Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

8281615: Deadlock caused by jdwp agent #843

Closed
wants to merge 1 commit into from
Closed
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Jump to
Jump to file
Failed to load files.
Diff view
Diff view
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2001, 2005, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -81,14 +81,22 @@ cbTrackingObjectFree(jvmtiEnv* jvmti_env, jlong tag)
struct bag *
classTrack_processUnloads(JNIEnv *env)
{
debugMonitorEnter(classTrackLock);
if (deletedSignatures == NULL) {
// Class tracking not initialized, nobody's interested.
debugMonitorExit(classTrackLock);
return NULL;
return NULL;
}

/* Allocate new bag outside classTrackLock lock to avoid deadlock.
*
* Note: jvmtiAllocate/jvmtiDeallocate() may be blocked by ongoing safepoints.
* It is dangerous to call them (via bagCreateBag/bagDestroyBag()) while holding monitor(s),
* because jvmti may post events, e.g. JVMTI_EVENT_OBJECT_FREE at safepoints and event processing
* code may acquire the same monitor(s), e.g. classTrackLock in cbTrackingObjectFree(),
* which can lead to deadlock.
*/
struct bag* new_bag = bagCreateBag(sizeof(char*), 10);
debugMonitorEnter(classTrackLock);
struct bag* deleted = deletedSignatures;
deletedSignatures = bagCreateBag(sizeof(char*), 10);
deletedSignatures = new_bag;
debugMonitorExit(classTrackLock);
return deleted;
}
@@ -194,8 +202,11 @@ classTrack_initialize(JNIEnv *env)
void
classTrack_activate(JNIEnv *env)
{
// Allocate bag outside classTrackLock lock to avoid deadlock.
// See comments in classTrack_processUnloads() for details.
struct bag* new_bag = bagCreateBag(sizeof(char*), 1000);
debugMonitorEnter(classTrackLock);
deletedSignatures = bagCreateBag(sizeof(char*), 1000);
deletedSignatures = new_bag;
debugMonitorExit(classTrackLock);
}

@@ -214,12 +225,14 @@ void
classTrack_reset(void)
{
debugMonitorEnter(classTrackLock);
struct bag* to_delete = deletedSignatures;
deletedSignatures = NULL;
debugMonitorExit(classTrackLock);

if (deletedSignatures != NULL) {
bagEnumerateOver(deletedSignatures, cleanDeleted, NULL);
bagDestroyBag(deletedSignatures);
deletedSignatures = NULL;
// Deallocate bag outside classTrackLock to avoid deadlock.
// See comments in classTrack_processUnloads() for details.
if (to_delete != NULL) {
bagEnumerateOver(to_delete, cleanDeleted, NULL);
bagDestroyBag(to_delete);
}

debugMonitorExit(classTrackLock);
}