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8242484: Rework thread deletion during VM termination

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Always delete JavaThread that calls Thread::destroy_vm()

Reviewed-by: dholmes, rehn, coleenp
This commit is contained in:
Patricio Chilano Mateo 2020-04-21 17:50:48 +00:00
parent efa570126b
commit d19f5f6830
3 changed files with 36 additions and 32 deletions
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28
src/hotspot/share/runtime/thread.cpp
View file

@ -4427,6 +4427,16 @@ bool Threads::destroy_vm() {
thread->exit(true);
// We are no longer on the main thread list but could still be in a
// secondary list where another thread may try to interact with us.
// So wait until all such interactions are complete before we bring
// the VM to the termination safepoint. Normally this would be done
// using thread->smr_delete() below where we delete the thread, but
// we can't call that after the termination safepoint is active as
// we will deadlock on the Threads_lock. Once all interactions are
// complete it is safe to directly delete the thread at any time.
ThreadsSMRSupport::wait_until_not_protected(thread);
// Stop VM thread.
{
// 4945125 The vm thread comes to a safepoint during exit.
@ -4466,21 +4476,9 @@ bool Threads::destroy_vm() {
// exit_globals() will delete tty
exit_globals();
// We are here after VM_Exit::set_vm_exited() so we can't call
// thread->smr_delete() or we will block on the Threads_lock. We
// must check that there are no active references to this thread
// before attempting to delete it. A thread could be waiting on
// _handshake_turn_sem trying to execute a direct handshake with
// this thread.
if (!ThreadsSMRSupport::is_a_protected_JavaThread(thread)) {
delete thread;
} else {
// Clear value for _thread_key in TLS to prevent, depending
// on pthreads implementation, possible execution of
// thread-specific destructor in infinite loop at thread
// exit.
Thread::clear_thread_current();
}
// Deleting the shutdown thread here is safe. See comment on
// wait_until_not_protected() above.
delete thread;
#if INCLUDE_JVMCI
if (JVMCICounterSize > 0) {

39
src/hotspot/share/runtime/threadSMR.cpp
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2017, 2020, 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
@ -950,14 +950,30 @@ void ThreadsSMRSupport::set_delete_notify() {
// ThreadsListHandle.
//
void ThreadsSMRSupport::smr_delete(JavaThread *thread) {
assert(!Threads_lock->owned_by_self(), "sanity");
bool has_logged_once = false;
elapsedTimer timer;
if (EnableThreadSMRStatistics) {
timer.start();
}
wait_until_not_protected(thread);
delete thread;
if (EnableThreadSMRStatistics) {
timer.stop();
uint millis = (uint)timer.milliseconds();
ThreadsSMRSupport::inc_deleted_thread_cnt();
ThreadsSMRSupport::add_deleted_thread_times(millis);
ThreadsSMRSupport::update_deleted_thread_time_max(millis);
}
log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: thread=" INTPTR_FORMAT " is deleted.", os::current_thread_id(), p2i(thread));
}
void ThreadsSMRSupport::wait_until_not_protected(JavaThread *thread) {
assert(!Threads_lock->owned_by_self(), "sanity");
bool has_logged_once = false;
while (true) {
{
// Will not make a safepoint check because this JavaThread
@ -979,14 +995,14 @@ void ThreadsSMRSupport::smr_delete(JavaThread *thread) {
}
if (!has_logged_once) {
has_logged_once = true;
log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: thread=" INTPTR_FORMAT " is not deleted.", os::current_thread_id(), p2i(thread));
log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::wait_until_not_protected: thread=" INTPTR_FORMAT " is not deleted.", os::current_thread_id(), p2i(thread));
if (log_is_enabled(Debug, os, thread)) {
ScanHazardPtrPrintMatchingThreadsClosure scan_cl(thread);
threads_do(&scan_cl);
ThreadsList* current = _to_delete_list;
while (current != NULL) {
if (current->_nested_handle_cnt != 0 && current->includes(thread)) {
log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: found nested hazard pointer to thread=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread));
log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::wait_until_not_protected: found nested hazard pointer to thread=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread));
}
current = current->next_list();
}
@ -1012,17 +1028,6 @@ void ThreadsSMRSupport::smr_delete(JavaThread *thread) {
ThreadsSMRSupport::delete_lock()->unlock();
// Retry the whole scenario.
}
delete thread;
if (EnableThreadSMRStatistics) {
timer.stop();
uint millis = (uint)timer.milliseconds();
ThreadsSMRSupport::inc_deleted_thread_cnt();
ThreadsSMRSupport::add_deleted_thread_times(millis);
ThreadsSMRSupport::update_deleted_thread_time_max(millis);
}
log_debug(thread, smr)("tid=" UINTX_FORMAT ": ThreadsSMRSupport::smr_delete: thread=" INTPTR_FORMAT " is deleted.", os::current_thread_id(), p2i(thread));
}
// Apply the closure to all threads in the system, with a snapshot of

1
src/hotspot/share/runtime/threadSMR.hpp
View file

@ -144,6 +144,7 @@ class ThreadsSMRSupport : AllStatic {
static ThreadsList* get_java_thread_list();
static bool is_a_protected_JavaThread(JavaThread *thread);
static bool is_a_protected_JavaThread_with_lock(JavaThread *thread);
static void wait_until_not_protected(JavaThread *thread);
static bool is_bootstrap_list(ThreadsList* list);
static void remove_thread(JavaThread *thread);
static void smr_delete(JavaThread *thread);