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fix potential concurrency bugs in port-for-each

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* libguile/ports.c (scm_c_port_for_each): Simplify to avoid concurrency-
  and gc-related bugs.
This commit is contained in:
Andy Wingo 2011-02-10 21:40:25 +01:00
parent e8065fe452
commit b7b4aef97c
1 changed files with 12 additions and 27 deletions
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33
libguile/ports.c
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@ -867,44 +867,29 @@ SCM_DEFINE (scm_close_output_port, "close-output-port", 1, 0, 0,
#undef FUNC_NAME
static SCM
scm_i_collect_keys_in_vector (void *closure, SCM key, SCM value, SCM result)
collect_keys (void *unused, SCM key, SCM value, SCM result)
{
int *i = (int*) closure;
scm_c_vector_set_x (result, *i, key);
(*i)++;
return result;
return scm_cons (key, result);
}
void
scm_c_port_for_each (void (*proc)(void *data, SCM p), void *data)
{
int i = 0;
size_t n;
SCM ports;
/* Even without pre-emptive multithreading, running arbitrary code
while scanning the port table is unsafe because the port table
can change arbitrarily (from a GC, for example). So we first
collect the ports into a vector. -mvo */
scm_i_scm_pthread_mutex_lock (&scm_i_port_table_mutex);
n = SCM_HASHTABLE_N_ITEMS (scm_i_port_weak_hash);
scm_i_pthread_mutex_unlock (&scm_i_port_table_mutex);
ports = scm_c_make_vector (n, SCM_BOOL_F);
/* Copy out the port table as a list so that we get strong references
to all the values. */
scm_i_pthread_mutex_lock (&scm_i_port_table_mutex);
ports = scm_internal_hash_fold (scm_i_collect_keys_in_vector, &i,
ports, scm_i_port_weak_hash);
ports = scm_internal_hash_fold (collect_keys, NULL,
SCM_EOL, scm_i_port_weak_hash);
scm_i_pthread_mutex_unlock (&scm_i_port_table_mutex);
for (i = 0; i < n; i++) {
SCM p = SCM_SIMPLE_VECTOR_REF (ports, i);
for (; scm_is_pair (ports); ports = scm_cdr (ports))
{
SCM p = scm_car (ports);
if (SCM_PORTP (p))
proc (data, p);
}
scm_remember_upto_here_1 (ports);
}
SCM_DEFINE (scm_port_for_each, "port-for-each", 1, 0, 0,