Skip to content
Permalink
Browse files
8281615: Deadlock caused by jdwp agent
Backport-of: e1060bee2adb9f2e07ca09309d0f89132db30f28
  • Loading branch information
zhengyu123 committed Mar 15, 2022
1 parent 507cbd6 commit defa9e8c83e0262d5735042e087720787f18ccaf
Showing 1 changed file with 26 additions and 13 deletions.
@@ -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);
}

1 comment on commit defa9e8

@openjdk-notifier
Copy link

@openjdk-notifier openjdk-notifier bot commented on defa9e8 Mar 15, 2022

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Please sign in to comment.