#include "validate.h"
#include "lispregs.h"
#include "arch.h"
-#include "fixnump.h"
#include "gc.h"
#include "genesis/primitive-objects.h"
#include "genesis/static-symbols.h"
#include "genesis/layout.h"
+#include "genesis/hash-table.h"
#include "gc-internal.h"
#ifdef LISP_FEATURE_SPARC
#endif
#endif
+size_t dynamic_space_size = DEFAULT_DYNAMIC_SPACE_SIZE;
+size_t thread_control_stack_size = DEFAULT_CONTROL_STACK_SIZE;
+
inline static boolean
forwarding_pointer_p(lispobj *pointer) {
lispobj first_word=*pointer;
lispobj *end = start + n_words;
lispobj *object_ptr;
long n_words_scavenged;
- for (object_ptr = start;
+ for (object_ptr = start;
object_ptr < end;
object_ptr += n_words_scavenged) {
lispobj object = *object_ptr;
#ifdef LISP_FEATURE_GENCGC
- gc_assert(!forwarding_pointer_p(object_ptr));
+ if (forwarding_pointer_p(object_ptr))
+ lose("unexpect forwarding pointer in scavenge: %p, start=%p, n=%l\n",
+ object_ptr, start, n_words);
#endif
if (is_lisp_pointer(object)) {
if (from_space_p(object)) {
n_words_scavenged = 1;
}
}
-#ifndef LISP_FEATURE_GENCGC
- /* this workaround is probably not necessary for gencgc; at least, the
- * behaviour it describes has never been reported */
- else if (n_words==1) {
- /* there are some situations where an
- other-immediate may end up in a descriptor
- register. I'm not sure whether this is
- supposed to happen, but if it does then we
+#if !defined(LISP_FEATURE_X86) && !defined(LISP_FEATURE_X86_64)
+ /* This workaround is probably not needed for those ports
+ which don't have a partitioned register set (and therefore
+ scan the stack conservatively for roots). */
+ else if (n_words == 1) {
+ /* there are some situations where an other-immediate may
+ end up in a descriptor register. I'm not sure whether
+ this is supposed to happen, but if it does then we
don't want to (a) barf or (b) scavenge over the
- data-block, because there isn't one. So, if
- we're checking a single word and it's anything
- other than a pointer, just hush it up */
- int type=widetag_of(object);
- n_words_scavenged=1;
-
- if ((scavtab[type]==scav_lose) ||
- (((scavtab[type])(start,object))>1)) {
- fprintf(stderr,"warning: attempted to scavenge non-descriptor value %x at %p. If you can\nreproduce this warning, send a bug report (see manual page for details)\n",
- object,start);
+ data-block, because there isn't one. So, if we're
+ checking a single word and it's anything other than a
+ pointer, just hush it up */
+ int widetag = widetag_of(object);
+ n_words_scavenged = 1;
+
+ if ((scavtab[widetag] == scav_lose) ||
+ (((sizetab[widetag])(object_ptr)) > 1)) {
+ fprintf(stderr,"warning: \
+attempted to scavenge non-descriptor value %x at %p.\n\n\
+If you can reproduce this warning, please send a bug report\n\
+(see manual page for details).\n",
+ object, object_ptr);
}
}
#endif
(scavtab[widetag_of(object)])(object_ptr, object);
}
}
- gc_assert(object_ptr == end);
+ gc_assert_verbose(object_ptr == end, "Final object pointer %p, start %p, end %p\n",
+ object_ptr, start, end);
}
static lispobj trans_fun_header(lispobj object); /* forward decls */
fheaderl = fheaderp->next;
prev_pointer = &nfheaderp->next;
}
+#ifdef LISP_FEATURE_GENCGC
+ /* Cheneygc doesn't need this os_flush_icache, it flushes the whole
+ spaces once when all copying is done. */
os_flush_icache((os_vm_address_t) (((long *)new_code) + nheader_words),
ncode_words * sizeof(long));
-#ifdef LISP_FEATURE_GENCGC
+
+#endif
+
+#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
gencgc_apply_code_fixups(code, new_code);
#endif
+
return new_code;
}
entry_point != NIL;
entry_point = function_ptr->next) {
- gc_assert(is_lisp_pointer(entry_point));
+ gc_assert_verbose(is_lisp_pointer(entry_point),
+ "Entry point %lx\n is not a lisp pointer.",
+ (long)entry_point);
function_ptr = (struct simple_fun *) native_pointer(entry_point);
gc_assert(widetag_of(function_ptr->header)==SIMPLE_FUN_HEADER_WIDETAG);
scavenge(&function_ptr->name, 1);
scavenge(&function_ptr->arglist, 1);
scavenge(&function_ptr->type, 1);
+ scavenge(&function_ptr->xrefs, 1);
}
return n_words;
static long
scav_return_pc_header(lispobj *where, lispobj object)
{
- lose("attempted to scavenge a return PC header where=0x%08x object=0x%08x",
+ lose("attempted to scavenge a return PC header where=0x%08x object=0x%08x\n",
(unsigned long) where,
(unsigned long) object);
return 0; /* bogus return value to satisfy static type checking */
static long
scav_fun_header(lispobj *where, lispobj object)
{
- lose("attempted to scavenge a function header where=0x%08x object=0x%08x",
+ lose("attempted to scavenge a function header where=0x%08x object=0x%08x\n",
(unsigned long) where,
(unsigned long) object);
return 0; /* bogus return value to satisfy static type checking */
static lispobj
trans_immediate(lispobj object)
{
- lose("trying to transport an immediate");
+ lose("trying to transport an immediate\n");
return NIL; /* bogus return value to satisfy static type checking */
}
/* Note: on the sparc we don't have to do anything special for fdefns, */
/* 'cause the raw-addr has a function lowtag. */
-#ifndef LISP_FEATURE_SPARC
+#if !defined(LISP_FEATURE_SPARC)
static long
scav_fdefn(lispobj *where, lispobj object)
{
/* FSHOW((stderr, "scav_fdefn, function = %p, raw_addr = %p\n",
fdefn->fun, fdefn->raw_addr)); */
- if ((char *)(fdefn->fun + FUN_RAW_ADDR_OFFSET)
- == (char *)((unsigned long)(fdefn->raw_addr))) {
+ if ((char *)(fdefn->fun + FUN_RAW_ADDR_OFFSET) == fdefn->raw_addr) {
scavenge(where + 1, sizeof(struct fdefn)/sizeof(lispobj) - 1);
/* Don't write unnecessarily. */
gc_assert(widetag_of(wp->header)==WEAK_POINTER_WIDETAG);
/* Push the weak pointer onto the list of weak pointers. */
- wp->next = LOW_WORD(weak_pointers);
+ wp->next = (struct weak_pointer *)LOW_WORD(weak_pointers);
weak_pointers = wp;
#endif
return copy;
void scan_weak_pointers(void)
{
- struct weak_pointer *wp;
- for (wp = weak_pointers; wp != NULL; wp=wp->next) {
+ struct weak_pointer *wp, *next_wp;
+ for (wp = weak_pointers, next_wp = NULL; wp != NULL; wp = next_wp) {
lispobj value = wp->value;
lispobj *first_pointer;
gc_assert(widetag_of(wp->header)==WEAK_POINTER_WIDETAG);
+
+ next_wp = wp->next;
+ wp->next = NULL;
+ if (next_wp == wp) /* gencgc uses a ref to self for end of list */
+ next_wp = NULL;
+
if (!(is_lisp_pointer(value) && from_space_p(value)))
continue;
}
}
+\f
+/* Hash tables */
+
+#if N_WORD_BITS == 32
+#define EQ_HASH_MASK 0x1fffffff
+#elif N_WORD_BITS == 64
+#define EQ_HASH_MASK 0x1fffffffffffffff
+#endif
+
+/* Compute the EQ-hash of KEY. This must match POINTER-HASH in
+ * target-hash-table.lisp. */
+#define EQ_HASH(key) ((key) & EQ_HASH_MASK)
+
+/* List of weak hash tables chained through their NEXT-WEAK-HASH-TABLE
+ * slot. Set to NULL at the end of a collection.
+ *
+ * This is not optimal because, when a table is tenured, it won't be
+ * processed automatically; only the yougest generation is GC'd by
+ * default. On the other hand, all applications will need an
+ * occasional full GC anyway, so it's not that bad either. */
+struct hash_table *weak_hash_tables = NULL;
+
+/* Return true if OBJ has already survived the current GC. */
+static inline int
+survived_gc_yet (lispobj obj)
+{
+ return (!is_lisp_pointer(obj) || !from_space_p(obj) ||
+ forwarding_pointer_p(native_pointer(obj)));
+}
+
+static inline int
+weak_hash_entry_alivep (lispobj weakness, lispobj key, lispobj value)
+{
+ switch (weakness) {
+ case KEY:
+ return survived_gc_yet(key);
+ case VALUE:
+ return survived_gc_yet(value);
+ case KEY_OR_VALUE:
+ return (survived_gc_yet(key) || survived_gc_yet(value));
+ case KEY_AND_VALUE:
+ return (survived_gc_yet(key) && survived_gc_yet(value));
+ default:
+ gc_assert(0);
+ /* Shut compiler up. */
+ return 0;
+ }
+}
+
+/* Return the beginning of data in ARRAY (skipping the header and the
+ * length) or NULL if it isn't an array of the specified widetag after
+ * all. */
+static inline lispobj *
+get_array_data (lispobj array, int widetag, unsigned long *length)
+{
+ if (is_lisp_pointer(array) &&
+ (widetag_of(*(lispobj *)native_pointer(array)) == widetag)) {
+ if (length != NULL)
+ *length = fixnum_value(((lispobj *)native_pointer(array))[1]);
+ return ((lispobj *)native_pointer(array)) + 2;
+ } else {
+ return NULL;
+ }
+}
+
+/* Only need to worry about scavenging the _real_ entries in the
+ * table. Phantom entries such as the hash table itself at index 0 and
+ * the empty marker at index 1 were scavenged by scav_vector that
+ * either called this function directly or arranged for it to be
+ * called later by pushing the hash table onto weak_hash_tables. */
+static void
+scav_hash_table_entries (struct hash_table *hash_table)
+{
+ lispobj *kv_vector;
+ unsigned long kv_length;
+ lispobj *index_vector;
+ unsigned long length;
+ lispobj *next_vector;
+ unsigned long next_vector_length;
+ lispobj *hash_vector;
+ unsigned long hash_vector_length;
+ lispobj empty_symbol;
+ lispobj weakness = hash_table->weakness;
+ unsigned long i;
+
+ kv_vector = get_array_data(hash_table->table,
+ SIMPLE_VECTOR_WIDETAG, &kv_length);
+ if (kv_vector == NULL)
+ lose("invalid kv_vector %x\n", hash_table->table);
+
+ index_vector = get_array_data(hash_table->index_vector,
+ SIMPLE_ARRAY_WORD_WIDETAG, &length);
+ if (index_vector == NULL)
+ lose("invalid index_vector %x\n", hash_table->index_vector);
+
+ next_vector = get_array_data(hash_table->next_vector,
+ SIMPLE_ARRAY_WORD_WIDETAG,
+ &next_vector_length);
+ if (next_vector == NULL)
+ lose("invalid next_vector %x\n", hash_table->next_vector);
+
+ hash_vector = get_array_data(hash_table->hash_vector,
+ SIMPLE_ARRAY_WORD_WIDETAG,
+ &hash_vector_length);
+ if (hash_vector != NULL)
+ gc_assert(hash_vector_length == next_vector_length);
+
+ /* 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);
+
+ empty_symbol = kv_vector[1];
+ /* 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));
+ }
+
+ /* Work through the KV vector. */
+ for (i = 1; i < next_vector_length; i++) {
+ lispobj old_key = kv_vector[2*i];
+ lispobj value = kv_vector[2*i+1];
+ if ((weakness == NIL) ||
+ weak_hash_entry_alivep(weakness, old_key, value)) {
+
+ /* Scavenge the key and value. */
+ scavenge(&kv_vector[2*i],2);
+
+ /* If an EQ-based key has moved, mark the hash-table for
+ * rehashing. */
+ if (!hash_vector || hash_vector[i] == MAGIC_HASH_VECTOR_VALUE) {
+ lispobj new_key = kv_vector[2*i];
+
+ if (old_key != new_key && new_key != empty_symbol) {
+ hash_table->needs_rehash_p = T;
+ }
+ }
+ }
+ }
+}
+
+long
+scav_vector (lispobj *where, lispobj object)
+{
+ unsigned long kv_length;
+ lispobj *kv_vector;
+ struct hash_table *hash_table;
+
+ /* SB-VM:VECTOR-VALID-HASHING-SUBTYPE is set for EQ-based and weak
+ * hash tables in the Lisp HASH-TABLE code to indicate need for
+ * special GC support. */
+ if (HeaderValue(object) == subtype_VectorNormal)
+ return 1;
+
+ kv_length = fixnum_value(where[1]);
+ kv_vector = where + 2; /* Skip the header and length. */
+ /*FSHOW((stderr,"/kv_length = %d\n", kv_length));*/
+
+ /* Scavenge element 0, which may be a hash-table structure. */
+ scavenge(where+2, 1);
+ if (!is_lisp_pointer(where[2])) {
+ /* This'll happen when REHASH clears the header of old-kv-vector
+ * and fills it with zero, but some other thread simulatenously
+ * sets the header in %%PUTHASH.
+ */
+ fprintf(stderr,
+ "Warning: no pointer at %lx in hash table: this indicates "
+ "non-fatal corruption caused by concurrent access to a "
+ "hash-table from multiple threads. Any accesses to "
+ "hash-tables shared between threads should be protected "
+ "by locks.\n", (unsigned long)&where[2]);
+ // We've scavenged three words.
+ return 3;
+ }
+ 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);
+ }
+
+ /* 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]);
+ }
+
+ /* 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 (hash_table->weakness == NIL) {
+ scav_hash_table_entries(hash_table);
+ } else {
+ /* Delay scavenging of this table by pushing it onto
+ * weak_hash_tables (if it's not there already) for the weak
+ * object phase. */
+ if (hash_table->next_weak_hash_table == NIL) {
+ hash_table->next_weak_hash_table = (lispobj)weak_hash_tables;
+ weak_hash_tables = hash_table;
+ }
+ }
+
+ return (CEILING(kv_length + 2, 2));
+}
+
+void
+scav_weak_hash_tables (void)
+{
+ struct hash_table *table;
+
+ /* Scavenge entries whose triggers are known to survive. */
+ for (table = weak_hash_tables; table != NULL;
+ table = (struct hash_table *)table->next_weak_hash_table) {
+ scav_hash_table_entries(table);
+ }
+}
+
+/* Walk through the chain whose first element is *FIRST and remove
+ * dead weak entries. */
+static inline void
+scan_weak_hash_table_chain (struct hash_table *hash_table, lispobj *prev,
+ lispobj *kv_vector, lispobj *index_vector,
+ lispobj *next_vector, lispobj *hash_vector,
+ lispobj empty_symbol, lispobj weakness)
+{
+ unsigned index = *prev;
+ while (index) {
+ unsigned next = next_vector[index];
+ lispobj key = kv_vector[2 * index];
+ lispobj value = kv_vector[2 * index + 1];
+ gc_assert(key != empty_symbol);
+ gc_assert(value != empty_symbol);
+ if (!weak_hash_entry_alivep(weakness, key, value)) {
+ unsigned count = fixnum_value(hash_table->number_entries);
+ gc_assert(count > 0);
+ *prev = next;
+ hash_table->number_entries = make_fixnum(count - 1);
+ next_vector[index] = fixnum_value(hash_table->next_free_kv);
+ hash_table->next_free_kv = make_fixnum(index);
+ kv_vector[2 * index] = empty_symbol;
+ kv_vector[2 * index + 1] = empty_symbol;
+ if (hash_vector)
+ hash_vector[index] = MAGIC_HASH_VECTOR_VALUE;
+ } else {
+ prev = &next_vector[index];
+ }
+ index = next;
+ }
+}
+
+static void
+scan_weak_hash_table (struct hash_table *hash_table)
+{
+ lispobj *kv_vector;
+ lispobj *index_vector;
+ unsigned long length = 0; /* prevent warning */
+ lispobj *next_vector;
+ unsigned long next_vector_length = 0; /* prevent warning */
+ lispobj *hash_vector;
+ lispobj empty_symbol;
+ lispobj weakness = hash_table->weakness;
+ unsigned long i;
+
+ kv_vector = get_array_data(hash_table->table,
+ SIMPLE_VECTOR_WIDETAG, NULL);
+ index_vector = get_array_data(hash_table->index_vector,
+ SIMPLE_ARRAY_WORD_WIDETAG, &length);
+ next_vector = get_array_data(hash_table->next_vector,
+ SIMPLE_ARRAY_WORD_WIDETAG,
+ &next_vector_length);
+ hash_vector = get_array_data(hash_table->hash_vector,
+ SIMPLE_ARRAY_WORD_WIDETAG, NULL);
+ empty_symbol = kv_vector[1];
+
+ for (i = 0; i < length; i++) {
+ scan_weak_hash_table_chain(hash_table, &index_vector[i],
+ kv_vector, index_vector, next_vector,
+ hash_vector, empty_symbol, weakness);
+ }
+}
+
+/* Remove dead entries from weak hash tables. */
+void
+scan_weak_hash_tables (void)
+{
+ struct hash_table *table, *next;
+
+ for (table = weak_hash_tables; table != NULL; table = next) {
+ next = (struct hash_table *)table->next_weak_hash_table;
+ table->next_weak_hash_table = NIL;
+ scan_weak_hash_table(table);
+ }
+
+ weak_hash_tables = NULL;
+}
\f
/*
static long
scav_lose(lispobj *where, lispobj object)
{
- lose("no scavenge function for object 0x%08x (widetag 0x%x)",
+ lose("no scavenge function for object 0x%08x (widetag 0x%x)\n",
(unsigned long)object,
widetag_of(*(lispobj*)native_pointer(object)));
static lispobj
trans_lose(lispobj object)
{
- lose("no transport function for object 0x%08x (widetag 0x%x)",
+ lose("no transport function for object 0x%08x (widetag 0x%x)\n",
(unsigned long)object,
widetag_of(*(lispobj*)native_pointer(object)));
return NIL; /* bogus return value to satisfy static type checking */
static long
size_lose(lispobj *where)
{
- lose("no size function for object at 0x%08x (widetag 0x%x)",
+ lose("no size function for object at 0x%08x (widetag 0x%x)\n",
(unsigned long)where,
widetag_of(LOW_WORD(where)));
return 1; /* bogus return value to satisfy static type checking */
void
gc_init_tables(void)
{
- long i;
+ unsigned long i;
/* Set default value in all slots of scavenge table. FIXME
* replace this gnarly sizeof with something based on
/* skipping OTHER_IMMEDIATE_0_LOWTAG */
scavtab[LIST_POINTER_LOWTAG|(i<<N_LOWTAG_BITS)] = scav_list_pointer;
scavtab[ODD_FIXNUM_LOWTAG|(i<<N_LOWTAG_BITS)] = scav_immediate;
- scavtab[INSTANCE_POINTER_LOWTAG|(i<<N_LOWTAG_BITS)] = scav_instance_pointer;
+ scavtab[INSTANCE_POINTER_LOWTAG|(i<<N_LOWTAG_BITS)] =
+ scav_instance_pointer;
/* skipping OTHER_IMMEDIATE_1_LOWTAG */
scavtab[OTHER_POINTER_LOWTAG|(i<<N_LOWTAG_BITS)] = scav_other_pointer;
}
scavtab[COMPLEX_VECTOR_WIDETAG] = scav_boxed;
scavtab[COMPLEX_ARRAY_WIDETAG] = scav_boxed;
scavtab[CODE_HEADER_WIDETAG] = scav_code_header;
-#ifndef LISP_FEATURE_GENCGC /* FIXME ..._X86 ? */
+#if !defined(LISP_FEATURE_X86) && !defined(LISP_FEATURE_X86_64)
scavtab[SIMPLE_FUN_HEADER_WIDETAG] = scav_fun_header;
scavtab[RETURN_PC_HEADER_WIDETAG] = scav_return_pc_header;
#endif
+ scavtab[FUNCALLABLE_INSTANCE_HEADER_WIDETAG] = scav_boxed;
#if defined(LISP_FEATURE_X86) || defined(LISP_FEATURE_X86_64)
scavtab[CLOSURE_HEADER_WIDETAG] = scav_closure_header;
- scavtab[FUNCALLABLE_INSTANCE_HEADER_WIDETAG] = scav_closure_header;
#else
scavtab[CLOSURE_HEADER_WIDETAG] = scav_boxed;
- scavtab[FUNCALLABLE_INSTANCE_HEADER_WIDETAG] = scav_boxed;
#endif
scavtab[VALUE_CELL_HEADER_WIDETAG] = scav_boxed;
scavtab[SYMBOL_HEADER_WIDETAG] = scav_boxed;
scavtab[UNBOUND_MARKER_WIDETAG] = scav_immediate;
scavtab[NO_TLS_VALUE_MARKER_WIDETAG] = scav_immediate;
scavtab[INSTANCE_HEADER_WIDETAG] = scav_instance;
-#ifdef LISP_FEATURE_SPARC
+#if defined(LISP_FEATURE_SPARC)
scavtab[FDEFN_WIDETAG] = scav_boxed;
#else
scavtab[FDEFN_WIDETAG] = scav_fdefn;
#endif
+ scavtab[SIMPLE_VECTOR_WIDETAG] = scav_vector;
/* transport other table, initialized same way as scavtab */
for (i = 0; i < ((sizeof transother)/(sizeof transother[0])); i++)
lispobj thing = *start;
/* If thing is an immediate then this is a cons. */
- if (is_lisp_pointer(thing)
- || (fixnump(thing))
- || (widetag_of(thing) == CHARACTER_WIDETAG)
-#if N_WORD_BITS == 64
- || (widetag_of(thing) == SINGLE_FLOAT_WIDETAG)
-#endif
- || (widetag_of(thing) == UNBOUND_MARKER_WIDETAG))
+ if (is_lisp_pointer(thing) || is_lisp_immediate(thing))
count = 2;
else
count = (sizetab[widetag_of(thing)])(start);
}
return (NULL);
}
+
+boolean
+maybe_gc(os_context_t *context)
+{
+#ifndef LISP_FEATURE_WIN32
+ struct thread *thread = arch_os_get_current_thread();
+#endif
+
+ fake_foreign_function_call(context);
+ /* SUB-GC may return without GCing if *GC-INHIBIT* is set, in
+ * which case we will be running with no gc trigger barrier
+ * thing for a while. But it shouldn't be long until the end
+ * of WITHOUT-GCING.
+ *
+ * FIXME: It would be good to protect the end of dynamic space for
+ * CheneyGC and signal a storage condition from there.
+ */
+
+ /* Restore the signal mask from the interrupted context before
+ * calling into Lisp if interrupts are enabled. Why not always?
+ *
+ * Suppose there is a WITHOUT-INTERRUPTS block far, far out. If an
+ * interrupt hits while in SUB-GC, it is deferred and the
+ * os_context_sigmask of that interrupt is set to block further
+ * deferrable interrupts (until the first one is
+ * handled). Unfortunately, that context refers to this place and
+ * when we return from here the signals will not be blocked.
+ *
+ * A kludgy alternative is to propagate the sigmask change to the
+ * outer context.
+ */
+#ifndef LISP_FEATURE_WIN32
+ if(SymbolValue(INTERRUPTS_ENABLED,thread)!=NIL) {
+ sigset_t *context_sigmask = os_context_sigmask_addr(context);
+#ifdef LISP_FEATURE_SB_THREAD
+ /* What if the context we'd like to restore has GC signals
+ * blocked? Just skip the GC: we can't set GC_PENDING, because
+ * that would block the next attempt, and we don't know when
+ * we'd next check for it -- and it's hard to be sure that
+ * unblocking would be safe.
+ *
+ * FIXME: This is not actually much better: we may already have
+ * GC_PENDING set, and presumably our caller assumes that we will
+ * clear it. Perhaps we should, even though we don't actually GC? */
+ if (sigismember(context_sigmask,SIG_STOP_FOR_GC)) {
+ undo_fake_foreign_function_call(context);
+ return 1;
+ }
+#endif
+ thread_sigmask(SIG_SETMASK, context_sigmask, 0);
+ }
+ else
+ unblock_gc_signals();
+#endif
+ /* SIG_STOP_FOR_GC needs to be enabled before we can call lisp:
+ * otherwise two threads racing here may deadlock: the other will
+ * wait on the GC lock, and the other cannot stop the first one... */
+ funcall0(StaticSymbolFunction(SUB_GC));
+ undo_fake_foreign_function_call(context);
+ return 1;
+}