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8369991: Thread blocking during JFR emergency dump must be in safepoint safe state #27862

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8369991: Thread blocking during JFR emergency dump must be in safepoint safe state #27862

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8369991
mgronlun Oct 16, 2025
c4295b8
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mgronlun Oct 17, 2025
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13 changes: 9 additions & 4 deletions src/hotspot/share/jfr/recorder/repository/jfrEmergencyDump.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -458,6 +458,7 @@ const char* JfrEmergencyDump::chunk_path(const char* repository_path) {
*/
static void release_locks(Thread* thread) {
assert(thread != nullptr, "invariant");
assert(!thread->is_Java_thread() || JavaThread::cast(thread)->thread_state() == _thread_in_vm, "invariant");

#ifdef ASSERT
Mutex* owned_lock = thread->owned_locks();
Expand Down Expand Up @@ -519,13 +520,14 @@ static void release_locks(Thread* thread) {

class JavaThreadInVMAndNative : public StackObj {
private:
JavaThread* const _jt;
JavaThread* _jt;
JavaThreadState _original_state;
public:

JavaThreadInVMAndNative(Thread* t) : _jt(t->is_Java_thread() ? JavaThread::cast(t) : nullptr),
JavaThreadInVMAndNative(Thread* t) : _jt(nullptr),
_original_state(_thread_max_state) {
if (_jt != nullptr) {
if (t != nullptr && t->is_Java_thread()) {
_jt = JavaThread::cast(t);
_original_state = _jt->thread_state();
if (_original_state != _thread_in_vm) {
_jt->set_thread_state(_thread_in_vm);
Expand All @@ -535,6 +537,7 @@ class JavaThreadInVMAndNative : public StackObj {

~JavaThreadInVMAndNative() {
if (_original_state != _thread_max_state) {
assert(_jt != nullptr, "invariant");
_jt->set_thread_state(_original_state);
}
}
Expand Down Expand Up @@ -574,11 +577,13 @@ static bool guard_reentrancy() {
Thread* const thread = Thread::current_or_null_safe();
const traceid tid = thread != nullptr ? JFR_JVM_THREAD_ID(thread) : max_julong;
if (AtomicAccess::cmpxchg(&_jfr_shutdown_tid, shutdown_tid, tid) != shutdown_tid) {
JavaThreadInVMAndNative jtivm(thread);
if (thread != nullptr) {
JavaThreadInVMAndNative jtivm(thread);
release_locks(thread);
}
log_info(jfr, system)("A jfr emergency dump is already in progress, waiting for thread id " UINT64_FORMAT_X, AtomicAccess::load(&_jfr_shutdown_tid));
// Transition to a safe safepoint state for the infinite sleep. A nop for non-java threads.
jtivm.transition_to_native();
os::infinite_sleep(); // stay here until we exit normally or crash.
ShouldNotReachHere();
}
Expand Down