Signed-off-by: Tomek Grabiec <tgrab...@gmail.com>
---
vm/classloader.c | 94 +++++++++++++++++++++++++++++++++++++++++++----------
1 files changed, 76 insertions(+), 18 deletions(-)
diff --git a/vm/classloader.c b/vm/classloader.c
index dfc8010..a0add9d 100644
--- a/vm/classloader.c
+++ b/vm/classloader.c
@@ -12,17 +12,23 @@
#include "vm/preload.h"
#include "vm/class.h"
#include "vm/die.h"
+#include "vm/backtrace.h"
bool opt_trace_classloader;
-static int trace_classloader_level = 0;
+static __thread int trace_classloader_level = 0;
+
+static pthread_mutex_t classloader_mutex = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t classloader_cond = PTHREAD_COND_INITIALIZER;
static inline void trace_push(const char *class_name)
{
assert(trace_classloader_level >= 0);
if (opt_trace_classloader) {
+ trace_begin();
fprintf(stderr, "classloader: %*s%s\n",
trace_classloader_level, "", class_name);
+ trace_end();
}
++trace_classloader_level;
@@ -147,25 +153,39 @@ int classloader_add_to_classpath(const char *classpath)
}
struct classloader_class {
- struct vm_class *class;
+ /* If false then the class loading is in progress. */
+ bool loaded;
+
+ union {
+ /* When @loaded is false this holds the class's name. It
+ * should not be referenced when class is loaded. */
+ const char *class_name;
+
+ struct vm_class *class;
+ };
};
static struct classloader_class *classes;
static unsigned long max_classes;
static unsigned long nr_classes;
-static struct classloader_class *lookup_class(const char *class_name)
+static int lookup_class(const char *class_name)
{
unsigned long i;
for (i = 0; i < nr_classes; ++i) {
struct classloader_class *class = &classes[i];
- if (!strcmp(class->class->name, class_name))
- return class;
+ if (!class->loaded) {
+ if (!strcmp(class->class_name, class_name))
+ return i;
+ } else {
+ if (!strcmp(class->class->name, class_name))
+ return i;
+ }
}
- return NULL;
+ return -1;
}
static char *class_name_to_file_name(const char *class_name)
@@ -423,26 +443,38 @@ out_filename:
/* XXX: Should use hash table or tree, not linear search. -Vegard */
struct vm_class *classloader_load(const char *class_name)
{
- struct classloader_class *class;
struct vm_class *vmc;
struct classloader_class *new_array;
unsigned long new_max_classes;
+ int class_index;
trace_push(class_name);
- class = lookup_class(class_name);
- if (class) {
- vmc = class->class;
- goto out;
- }
+ pthread_mutex_lock(&classloader_mutex);
- vmc = load_class(class_name);
- if (!vmc) {
- NOT_IMPLEMENTED;
- vmc = NULL;
+ /*
+ * XXX: we must use index here not the entry pointer because
+ * while we're loading a class or waiting for a class to get
+ * loaded the classes array might get relocated.
+ */
+ class_index = lookup_class(class_name);
+
+ if (class_index >= 0) {
+ /* If class is being loaded by another thread then wait
+ * until loading is completed. */
+ while (!classes[class_index].loaded)
+ pthread_cond_wait(&classloader_cond,
+ &classloader_mutex);
+
+ vmc = classes[class_index].class;
goto out;
}
+ /*
+ * We allocate cache space before loading to indicate that we
+ * are loading this class and other threads wanting to load
+ * that class in the same time should wait for us.
+ */
if (nr_classes == max_classes) {
new_max_classes = 1 + max_classes * 2;
new_array = realloc(classes,
@@ -457,10 +489,36 @@ struct vm_class *classloader_load(const char *class_name)
classes = new_array;
}
- class = &classes[nr_classes++];
- class->class = vmc;
+ class_index = nr_classes++;
+
+ classes[class_index].loaded = false;
+ classes[class_index].class_name = class_name;
+
+ pthread_mutex_unlock(&classloader_mutex);
+
+ /*
+ * XXX: We cannot hold classloader_mutex lock when calling
+ * load_class() because for example vm_class_init() might call
+ * classloader_load() for superclasses.
+ */
+ vmc = load_class(class_name);
+ if (!vmc) {
+ NOT_IMPLEMENTED;
+ vmc = NULL;
+ goto out;
+ }
+
+ pthread_mutex_lock(&classloader_mutex);
+
+ classes[class_index].loaded = true;
+ classes[class_index].class = vmc;
+
+ /* Tell other threads that the class has been loaded. Would it
+ * be worth to use a per-class condition variable for that? */
+ pthread_cond_broadcast(&classloader_cond);
out:
+ pthread_mutex_unlock(&classloader_mutex);
trace_pop();
return vmc;
}
--
1.6.0.6
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