
-        SYMBOL_HEADER_WIDETAG) {
-        lose("not a symbol where empty-hash-table-slot symbol expected: %x\n",
-             *(lispobj *)native_pointer(empty_symbol));
+/*
+ * Stop tracking LUTEX in the GC by removing it from the appropriate
+ * linked lists. This will only be called during GC, so no locking is
+ * needed.
+ */
+void
+gencgc_unregister_lutex (struct lutex *lutex) {
+    if (lutex->prev) {
+        lutex->prev->next = lutex->next;
+    } else {
+        generations[lutex->gen].lutexes = lutex->next;
     }
 
-    /* Scavenge hash table, which will fix the positions of the other
-     * needed objects. */
-    scavenge((lispobj *)hash_table,
-             sizeof(struct hash_table) / sizeof(lispobj));
-
-    /* Cross-check the kv_vector. */
-    if (where != (lispobj *)native_pointer(hash_table->table)) {
-        lose("hash_table table!=this table %x\n", hash_table->table);
+    if (lutex->next) {
+        lutex->next->prev = lutex->prev;
     }
 
-    /* WEAK-P */
-    weak_p_obj = hash_table->weak_p;
+    lutex->next = NULL;
+    lutex->prev = NULL;
+    lutex->gen = -1;
+}
 
-    /* index vector */
-    {
-        lispobj index_vector_obj = hash_table->index_vector;
-
-        if (is_lisp_pointer(index_vector_obj) &&
-            (widetag_of(*(lispobj *)native_pointer(index_vector_obj)) ==
-                 SIMPLE_ARRAY_WORD_WIDETAG)) {
-            index_vector =
-                ((unsigned long *)native_pointer(index_vector_obj)) + 2;
-            /*FSHOW((stderr, "/index_vector = %x\n",index_vector));*/
-            length = fixnum_value(((lispobj *)native_pointer(index_vector_obj))[1]);
-            /*FSHOW((stderr, "/length = %d\n", length));*/
-        } else {
-            lose("invalid index_vector %x\n", index_vector_obj);
-        }
-    }
+/*
+ * Mark all lutexes in generation GEN as not live.
+ */
+static void
+unmark_lutexes (generation_index_t gen) {
+    struct lutex *lutex = generations[gen].lutexes;
 
-    /* next vector */
-    {
-        lispobj next_vector_obj = hash_table->next_vector;
-
-        if (is_lisp_pointer(next_vector_obj) &&
-            (widetag_of(*(lispobj *)native_pointer(next_vector_obj)) ==
-             SIMPLE_ARRAY_WORD_WIDETAG)) {
-            next_vector = ((unsigned long *)native_pointer(next_vector_obj)) + 2;
-            /*FSHOW((stderr, "/next_vector = %x\n", next_vector));*/
-            next_vector_length = fixnum_value(((lispobj *)native_pointer(next_vector_obj))[1]);
-            /*FSHOW((stderr, "/next_vector_length = %d\n", next_vector_length));*/
-        } else {
-            lose("invalid next_vector %x\n", next_vector_obj);
-        }
+    while (lutex) {
+        lutex->live = 0;
+        lutex = lutex->next;
     }
+}
 
-    /* maybe hash vector */
-    {
-        lispobj hash_vector_obj = hash_table->hash_vector;
-
-        if (is_lisp_pointer(hash_vector_obj) &&
-            (widetag_of(*(lispobj *)native_pointer(hash_vector_obj)) ==
-             SIMPLE_ARRAY_WORD_WIDETAG)){
-            hash_vector =
-                ((unsigned long *)native_pointer(hash_vector_obj)) + 2;
-            /*FSHOW((stderr, "/hash_vector = %x\n", hash_vector));*/
-            gc_assert(fixnum_value(((lispobj *)native_pointer(hash_vector_obj))[1])
-                      == next_vector_length);
-        } else {
-            hash_vector = NULL;
-            /*FSHOW((stderr, "/no hash_vector: %x\n", hash_vector_obj));*/
+/*
+ * Finalize all lutexes in generation GEN that have not been marked live.
+ */
+static void
+reap_lutexes (generation_index_t gen) {
+    struct lutex *lutex = generations[gen].lutexes;
+
+    while (lutex) {
+        struct lutex *next = lutex->next;
+        if (!lutex->live) {
+            lutex_destroy((tagged_lutex_t) lutex);
+            gencgc_unregister_lutex(lutex);
         }
+        lutex = next;
     }
+}
 
-    /* These lengths could be different as the index_vector can be a
-     * different length from the others, a larger index_vector could help
-     * reduce collisions. */
-    gc_assert(next_vector_length*2 == kv_length);
+/*
+ * Mark LUTEX as live.
+ */
+static void
+mark_lutex (lispobj tagged_lutex) {
+    struct lutex *lutex = (struct lutex*) native_pointer(tagged_lutex);
 
-    /* now all set up.. */
+    lutex->live = 1;
+}
 
-    /* Work through the KV vector. */
-    {
-        long i;
-        for (i = 1; i < next_vector_length; i++) {
-            lispobj old_key = kv_vector[2*i];
+/*
+ * Move all lutexes in generation FROM to generation TO.
+ */
+static void
+move_lutexes (generation_index_t from, generation_index_t to) {
+    struct lutex *tail = generations[from].lutexes;
 
-#if N_WORD_BITS == 32
-            unsigned long old_index = (old_key & 0x1fffffff)%length;
-#elif N_WORD_BITS == 64
-            unsigned long old_index = (old_key & 0x1fffffffffffffff)%length;
-#endif
+    /* Nothing to move */
+    if (!tail)
+        return;
 
-            /* Scavenge the key and value. */
-            scavenge(&kv_vector[2*i],2);
+    /* Change the generation of the lutexes in FROM. */
+    while (tail->next) {
+        tail->gen = to;
+        tail = tail->next;
+    }
+    tail->gen = to;
 
-            /* Check whether the key has moved and is EQ based. */
-            {
-                lispobj new_key = kv_vector[2*i];
-#if N_WORD_BITS == 32
-                unsigned long new_index = (new_key & 0x1fffffff)%length;
-#elif N_WORD_BITS == 64
-                unsigned long new_index = (new_key & 0x1fffffffffffffff)%length;
-#endif
+    /* Link the last lutex in the FROM list to the start of the TO list */
+    tail->next = generations[to].lutexes;
 
-                if ((old_index != new_index) &&
-                    ((!hash_vector) ||
-                     (hash_vector[i] == MAGIC_HASH_VECTOR_VALUE)) &&
-                    ((new_key != empty_symbol) ||
-                     (kv_vector[2*i] != empty_symbol))) {
-
-                     /*FSHOW((stderr,
-                            "* EQ key %d moved from %x to %x; index %d to %d\n",
-                            i, old_key, new_key, old_index, new_index));*/
-
-                    if (index_vector[old_index] != 0) {
-                         /*FSHOW((stderr, "/P1 %d\n", index_vector[old_index]));*/
-
-                        /* Unlink the key from the old_index chain. */
-                        if (index_vector[old_index] == i) {
-                            /*FSHOW((stderr, "/P2a %d\n", next_vector[i]));*/
-                            index_vector[old_index] = next_vector[i];
-                            /* Link it into the needing rehash chain. */
-                            next_vector[i] = fixnum_value(hash_table->needing_rehash);
-                            hash_table->needing_rehash = make_fixnum(i);
-                            /*SHOW("P2");*/
-                        } else {
-                            unsigned long prior = index_vector[old_index];
-                            unsigned long next = next_vector[prior];
-
-                            /*FSHOW((stderr, "/P3a %d %d\n", prior, next));*/
-
-                            while (next != 0) {
-                                 /*FSHOW((stderr, "/P3b %d %d\n", prior, next));*/
-                                if (next == i) {
-                                    /* Unlink it. */
-                                    next_vector[prior] = next_vector[next];
-                                    /* Link it into the needing rehash
-                                     * chain. */
-                                    next_vector[next] =
-                                        fixnum_value(hash_table->needing_rehash);
-                                    hash_table->needing_rehash = make_fixnum(next);
-                                    /*SHOW("/P3");*/
-                                    break;
-                                }
-                                prior = next;
-                                next = next_vector[next];
-                            }
-                        }
-                    }
-                }
-            }
-        }
+    /* And vice versa */
+    if (generations[to].lutexes) {
+        generations[to].lutexes->prev = tail;
     }
-    return (CEILING(kv_length + 2, 2));
-}
 
-#else
+    /* And update the generations structures to match this */
+    generations[to].lutexes = generations[from].lutexes;
+    generations[from].lutexes = NULL;
+}
 
 static long
-scav_vector(lispobj *where, lispobj object)
+scav_lutex(lispobj *where, lispobj object)
+{
+    mark_lutex((lispobj) where);
+
+    return CEILING(sizeof(struct lutex)/sizeof(lispobj), 2);
+}
+
+static lispobj
+trans_lutex(lispobj object)
 {
-    if (HeaderValue(object) == subtype_VectorValidHashing) {
-        *where =
-            (subtype_VectorMustRehash<<N_WIDETAG_BITS) | SIMPLE_VECTOR_WIDETAG;
+    struct lutex *lutex = (struct lutex *) native_pointer(object);
+    lispobj copied;
+    size_t words = CEILING(sizeof(struct lutex)/sizeof(lispobj), 2);
+    gc_assert(is_lisp_pointer(object));
+    copied = copy_object(object, words);
+
+    /* Update the links, since the lutex moved in memory. */
+    if (lutex->next) {
+        lutex->next->prev = (struct lutex *) native_pointer(copied);
     }
-    return 1;
+
+    if (lutex->prev) {
+        lutex->prev->next = (struct lutex *) native_pointer(copied);
+    } else {
+        generations[lutex->gen].lutexes =
+          (struct lutex *) native_pointer(copied);
+    }
+
+    return copied;
 }
 
-#endif
+static long
+size_lutex(lispobj *where)
+{
+    return CEILING(sizeof(struct lutex)/sizeof(lispobj), 2);
+}
+#endif /* LUTEX_WIDETAG */
 
 \f
 /*
@@ -2056,29 +2056,21 @@ scav_vector(lispobj *where, lispobj object)
 static long
 scav_weak_pointer(lispobj *where, lispobj object)
 {
-    struct weak_pointer *wp = weak_pointers;
-    /* Push the weak pointer onto the list of weak pointers.
-     * Do I have to watch for duplicates? Originally this was
-     * part of trans_weak_pointer but that didn't work in the
-     * case where the WP was in a promoted region.
+    /* Since we overwrite the 'next' field, we have to make
+     * sure not to do so for pointers already in the list.
+     * Instead of searching the list of weak_pointers each
+     * time, we ensure that next is always NULL when the weak
+     * pointer isn't in the list, and not NULL otherwise.
+     * Since we can't use NULL to denote end of list, we
+     * use a pointer back to the same weak_pointer.
      */
+    struct weak_pointer * wp = (struct weak_pointer*)where;
 
-    /* Check whether it's already in the list. */
-    while (wp != NULL) {
-        if (wp == (struct weak_pointer*)where) {
-            break;
-        }
-        wp = wp->next;
-    }
-    if (wp == NULL) {
-        /* Add it to the start of the list. */
-        wp = (struct weak_pointer*)where;
-        if (wp->next != weak_pointers) {
-            wp->next = weak_pointers;
-        } else {
-            /*SHOW("avoided write to weak pointer");*/
-        }
+    if (NULL == wp->next) {
+        wp->next = weak_pointers;
         weak_pointers = wp;
+        if (NULL == wp->next)
+            wp->next = wp;
     }
 
     /* Do not let GC scavenge the value slot of the weak pointer.
@@ -2131,37 +2123,30 @@ search_dynamic_space(void *pointer)
                             (lispobj *)pointer));
 }
 
-/* Is there any possibility that pointer is a valid Lisp object
- * reference, and/or something else (e.g. subroutine call return
- * address) which should prevent us from moving the referred-to thing?
- * This is called from preserve_pointers() */
+#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
+
+/* Helper for valid_lisp_pointer_p and
+ * possibly_valid_dynamic_space_pointer.
+ *
+ * pointer is the pointer to validate, and start_addr is the address
+ * of the enclosing object.
+ */
 static int
-possibly_valid_dynamic_space_pointer(lispobj *pointer)
+looks_like_valid_lisp_pointer_p(lispobj *pointer, lispobj *start_addr)
 {
-    lispobj *start_addr;
-
-    /* Find the object start address. */
-    if ((start_addr = search_dynamic_space(pointer)) == NULL) {
-        return 0;
-    }
-
     /* We need to allow raw pointers into Code objects for return
      * addresses. This will also pick up pointers to functions in code
      * objects. */
-    if (widetag_of(*start_addr) == CODE_HEADER_WIDETAG) {
+    if (widetag_of(*start_addr) == CODE_HEADER_WIDETAG)
         /* XXX could do some further checks here */
         return 1;
-    }
 
-    /* If it's not a return address then it needs to be a valid Lisp
-     * pointer. */
     if (!is_lisp_pointer((lispobj)pointer)) {
         return 0;
     }
 
     /* Check that the object pointed to is consistent with the pointer
-     * low tag.
-     */
+     * low tag. */
     switch (lowtag_of((lispobj)pointer)) {
     case FUN_POINTER_LOWTAG:
         /* Start_addr should be the enclosing code object, or a closure
@@ -2378,6 +2363,9 @@ possibly_valid_dynamic_space_pointer(lispobj *pointer)
 #endif
         case SAP_WIDETAG:
         case WEAK_POINTER_WIDETAG:
+#ifdef LUTEX_WIDETAG
+        case LUTEX_WIDETAG:
+#endif
             break;
 
         default:
@@ -2400,7 +2388,46 @@ possibly_valid_dynamic_space_pointer(lispobj *pointer)
     return 1;
 }
 
-#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
+/* Used by the debugger to validate possibly bogus pointers before
+ * calling MAKE-LISP-OBJ on them.
+ *
+ * FIXME: We would like to make this perfect, because if the debugger
+ * constructs a reference to a bugs lisp object, and it ends up in a
+ * location scavenged by the GC all hell breaks loose.
+ *
+ * Whereas possibly_valid_dynamic_space_pointer has to be conservative
+ * and return true for all valid pointers, this could actually be eager
+ * and lie about a few pointers without bad results... but that should
+ * be reflected in the name.
+ */
+int
+valid_lisp_pointer_p(lispobj *pointer)
+{
+    lispobj *start;
+    if (((start=search_dynamic_space(pointer))!=NULL) ||
+        ((start=search_static_space(pointer))!=NULL) ||
+        ((start=search_read_only_space(pointer))!=NULL))
+        return looks_like_valid_lisp_pointer_p(pointer, start);
+    else
+        return 0;
+}
+
+/* Is there any possibility that pointer is a valid Lisp object
+ * reference, and/or something else (e.g. subroutine call return
+ * address) which should prevent us from moving the referred-to thing?
+ * This is called from preserve_pointers() */
+static int
+possibly_valid_dynamic_space_pointer(lispobj *pointer)
+{
+    lispobj *start_addr;
+
+    /* Find the object start address. */
+    if ((start_addr = search_dynamic_space(pointer)) == NULL) {
+        return 0;
+    }
+
+    return looks_like_valid_lisp_pointer_p(pointer, start_addr);
+}
 
 /* Adjust large bignum and vector objects. This will adjust the
  * allocated region if the size has shrunk, and move unboxed objects
@@ -2576,8 +2603,6 @@ maybe_adjust_large_object(lispobj *where)
     return;
 }
 
-#endif
-
 /* Take a possible pointer to a Lisp object and mark its page in the
  * page_table so that it will not be relocated during a GC.
  *
@@ -2591,8 +2616,6 @@ maybe_adjust_large_object(lispobj *where)
  * It is also assumed that the current gc_alloc() region has been
  * flushed and the tables updated. */
 
-#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
-
 static void
 preserve_pointer(void *addr)
 {
@@ -2709,7 +2732,7 @@ preserve_pointer(void *addr)
     gc_assert(page_table[addr_page_index].dont_move != 0);
 }
 
-#endif
+#endif  // defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
 
 \f
 /* If the given page is not write-protected, then scan it for pointers
@@ -2823,7 +2846,7 @@ scavenge_generations(generation_index_t from, generation_index_t to)
 #define SC_GEN_CK 0
 #if SC_GEN_CK
     /* Clear the write_protected_cleared flags on all pages. */
-    for (i = 0; i < NUM_PAGES; i++)
+    for (i = 0; i < page_table_pages; i++)
         page_table[i].write_protected_cleared = 0;
 #endif
 
@@ -2877,7 +2900,7 @@ scavenge_generations(generation_index_t from, generation_index_t to)
 #if SC_GEN_CK
     /* Check that none of the write_protected pages in this generation
      * have been written to. */
-    for (i = 0; i < NUM_PAGES; i++) {
+    for (i = 0; i < page_table_pages; i++) {
         if ((page_table[i].allocation != FREE_PAGE_FLAG)
             && (page_table[i].bytes_used != 0)
             && (page_table[i].gen == generation)
@@ -3020,6 +3043,13 @@ scavenge_newspace_generation(generation_index_t generation)
     /* Record all new areas now. */
     record_new_objects = 2;
 
+    /* Give a chance to weak hash tables to make other objects live.
+     * FIXME: The algorithm implemented here for weak hash table gcing
+     * is O(W^2+N) as Bruno Haible warns in
+     * http://www.haible.de/bruno/papers/cs/weak/WeakDatastructures-writeup.html
+     * see "Implementation 2". */
+    scav_weak_hash_tables();
+
     /* Flush the current regions updating the tables. */
     gc_alloc_update_all_page_tables();
 
@@ -3058,8 +3088,8 @@ scavenge_newspace_generation(generation_index_t generation)
             if (gencgc_verbose)
                 SHOW("new_areas overflow, doing full scavenge");
 
-            /* Don't need to record new areas that get scavenge anyway
-             * during scavenge_newspace_generation_one_scan. */
+            /* Don't need to record new areas that get scavenged
+             * anyway during scavenge_newspace_generation_one_scan. */
             record_new_objects = 1;
 
             scavenge_newspace_generation_one_scan(generation);
@@ -3067,6 +3097,8 @@ scavenge_newspace_generation(generation_index_t generation)
             /* Record all new areas now. */
             record_new_objects = 2;
 
+            scav_weak_hash_tables();
+
             /* Flush the current regions updating the tables. */
             gc_alloc_update_all_page_tables();
 
@@ -3081,6 +3113,8 @@ scavenge_newspace_generation(generation_index_t generation)
                 scavenge(page_address(page)+offset, size);
             }
 
+            scav_weak_hash_tables();
+
             /* Flush the current regions updating the tables. */
             gc_alloc_update_all_page_tables();
         }
@@ -3098,7 +3132,7 @@ scavenge_newspace_generation(generation_index_t generation)
 #if SC_NS_GEN_CK
     /* Check that none of the write_protected pages in this generation
      * have been written to. */
-    for (i = 0; i < NUM_PAGES; i++) {
+    for (i = 0; i < page_table_pages; i++) {
         if ((page_table[i].allocation != FREE_PAGE_FLAG)
             && (page_table[i].bytes_used != 0)
             && (page_table[i].gen == generation)
@@ -3232,13 +3266,6 @@ print_ptr(lispobj *addr)
 }
 #endif
 
-#if defined(LISP_FEATURE_PPC)
-extern int closure_tramp;
-extern int undefined_tramp;
-#else
-extern int undefined_tramp;
-#endif
-
 static void
 verify_space(lispobj *start, size_t words)
 {
@@ -3293,14 +3320,7 @@ verify_space(lispobj *start, size_t words)
                 */
             } else {
                 /* Verify that it points to another valid space. */
-                if (!to_readonly_space && !to_static_space &&
-#if defined(LISP_FEATURE_PPC)
-                    !((thing == &closure_tramp) ||
-                      (thing == &undefined_tramp))
-#else
-                    thing != (unsigned long)&undefined_tramp
-#endif
-                    ) {
+                if (!to_readonly_space && !to_static_space) {
                     lose("Ptr %x @ %x sees junk.\n", thing, start);
                 }
             }
@@ -3481,15 +3501,17 @@ verify_space(lispobj *start, size_t words)
 #endif
                 case SAP_WIDETAG:
                 case WEAK_POINTER_WIDETAG:
+#ifdef LUTEX_WIDETAG
+                case LUTEX_WIDETAG:
+#endif
+#ifdef NO_TLS_VALUE_MARKER_WIDETAG
+                case NO_TLS_VALUE_MARKER_WIDETAG:
+#endif
                     count = (sizetab[widetag_of(*start)])(start);
                     break;
 
                 default:
-                    FSHOW((stderr,
-                           "/Unhandled widetag 0x%x at 0x%x\n",
-                           widetag_of(*start), start));
-                    fflush(stderr);
-                    gc_abort();
+                    lose("Unhandled widetag 0x%x at 0x%x\n", widetag_of(*start), start);
                 }
             }
         }
@@ -3665,6 +3687,8 @@ write_protect_generation_pages(generation_index_t generation)
     }
 }
 
+#if !defined(LISP_FEATURE_X86) && !defined(LISP_FEATURE_X86_64)
+
 static void
 scavenge_control_stack()
 {
@@ -3680,7 +3704,6 @@ scavenge_control_stack()
     scavenge(control_stack, control_stack_size);
 }
 
-#if !defined(LISP_FEATURE_X86) && !defined(LISP_FEATURE_X86_64)
 /* Scavenging Interrupt Contexts */
 
 static int boxed_registers[] = BOXED_REGISTERS;
@@ -3817,6 +3840,49 @@ scavenge_interrupt_contexts(void)
 
 #endif
 
+#if defined(LISP_FEATURE_SB_THREAD)
+static void
+preserve_context_registers (os_context_t *c)
+{
+    void **ptr;
+    /* On Darwin the signal context isn't a contiguous block of memory,
+     * so just preserve_pointering its contents won't be sufficient.
+     */
+#if defined(LISP_FEATURE_DARWIN)
+#if defined LISP_FEATURE_X86
+    preserve_pointer((void*)*os_context_register_addr(c,reg_EAX));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_ECX));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_EDX));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_EBX));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_ESI));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_EDI));
+    preserve_pointer((void*)*os_context_pc_addr(c));
+#elif defined LISP_FEATURE_X86_64
+    preserve_pointer((void*)*os_context_register_addr(c,reg_RAX));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_RCX));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_RDX));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_RBX));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_RSI));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_RDI));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_R8));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_R9));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_R10));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_R11));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_R12));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_R13));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_R14));
+    preserve_pointer((void*)*os_context_register_addr(c,reg_R15));
+    preserve_pointer((void*)*os_context_pc_addr(c));
+#else
+    #error "preserve_context_registers needs to be tweaked for non-x86 Darwin"
+#endif
+#endif
+    for(ptr = ((void **)(c+1))-1; ptr>=(void **)c; ptr--) {
+        preserve_pointer(*ptr);
+    }
+}
+#endif
+
 /* Garbage collect a generation. If raise is 0 then the remains of the
  * generation are not raised to the next generation. */
 static void
@@ -3825,15 +3891,24 @@ garbage_collect_generation(generation_index_t generation, int raise)
     unsigned long bytes_freed;
     page_index_t i;
     unsigned long static_space_size;
+#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
     struct thread *th;
+#endif
     gc_assert(generation <= HIGHEST_NORMAL_GENERATION);
 
     /* The oldest generation can't be raised. */
     gc_assert((generation != HIGHEST_NORMAL_GENERATION) || (raise == 0));
 
+    /* Check if weak hash tables were processed in the previous GC. */
+    gc_assert(weak_hash_tables == NULL);
+
     /* Initialize the weak pointer list. */
     weak_pointers = NULL;
 
+#ifdef LUTEX_WIDETAG
+    unmark_lutexes(generation);
+#endif
+
     /* When a generation is not being raised it is transported to a
      * temporary generation (NUM_GENERATIONS), and lowered when
      * done. Set up this new generation. There should be no pages
@@ -3906,16 +3981,14 @@ garbage_collect_generation(generation_index_t generation, int raise)
                     if (esp1>=(void **)th->control_stack_start &&
                         esp1<(void **)th->control_stack_end) {
                         if(esp1<esp) esp=esp1;
-                        for(ptr = (void **)(c+1); ptr>=(void **)c; ptr--) {
-                            preserve_pointer(*ptr);
-                        }
+                        preserve_context_registers(c);
                     }
                 }
             }
 #else
             esp = (void **)((void *)&raise);
 #endif
-            for (ptr = (void **)th->control_stack_end; ptr > esp;  ptr--) {
+            for (ptr = ((void **)th->control_stack_end)-1; ptr >= esp;  ptr--) {
                 preserve_pointer(*ptr);
             }
         }
@@ -4036,6 +4109,7 @@ garbage_collect_generation(generation_index_t generation, int raise)
     }
 #endif
 
+    scan_weak_hash_tables();
     scan_weak_pointers();
 
     /* Flush the current regions, updating the tables. */
@@ -4079,6 +4153,12 @@ garbage_collect_generation(generation_index_t generation, int raise)
         generations[generation].num_gc = 0;
     else
         ++generations[generation].num_gc;
+
+#ifdef LUTEX_WIDETAG
+    reap_lutexes(generation);
+    if (raise)
+        move_lutexes(generation, generation+1);
+#endif
 }
 
 /* Update last_free_page, then SymbolValue(ALLOCATION_POINTER). */
@@ -4152,6 +4232,8 @@ collect_garbage(generation_index_t last_gen)
 
     FSHOW((stderr, "/entering collect_garbage(%d)\n", last_gen));
 
+    gc_active_p = 1;
+
     if (last_gen > HIGHEST_NORMAL_GENERATION+1) {
         FSHOW((stderr,
                "/collect_garbage: last_gen = %d, doing a level 0 GC\n",
@@ -4271,6 +4353,8 @@ collect_garbage(generation_index_t last_gen)
         high_water_mark = 0;
     }
 
+    gc_active_p = 0;
+
     SHOW("returning from collect_garbage");
 }
 
@@ -4287,7 +4371,7 @@ gc_free_heap(void)
     if (gencgc_verbose > 1)
         SHOW("entering gc_free_heap");
 
-    for (page = 0; page < NUM_PAGES; page++) {
+    for (page = 0; page < page_table_pages; page++) {
         /* Skip free pages which should already be zero filled. */
         if (page_table[page].allocated != FREE_PAGE_FLAG) {
             void *page_start, *addr;
@@ -4345,6 +4429,7 @@ gc_free_heap(void)
         generations[page].gc_trigger = 2000000;
         generations[page].num_gc = 0;
         generations[page].cum_sum_bytes_allocated = 0;
+        generations[page].lutexes = NULL;
     }
 
     if (gencgc_verbose > 1)
@@ -4361,8 +4446,7 @@ gc_free_heap(void)
 
     if (verify_after_free_heap) {
         /* Check whether purify has left any bad pointers. */
-        if (gencgc_verbose)
-            SHOW("checking after free_heap\n");
+        FSHOW((stderr, "checking after free_heap\n"));
         verify_gc();
     }
 }
@@ -4372,15 +4456,28 @@ gc_init(void)
 {
     page_index_t i;
 
+    /* Compute the number of pages needed for the dynamic space.
+     * Dynamic space size should be aligned on page size. */
+    page_table_pages = dynamic_space_size/PAGE_BYTES;
+    gc_assert(dynamic_space_size == (size_t) page_table_pages*PAGE_BYTES);
+
+    page_table = calloc(page_table_pages, sizeof(struct page));
+    gc_assert(page_table);
+
     gc_init_tables();
-    scavtab[SIMPLE_VECTOR_WIDETAG] = scav_vector;
     scavtab[WEAK_POINTER_WIDETAG] = scav_weak_pointer;
     transother[SIMPLE_ARRAY_WIDETAG] = trans_boxed_large;
 
+#ifdef LUTEX_WIDETAG
+    scavtab[LUTEX_WIDETAG] = scav_lutex;
+    transother[LUTEX_WIDETAG] = trans_lutex;
+    sizetab[LUTEX_WIDETAG] = size_lutex;
+#endif
+
     heap_base = (void*)DYNAMIC_SPACE_START;
 
     /* Initialize each page structure. */
-    for (i = 0; i < NUM_PAGES; i++) {
+    for (i = 0; i < page_table_pages; i++) {
         /* Initialize all pages as free. */
         page_table[i].allocated = FREE_PAGE_FLAG;
         page_table[i].bytes_used = 0;
@@ -4407,6 +4504,7 @@ gc_init(void)
         generations[i].bytes_consed_between_gc = 2000000;
         generations[i].trigger_age = 1;
         generations[i].min_av_mem_age = 0.75;
+        generations[i].lutexes = NULL;
     }
 
     /* Initialize gc_alloc. */
@@ -4450,6 +4548,13 @@ gencgc_pickup_dynamic(void)
         page++;
     } while ((long)page_address(page) < alloc_ptr);
 
+#ifdef LUTEX_WIDETAG
+    /* Lutexes have been registered in generation 0 by coreparse, and
+     * need to be moved to the right one manually.
+     */
+    move_lutexes(0, PSEUDO_STATIC_GENERATION);
+#endif
+
     last_free_page = page;
 
     generations[gen].bytes_allocated = PAGE_BYTES*page;
@@ -4480,7 +4585,7 @@ gc_initialize_pointers(void)
  * The check for a GC trigger is only performed when the current
  * region is full, so in most cases it's not needed. */
 
-char *
+lispobj *
 alloc(long nbytes)
 {
     struct thread *thread=arch_os_get_current_thread();
@@ -4490,8 +4595,12 @@ alloc(long nbytes)
 #else
         &boxed_region;
 #endif
+#ifndef LISP_FEATURE_WIN32
+    lispobj alloc_signal;
+#endif
     void *new_obj;
     void *new_free_pointer;
+
     gc_assert(nbytes>0);
 
     /* Check for alignment allocation problems. */
@@ -4543,6 +4652,24 @@ alloc(long nbytes)
         }
     }
     new_obj = gc_alloc_with_region(nbytes,0,region,0);
+
+#ifndef LISP_FEATURE_WIN32
+    alloc_signal = SymbolValue(ALLOC_SIGNAL,thread);
+    if ((alloc_signal & FIXNUM_TAG_MASK) == 0) {
+        if ((signed long) alloc_signal <= 0) {
+#ifdef LISP_FEATURE_SB_THREAD
+            kill_thread_safely(thread->os_thread, SIGPROF);
+#else
+            raise(SIGPROF);
+#endif
+        } else {
+            SetSymbolValue(ALLOC_SIGNAL,
+                           alloc_signal - (1 << N_FIXNUM_TAG_BITS),
+                           thread);
+        }
+    }
+#endif
+
     return (new_obj);
 }
 \f
@@ -4551,7 +4678,7 @@ alloc(long nbytes)
  * catch GENCGC-related write-protect violations
  */
 
-void unhandled_sigmemoryfault(void);
+void unhandled_sigmemoryfault(void* addr);
 
 /* Depending on which OS we're running under, different signals might
  * be raised for a violation of write protection in the heap. This
@@ -4578,7 +4705,7 @@ gencgc_handle_wp_violation(void* fault_addr)
 
         /* It can be helpful to be able to put a breakpoint on this
          * case to help diagnose low-level problems. */
-        unhandled_sigmemoryfault();
+        unhandled_sigmemoryfault(fault_addr);
 
         /* not within the dynamic space -- not our responsibility */
         return 0;
@@ -4609,7 +4736,7 @@ gencgc_handle_wp_violation(void* fault_addr)
  * are about to let Lisp deal with it. It's basically just a
  * convenient place to set a gdb breakpoint. */
 void
-unhandled_sigmemoryfault()
+unhandled_sigmemoryfault(void *addr)
 {}
 
 void gc_alloc_update_all_page_tables(void)
@@ -4684,7 +4811,8 @@ gc_and_save(char *filename, int prepend_runtime)
     void *runtime_bytes = NULL;
     size_t runtime_size;
 
-    file = prepare_to_save(filename, prepend_runtime, &runtime_bytes, &runtime_size);
+    file = prepare_to_save(filename, prepend_runtime, &runtime_bytes,
+                           &runtime_size);
     if (file == NULL)
        return;