[bug #24867] `define' should be thread-safe

[Linas Vepstas <INVALID.NOREPLY@gnu.org>]

Follow-up Comment #2, bug #24867 (project guile):


The following patch protects the update of the module hash tables
to be thread-safe. This is a partial solution to the bug reported 
in https://savannah.gnu.org/bugs/?24867 This is not a full solution,
because other threads might still be reading the hash tables while
they are being updated, and thus may obtain stale/bad data.

Signed-off-by: Linas Vepstas <linasvepstas@gmail.com>

---
 libguile/modules.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Index: guile-1.8.6/libguile/modules.c
===================================================================
--- guile-1.8.6.orig/libguile/modules.c	2008-12-22 18:38:41.000000000 -0600
+++ guile-1.8.6/libguile/modules.c	2008-12-22 20:22:19.000000000 -0600
@@ -555,11 +555,16 @@ scm_c_define (const char *name, SCM valu
   return scm_define (scm_from_locale_symbol (name), value);
 }
 
+scm_i_pthread_mutex_t scm_i_define_mutex;
+
 SCM
 scm_define (SCM sym, SCM value)
 {
-  SCM var =
+  SCM var;
+  scm_pthread_mutex_lock(&scm_i_define_mutex);
+  var =
     scm_sym2var (sym, scm_current_module_lookup_closure (), SCM_BOOL_T);
+  scm_i_pthread_mutex_unlock(&scm_i_define_mutex);
   SCM_VARIABLE_SET (var, value);
   return var;
 }
@@ -651,6 +656,8 @@ void
 scm_init_modules ()
 {
 #include "libguile/modules.x"
+  scm_i_pthread_mutex_init (&scm_i_define_mutex, NULL);
+
   module_make_local_var_x_var = scm_c_define ("module-make-local-var!",
 					    SCM_UNDEFINED);
   scm_tc16_eval_closure = scm_make_smob_type ("eval-closure", 0);


(file #17118)
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Additional Item Attachment:

File name: define-race.patch              Size:1 KB


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