When there are multiple threads waiting for a class to
be loaded then the entry is removed from hash map and
freed by the last thread which gives up on it.
Signed-off-by: Tomek Grabiec <tgrab...@gmail.com>
---
vm/classloader.c | 83 ++++++++++++++++++++++++++++++++++++++---------------
1 files changed, 59 insertions(+), 24 deletions(-)
diff --git a/vm/classloader.c b/vm/classloader.c
index c559842..5011b3e 100644
--- a/vm/classloader.c
+++ b/vm/classloader.c
@@ -183,9 +183,18 @@ int classloader_add_to_classpath(const char *classpath)
return 0;
}
+enum class_load_status {
+ CLASS_LOADING,
+ CLASS_LOADED,
+ CLASS_NOT_FOUND,
+};
+
struct classloader_class {
- bool loaded;
+ enum class_load_status status;
struct vm_class *class;
+
+ /* number of threads waiting for a class. */
+ unsigned long nr_waiting;
};
static struct hash_map *classes;
@@ -466,6 +475,32 @@ out_filename:
return result;
}
+static struct classloader_class *find_class(const char *name)
+{
+ struct classloader_class *class;
+
+ class = lookup_class(name);
+ if (class) {
+ /*
+ * If class is being loaded by another thread then wait
+ * until loading is completed.
+ */
+
+ ++class->nr_waiting;
+ while (class->status == CLASS_LOADING)
+ pthread_cond_wait(&classloader_cond,
&classloader_mutex);
+ --class->nr_waiting;
+
+ if (class->status == CLASS_NOT_FOUND && !class->nr_waiting) {
+ hash_map_remove(classes, name);
+ free(class);
+ class = NULL;
+ }
+ }
+
+ return class;
+}
+
/* XXX: Should use hash table or tree, not linear search. -Vegard */
struct vm_class *classloader_load(const char *class_name)
{
@@ -480,24 +515,22 @@ struct vm_class *classloader_load(const char *class_name)
return NULL;
}
+ vmc = NULL;
+
pthread_mutex_lock(&classloader_mutex);
- class = lookup_class(slash_class_name);
+ class = find_class(slash_class_name);
if (class) {
- /* If class is being loaded by another thread then wait
- * until loading is completed. */
- while (!class->loaded)
- pthread_cond_wait(&classloader_cond,
&classloader_mutex);
+ if (class->status == CLASS_LOADED)
+ vmc = class->class;
- vmc = class->class;
goto out_unlock;
}
class = malloc(sizeof(*class));
- class->loaded = false;
+ class->status = CLASS_LOADING;
if (hash_map_put(classes, strdup(slash_class_name), class)) {
- NOT_IMPLEMENTED;
vmc = NULL;
goto out_unlock;
}
@@ -511,13 +544,23 @@ struct vm_class *classloader_load(const char *class_name)
*/
vmc = load_class(slash_class_name);
if (!vmc) {
+ pthread_mutex_lock(&classloader_mutex);
+
/*
- * We should remove the entry from map but other threads
- * might be waiting on it.
+ * If there are other threads waiting for class to be
+ * loaded then do not remove the entry. Last thread
+ * removes the entry.
*/
- NOT_IMPLEMENTED;
+ if (class->nr_waiting == 0) {
+ hash_map_remove(classes, slash_class_name);
+ free(class);
+ } else {
+ class->status = CLASS_NOT_FOUND;
+ pthread_cond_broadcast(&classloader_cond);
+ }
+
vmc = NULL;
- goto out;
+ goto out_unlock;
}
pthread_mutex_lock(&classloader_mutex);
@@ -525,7 +568,7 @@ struct vm_class *classloader_load(const char *class_name)
vmc->classloader = NULL;
class->class = vmc;
- class->loaded = true;
+ class->status = CLASS_LOADED;
/* Tell other threads that the class has been loaded. Would it
* be worth to use a per-class condition variable for that? */
@@ -533,8 +576,6 @@ struct vm_class *classloader_load(const char *class_name)
out_unlock:
pthread_mutex_unlock(&classloader_mutex);
-
- out:
free(slash_class_name);
trace_pop();
return vmc;
@@ -560,15 +601,9 @@ struct vm_class *classloader_find_class(const char *name)
pthread_mutex_lock(&classloader_mutex);
- class = lookup_class(slash_class_name);
- if (class) {
- /* If class is being loaded by another thread then wait
- * until loading is completed. */
- while (!class->loaded)
- pthread_cond_wait(&classloader_cond,
&classloader_mutex);
-
+ class = find_class(slash_class_name);
+ if (class && class->status == CLASS_LOADED)
vmc = class->class;
- }
free(slash_class_name);
--
1.6.0.6
------------------------------------------------------------------------------
Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day
trial. Simplify your report design, integration and deployment - and focus on
what you do best, core application coding. Discover what's new with
Crystal Reports now. http://p.sf.net/sfu/bobj-july
_______________________________________________
Jatovm-devel mailing list
Jatovm-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/jatovm-devel
