Am 11.05.2011 19:41, schrieb Andi Vajda:
> If these functions eventually instantiate a Thread class, even indirectly,
> the monkey-patching may still work.
Some of the code doesn't use the threading module at all, just thread or
the internal C API. I'd have to patch the modules and C code.
> That may cover this case but what about all the others ?
> There is a reason the call has to be manual.
>
> I've not been able to automate it before.
> Over time, I've added checks where I could but I've not found it possible to
> cover all cases where attachCurrentThread() wasn't called.
>
> Anyhow, try it and see if it fixes the problem you're seeing.
> If any of the objects being freed invoke user code that eventually call into
> the JVM, the problem is going to appear again elsewhere.
I understand your reluctance to automate the attaching of Python threads
to the JVM. Explicit is better than implicit. However this is a special
case. CPython doesn't allow to control cyclic garbage collector's
threading attachment nor does CPython have a hook that is called for
newly created threads. It's hard to debug a segfault when even code like
"a = []" can trigger the bug.
The attached patch doesn't trigger the bug in my artificial test code.
I'm going to run our test suite several times. That's going to take a
while.
Christian
Index: jcc/sources/jcc.cpp
===================================================================
--- jcc/sources/jcc.cpp (Revision 1088091)
+++ jcc/sources/jcc.cpp (Arbeitskopie)
@@ -33,6 +33,25 @@
/* JCCEnv */
+int jccenv_attachCurrentThread(char *name, int asDaemon)
+{
+ int result;
+ JNIEnv *jenv = NULL;
+
+ JavaVMAttachArgs attach = {
+ JNI_VERSION_1_4, name, NULL
+ };
+
+ if (asDaemon)
+ result = env->vm->AttachCurrentThreadAsDaemon((void **) &jenv, &attach);
+ else
+ result = env->vm->AttachCurrentThread((void **) &jenv, &attach);
+
+ env->set_vm_env(jenv);
+
+ return result;
+}
+
class t_jccenv {
public:
PyObject_HEAD
@@ -154,21 +173,11 @@
{
char *name = NULL;
int asDaemon = 0, result;
- JNIEnv *jenv = NULL;
if (!PyArg_ParseTuple(args, "|si", &name, &asDaemon))
return NULL;
- JavaVMAttachArgs attach = {
- JNI_VERSION_1_4, name, NULL
- };
-
- if (asDaemon)
- result = env->vm->AttachCurrentThreadAsDaemon((void **) &jenv, &attach);
- else
- result = env->vm->AttachCurrentThread((void **) &jenv, &attach);
-
- env->set_vm_env(jenv);
+ result = jccenv_attachCurrentThread(name, asDaemon);
return PyInt_FromLong(result);
}
Index: jcc/sources/JCCEnv.cpp
===================================================================
--- jcc/sources/JCCEnv.cpp (Revision 1088091)
+++ jcc/sources/JCCEnv.cpp (Arbeitskopie)
@@ -318,6 +318,16 @@
{
if (iter->second.count == 1)
{
+ JNIEnv *vm_env = get_vm_env();
+ if (!vm_env)
+ {
+ /* Python's cyclic garbage collector may remove
+ * an object inside a thread that is not attached
+ * to the JVM. This makes sure JCC doesn't segfault.
+ */
+ jccenv_attachCurrentThread(NULL, 0);
+ vm_env = get_vm_env();
+ }
get_vm_env()->DeleteGlobalRef(iter->second.global);
refs.erase(iter);
}
Index: jcc/sources/JCCEnv.h
===================================================================
--- jcc/sources/JCCEnv.h (Revision 1088091)
+++ jcc/sources/JCCEnv.h (Arbeitskopie)
@@ -72,6 +72,8 @@
typedef jclass (*getclassfn)(void);
+int jccenv_attachCurrentThread(char *name, int asDaemon);
+
class countedRef {
public:
jobject global;
