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weak-table consolidation around scm_i_register_weak_gc_callback

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* libguile/weak-table.c (GC_move_disappearing_link)
  (move_disappearing_links): Factor out stub, as in previous weak-set
  commit.
  (resize_table): As in weak-set commit, finalizers do not run within
  allocators.
  (do_vacuum_weak_table): Add comment about need for trylock.
  (scm_c_make_weak_table): Use the new scm_i_register_weak_gc_callback.
  Previously this was the case because of a mistyped check for a
  "HAVE_GC_TABLE_START_CALLBACK" symbol, whereas the symbol was actually
  HAVE_GC_SET_START_CALLBACK.  Anyway, it's better to call this after GC
  anyway, as vacuuming might need to allocate weak links (on pre-7.3
  libgc without GC_move_disappearing_link) or reallocate the backing
  vector.
This commit is contained in:
Andy Wingo 2013-01-20 12:41:15 +01:00
parent a0551390d5
commit d7cb7f7925
1 changed files with 21 additions and 72 deletions
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93
libguile/weak-table.c
View file

@ -1,4 +1,4 @@
/* Copyright (C) 2011, 2012 Free Software Foundation, Inc.
/* Copyright (C) 2011, 2012, 2013 Free Software Foundation, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
@ -151,31 +151,26 @@ unregister_disappearing_links (scm_t_weak_entry *entry,
GC_unregister_disappearing_link ((void **) &entry->value);
}
#ifndef HAVE_GC_MOVE_DISAPPEARING_LINK
static void
GC_move_disappearing_link (void **from, void **to)
{
GC_unregister_disappearing_link (from);
SCM_I_REGISTER_DISAPPEARING_LINK (to, *to);
}
#endif
static void
move_disappearing_links (scm_t_weak_entry *from, scm_t_weak_entry *to,
SCM key, SCM value, scm_t_weak_table_kind kind)
{
if ((kind == SCM_WEAK_TABLE_KIND_KEY || kind == SCM_WEAK_TABLE_KIND_BOTH)
&& SCM_HEAP_OBJECT_P (key))
{
#ifdef HAVE_GC_MOVE_DISAPPEARING_LINK
GC_move_disappearing_link ((void **) &from->key, (void **) &to->key);
#else
GC_unregister_disappearing_link ((void **) &from->key);
SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &to->key, SCM2PTR (key));
#endif
}
GC_move_disappearing_link ((void **) &from->key, (void **) &to->key);
if ((kind == SCM_WEAK_TABLE_KIND_VALUE || kind == SCM_WEAK_TABLE_KIND_BOTH)
&& SCM_HEAP_OBJECT_P (value))
{
#ifdef HAVE_GC_MOVE_DISAPPEARING_LINK
GC_move_disappearing_link ((void **) &from->value, (void **) &to->value);
#else
GC_unregister_disappearing_link ((void **) &from->value);
SCM_I_REGISTER_DISAPPEARING_LINK ((void **) &to->value, SCM2PTR (value));
#endif
}
GC_move_disappearing_link ((void **) &from->value, (void **) &to->value);
}
static void
@ -480,11 +475,7 @@ resize_table (scm_t_weak_table *table)
if (new_size_index == table->size_index)
return;
new_size = hashtable_size[new_size_index];
scm_i_pthread_mutex_unlock (&table->lock);
/* Allocating memory might cause finalizers to run, which could
run anything, so drop our lock to avoid deadlocks. */
new_entries = allocate_entries (new_size, table->kind);
scm_i_pthread_mutex_lock (&table->lock);
}
while (!is_acceptable_size_index (table, new_size_index));
@ -814,6 +805,14 @@ do_vacuum_weak_table (SCM table)
t = SCM_WEAK_TABLE (table);
/* Unlike weak sets, the weak table interface allows custom predicates
to call out to arbitrary Scheme. There are two ways that this code
can be re-entrant, then: calling weak hash procedures while in a
custom predicate, or via finalizers run explicitly by (gc) or in an
async (for non-threaded Guile). We add a restriction that
prohibits the first case, by convention. But since we can't
prohibit the second case, here we trylock instead of lock. Not so
nice. */
if (scm_i_pthread_mutex_trylock (&t->lock) == 0)
{
vacuum_weak_table (t);
@ -823,56 +822,6 @@ do_vacuum_weak_table (SCM table)
return;
}
/* The before-gc C hook only runs if GC_table_start_callback is available,
so if not, fall back on a finalizer-based implementation. */
static int
weak_gc_callback (void **weak)
{
void *val = weak[0];
void (*callback) (SCM) = weak[1];
if (!val)
return 0;
callback (SCM_PACK_POINTER (val));
return 1;
}
#ifdef HAVE_GC_TABLE_START_CALLBACK
static void*
weak_gc_hook (void *hook_data, void *fn_data, void *data)
{
if (!weak_gc_callback (fn_data))
scm_c_hook_remove (&scm_before_gc_c_hook, weak_gc_hook, fn_data);
return NULL;
}
#else
static void
weak_gc_finalizer (void *ptr, void *data)
{
if (weak_gc_callback (ptr))
scm_i_set_finalizer (ptr, weak_gc_finalizer, data);
}
#endif
static void
scm_c_register_weak_gc_callback (SCM obj, void (*callback) (SCM))
{
void **weak = GC_MALLOC_ATOMIC (sizeof (void*) * 2);
weak[0] = SCM_UNPACK_POINTER (obj);
weak[1] = (void*)callback;
GC_GENERAL_REGISTER_DISAPPEARING_LINK (weak, SCM2PTR (obj));
#ifdef HAVE_GC_TABLE_START_CALLBACK
scm_c_hook_add (&scm_after_gc_c_hook, weak_gc_hook, weak, 0);
#else
scm_i_set_finalizer (weak, weak_gc_finalizer, NULL);
#endif
}
SCM
scm_c_make_weak_table (unsigned long k, scm_t_weak_table_kind kind)
{
@ -880,7 +829,7 @@ scm_c_make_weak_table (unsigned long k, scm_t_weak_table_kind kind)
ret = make_weak_table (k, kind);
scm_c_register_weak_gc_callback (ret, do_vacuum_weak_table);
scm_i_register_weak_gc_callback (ret, do_vacuum_weak_table);
return ret;
}