diff options
author | Andy Wingo <wingo@pobox.com> | 2014-04-17 15:29:13 +0200 |
---|---|---|
committer | Andy Wingo <wingo@pobox.com> | 2014-04-26 14:46:45 +0200 |
commit | fa1a30726dc28c58cb01594ae6df27e80d4c2f00 (patch) | |
tree | ab8f16a7d36b110a0cc8cc04b8384c4f816ea31f | |
parent | e0da53b4fe4abee2cdcd97fe46eeefcaab1da631 (diff) | |
download | guile-fa1a30726dc28c58cb01594ae6df27e80d4c2f00.tar.gz |
Add interface to disable automatic finalization
* libguile/finalizers.h:
* libguile/finalizers.c (run_finalizers_async_thunk): Call the new
scm_run_finalizers helper.
(scm_set_automatic_finalization_enabled, scm_run_finalizers): New
functions.
(scm_init_finalizers): Only set a finalizer notifier if automatic
finalization is enabled.
* doc/ref/libguile-smobs.texi (Garbage Collecting Smobs): Add discussion
of concurrency.
* doc/ref/api-smobs.texi (Smobs): Document new functions.
-rw-r--r-- | doc/ref/api-smobs.texi | 32 | ||||
-rw-r--r-- | doc/ref/libguile-smobs.texi | 23 | ||||
-rw-r--r-- | libguile/finalizers.c | 47 | ||||
-rw-r--r-- | libguile/finalizers.h | 5 |
4 files changed, 101 insertions, 6 deletions
diff --git a/doc/ref/api-smobs.texi b/doc/ref/api-smobs.texi index 345bf7cbd..cfabd3988 100644 --- a/doc/ref/api-smobs.texi +++ b/doc/ref/api-smobs.texi @@ -1,6 +1,6 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. -@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2009, 2013 +@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2009, 2013, 2014 @c Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @@ -60,6 +60,36 @@ memory is automatically reclaimed by the garbage collector when it is no longer needed (@pxref{Memory Blocks, @code{scm_gc_malloc}}). @end deftypefn +Smob free functions must be thread-safe. @xref{Garbage Collecting +Smobs}, for a discussion on finalizers and concurrency. If you are +embedding Guile in an application that is not thread-safe, and you +define smob types that need finalization, you might want to disable +automatic finalization, and arrange to call +@code{scm_manually_run_finalizers ()} yourself. + +@deftypefn {C Function} int scm_set_automatic_finalization_enabled (int enabled_p) +Enable or disable automatic finalization. By default, Guile arranges to +invoke object finalizers automatically, in a separate thread if +possible. Passing a zero value for @var{enabled_p} will disable +automatic finalization for Guile as a whole. If you disable automatic +finalization, you will have to call @code{scm_run_finalizers ()} +periodically. + +Unlike most other Guile functions, you can call +@code{scm_set_automatic_finalization_enabled} before Guile has been +initialized. + +Return the previous status of automatic finalization. +@end deftypefn + +@deftypefn {C Function} int scm_run_finalizers (void) +Invoke any pending finalizers. Returns the number of finalizers that +were invoked. This function should be called when automatic +finalization is disabled, though it may be called if it is enabled as +well. +@end deftypefn + + @cindex precise marking @deftypefn {C Function} void scm_set_smob_mark (scm_t_bits tc, SCM (*mark) (SCM obj)) diff --git a/doc/ref/libguile-smobs.texi b/doc/ref/libguile-smobs.texi index 572bcf316..f12ab1303 100644 --- a/doc/ref/libguile-smobs.texi +++ b/doc/ref/libguile-smobs.texi @@ -1,6 +1,6 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. -@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2010, 2011, 2013 +@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2010, 2011, 2013, 2014 @c Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @@ -385,6 +385,27 @@ During the sweep phase, the garbage collector will clear the mark bits on all live objects. The code which implements a smob need not do this itself. +@cindex finalizer +@cindex finalization + +Note that the free function can be called in any context. In +particular, if your Guile is built with support for threads, the +finalizer may be called from any thread that is running Guile. In Guile +2.0, finalizers are invoked via ``asyncs'', which interleaves them with +running Scheme code; @pxref{System asyncs}. In Guile 2.2 there will be +a dedicated finalization thread, to ensure that the finalization doesn't +run within the critical section of any other thread known to Guile. + +In either case, finalizers (free functions) run concurrently with the +main program, and so they need to be async-safe and thread-safe. If for +some reason this is impossible, perhaps because you are embedding Guile +in some application that is not itself thread-safe, you have a few +options. One is to use guardians instead of free functions, and arrange +to pump the guardians for finalizable objects. @xref{Guardians}, for +more information. The other option is to disable automatic finalization +entirely, and arrange to call @code{scm_run_finalizers ()} at +appropriate points. @xref{Smobs}, for more on these interfaces. + There is no way for smob code to be notified when collection is complete. diff --git a/libguile/finalizers.c b/libguile/finalizers.c index a179479f5..6abc70091 100644 --- a/libguile/finalizers.c +++ b/libguile/finalizers.c @@ -1,4 +1,4 @@ -/* Copyright (C) 2012 Free Software Foundation, Inc. +/* Copyright (C) 2012, 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 @@ -31,6 +31,8 @@ +static int automatic_finalization_p = 1; + static size_t finalization_count; @@ -130,7 +132,7 @@ static SCM finalizer_async_cell; static SCM run_finalizers_async_thunk (void) { - finalization_count += GC_invoke_finalizers (); + scm_run_finalizers (); return SCM_UNSPECIFIED; } @@ -169,6 +171,43 @@ GC_set_finalizer_notifier (void (*notifier) (void)) } #endif + + + +int +scm_set_automatic_finalization_enabled (int enabled_p) +{ + int was_enabled_p = automatic_finalization_p; + + if (enabled_p == was_enabled_p) + return was_enabled_p; + + if (!scm_initialized_p) + { + automatic_finalization_p = enabled_p; + return was_enabled_p; + } + + GC_set_finalizer_notifier (enabled_p ? queue_finalizer_async : 0); + + automatic_finalization_p = enabled_p; + + return was_enabled_p; +} + +int +scm_run_finalizers (void) +{ + int finalized = GC_invoke_finalizers (); + + finalization_count += finalized; + + return finalized; +} + + + + void scm_init_finalizers (void) { @@ -178,5 +217,7 @@ scm_init_finalizers (void) scm_cons (scm_c_make_gsubr ("%run-finalizers", 0, 0, 0, run_finalizers_async_thunk), SCM_BOOL_F); - GC_set_finalizer_notifier (queue_finalizer_async); + + if (automatic_finalization_p) + GC_set_finalizer_notifier (queue_finalizer_async); } diff --git a/libguile/finalizers.h b/libguile/finalizers.h index bad96e145..12ccbb689 100644 --- a/libguile/finalizers.h +++ b/libguile/finalizers.h @@ -1,7 +1,7 @@ #ifndef SCM_FINALIZERS_H #define SCM_FINALIZERS_H -/* Copyright (C) 2012 Free Software Foundation, Inc. +/* Copyright (C) 2012, 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 @@ -34,6 +34,9 @@ SCM_INTERNAL void scm_i_add_finalizer (void *obj, scm_t_finalizer_proc, SCM_INTERNAL void scm_i_add_resuscitator (void *obj, scm_t_finalizer_proc, void *data); +SCM_API int scm_set_automatic_finalization_enabled (int enabled_p); +SCM_API int scm_run_finalizers (void); + SCM_INTERNAL void scm_init_finalizers (void); #endif /* SCM_FINALIZERS_H */ |