-/* Copyright (C) 2012, 2014 Free Software Foundation, Inc.
+/* Copyright (C) 2012, 2013, 2014 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
# include <config.h>
#endif
+#include <unistd.h>
+#include <fcntl.h>
+
+#include <full-write.h>
+
#include "libguile/bdw-gc.h"
#include "libguile/_scm.h"
#include "libguile/finalizers.h"
\f
-#ifndef HAVE_GC_SET_FINALIZER_NOTIFIER
+#if SCM_USE_PTHREAD_THREADS
+
+static int finalization_pipe[2];
+static scm_i_pthread_mutex_t finalization_thread_lock =
+ SCM_I_PTHREAD_MUTEX_INITIALIZER;
+static pthread_t finalization_thread;
+static int finalization_thread_is_running = 0;
+
static void
-GC_set_finalizer_notifier (void (*notifier) (void))
+notify_finalizers_to_run (void)
{
- GC_finalizer_notifier = notifier;
+ char byte = 0;
+ full_write (finalization_pipe[1], &byte, 1);
}
+
+static void
+notify_about_to_fork (void)
+{
+ char byte = 1;
+ full_write (finalization_pipe[1], &byte, 1);
+}
+
+struct finalization_pipe_data
+{
+ char byte;
+ ssize_t n;
+ int err;
+};
+
+static void*
+read_finalization_pipe_data (void *data)
+{
+ struct finalization_pipe_data *fdata = data;
+
+ fdata->n = read (finalization_pipe[0], &fdata->byte, 1);
+ fdata->err = errno;
+
+ return NULL;
+}
+
+static void*
+finalization_thread_proc (void *unused)
+{
+ while (1)
+ {
+ struct finalization_pipe_data data;
+
+ scm_without_guile (read_finalization_pipe_data, &data);
+
+ if (data.n <= 0 && data.err != EINTR)
+ {
+ perror ("error in finalization thread");
+ return NULL;
+ }
+
+ switch (data.byte)
+ {
+ case 0:
+ scm_run_finalizers ();
+ break;
+ case 1:
+ return NULL;
+ default:
+ abort ();
+ }
+ }
+}
+
+static void*
+run_finalization_thread (void *arg)
+{
+ return scm_with_guile (finalization_thread_proc, arg);
+}
+
+static void
+start_finalization_thread (void)
+{
+ scm_i_pthread_mutex_lock (&finalization_thread_lock);
+ if (!finalization_thread_is_running)
+ {
+ /* Use the raw pthread API and scm_with_guile, because we don't want
+ to block on any lock that scm_spawn_thread might want to take,
+ and we don't want to inherit the dynamic state (fluids) of the
+ caller. */
+ if (pthread_create (&finalization_thread, NULL,
+ run_finalization_thread, NULL))
+ perror ("error creating finalization thread");
+ else
+ finalization_thread_is_running = 1;
+ }
+ scm_i_pthread_mutex_unlock (&finalization_thread_lock);
+}
+
+static void
+stop_finalization_thread (void)
+{
+ scm_i_pthread_mutex_lock (&finalization_thread_lock);
+ if (finalization_thread_is_running)
+ {
+ notify_about_to_fork ();
+ if (pthread_join (finalization_thread, NULL))
+ perror ("joining finalization thread");
+ finalization_thread_is_running = 0;
+ }
+ scm_i_pthread_mutex_unlock (&finalization_thread_lock);
+}
+
+static void
+spawn_finalizer_thread (void)
+{
+ GC_set_finalizer_notifier (notify_finalizers_to_run);
+ start_finalization_thread ();
+}
+
+#endif /* SCM_USE_PTHREAD_THREADS */
+
+
+\f
+
+void
+scm_i_finalizer_pre_fork (void)
+{
+#if SCM_USE_PTHREAD_THREADS
+ if (automatic_finalization_p)
+ {
+ stop_finalization_thread ();
+ GC_set_finalizer_notifier (spawn_finalizer_thread);
+ }
#endif
+}
\f
+static void*
+weak_pointer_ref (void *weak_pointer)
+{
+ return *(void **) weak_pointer;
+}
+
+static void
+weak_gc_finalizer (void *ptr, void *data)
+{
+ void **weak = ptr;
+ void *val;
+ void (*callback) (SCM) = weak[1];
+
+ val = GC_call_with_alloc_lock (weak_pointer_ref, &weak[0]);
+
+ if (!val)
+ return;
+
+ callback (SCM_PACK_POINTER (val));
+
+ scm_i_set_finalizer (ptr, weak_gc_finalizer, data);
+}
+
+/* CALLBACK will be called on OBJ, as long as OBJ is accessible. It
+ will be called from a finalizer, which may be from an async or from
+ another thread.
+
+ As an implementation detail, the way this works is that we allocate
+ a fresh pointer-less object holding two words. We know that this
+ object should get collected the next time GC is run, so we attach a
+ finalizer to it so that we get a callback after GC happens.
+
+ The first word of the object holds a weak reference to OBJ, and the
+ second holds the callback pointer. When the callback is called, we
+ check if the weak reference on OBJ still holds. If it doesn't hold,
+ then OBJ is no longer accessible, and we're done. Otherwise we call
+ the callback and re-register a finalizer for our two-word GC object,
+ effectively resuscitating the object so that we will get a callback
+ on the next GC.
+
+ We could use the scm_after_gc_hook, but using a finalizer has the
+ advantage of potentially running in another thread, decreasing pause
+ time. */
+void
+scm_i_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));
+
+ scm_i_set_finalizer (weak, weak_gc_finalizer, NULL);
+}
+
+
int
scm_set_automatic_finalization_enabled (int enabled_p)
{
return was_enabled_p;
}
- GC_set_finalizer_notifier (enabled_p ? queue_finalizer_async : 0);
+ if (enabled_p)
+ {
+#if SCM_USE_PTHREAD_THREADS
+ if (pipe2 (finalization_pipe, O_CLOEXEC) != 0)
+ scm_syserror (NULL);
+ GC_set_finalizer_notifier (spawn_finalizer_thread);
+#else
+ GC_set_finalizer_notifier (queue_finalizer_async);
+#endif
+ }
+ else
+ {
+ GC_set_finalizer_notifier (0);
+
+#if SCM_USE_PTHREAD_THREADS
+ stop_finalization_thread ();
+ close (finalization_pipe[0]);
+ close (finalization_pipe[1]);
+ finalization_pipe[0] = -1;
+ finalization_pipe[1] = -1;
+#endif
+ }
automatic_finalization_p = enabled_p;
if (automatic_finalization_p)
GC_set_finalizer_notifier (queue_finalizer_async);
}
+
+void
+scm_init_finalizer_thread (void)
+{
+#if SCM_USE_PTHREAD_THREADS
+ if (automatic_finalization_p)
+ {
+ if (pipe2 (finalization_pipe, O_CLOEXEC) != 0)
+ scm_syserror (NULL);
+ GC_set_finalizer_notifier (spawn_finalizer_thread);
+ }
+#endif
+}
HCoop / bpt / guile.git / blobdiff