8298377: JfrVframeStream causes deadlocks in ZGC
Backport-of: 453dbd12ee42731d7ebfd1a856338099429277c8
diff --git a/src/hotspot/share/jfr/periodic/sampling/jfrThreadSampler.cpp b/src/hotspot/share/jfr/periodic/sampling/jfrThreadSampler.cpp
index 3574471..0b31888 100644
--- a/src/hotspot/share/jfr/periodic/sampling/jfrThreadSampler.cpp
+++ b/src/hotspot/share/jfr/periodic/sampling/jfrThreadSampler.cpp
@@ -41,6 +41,7 @@
#include "runtime/javaThread.inline.hpp"
#include "runtime/os.hpp"
#include "runtime/semaphore.hpp"
+#include "runtime/stackWatermark.hpp"
#include "runtime/suspendedThreadTask.hpp"
#include "runtime/threadCrashProtection.hpp"
#include "runtime/threadSMR.hpp"
@@ -256,6 +257,11 @@
}
bool JfrThreadSampleClosure::sample_thread_in_java(JavaThread* thread, JfrStackFrame* frames, u4 max_frames) {
+ // Process the oops in the thread head before calling into code that wants to
+ // stack walk over Loom continuations. The stack walking code will otherwise
+ // skip frames in stack chunks on the Java heap.
+ StackWatermarkSet::start_processing(thread, StackWatermarkKind::gc);
+
OSThreadSampler sampler(thread, *this, frames, max_frames);
sampler.take_sample();
/* We don't want to allocate any memory using malloc/etc while the thread
@@ -274,6 +280,11 @@
}
bool JfrThreadSampleClosure::sample_thread_in_native(JavaThread* thread, JfrStackFrame* frames, u4 max_frames) {
+ // Process the oops in the thread head before calling into code that wants to
+ // stack walk over Loom continuations. The stack walking code will otherwise
+ // skip frames in stack chunks on the Java heap.
+ StackWatermarkSet::start_processing(thread, StackWatermarkKind::gc);
+
JfrNativeSamplerCallback cb(*this, thread, frames, max_frames);
if (JfrOptionSet::sample_protection()) {
ThreadCrashProtection crash_protection;
diff --git a/src/hotspot/share/jfr/recorder/stacktrace/jfrStackTrace.cpp b/src/hotspot/share/jfr/recorder/stacktrace/jfrStackTrace.cpp
index dd3b834..b82bde1 100644
--- a/src/hotspot/share/jfr/recorder/stacktrace/jfrStackTrace.cpp
+++ b/src/hotspot/share/jfr/recorder/stacktrace/jfrStackTrace.cpp
@@ -148,11 +148,23 @@
void next_vframe();
};
+static RegisterMap::WalkContinuation walk_continuation(JavaThread* jt) {
+ // NOTE: WalkContinuation::skip, because of interactions with ZGC relocation
+ // and load barriers. This code is run while generating stack traces for
+ // the ZPage allocation event, even when ZGC is relocating objects.
+ // When ZGC is relocating, it is forbidden to run code that performs
+ // load barriers. With WalkContinuation::include, we visit heap stack
+ // chunks and could be using load barriers.
+ return (UseZGC && !StackWatermarkSet::processing_started(jt))
+ ? RegisterMap::WalkContinuation::skip
+ : RegisterMap::WalkContinuation::include;
+}
+
JfrVframeStream::JfrVframeStream(JavaThread* jt, const frame& fr, bool stop_at_java_call_stub, bool async_mode) :
vframeStreamCommon(RegisterMap(jt,
RegisterMap::UpdateMap::skip,
RegisterMap::ProcessFrames::skip,
- RegisterMap::WalkContinuation::include)),
+ walk_continuation(jt))),
_cont_entry(JfrThreadLocal::is_vthread(jt) ? jt->last_continuation() : nullptr),
_async_mode(async_mode), _vthread(JfrThreadLocal::is_vthread(jt)) {
assert(!_vthread || _cont_entry != nullptr, "invariant");
