1 /*
2 * Copyright (c) 2012, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "classfile/javaThreadStatus.hpp"
26 #include "code/codeCache.inline.hpp"
27 #include "code/debugInfoRec.hpp"
28 #include "code/nmethod.hpp"
29 #include "interpreter/interpreter.hpp"
30 #include "jfr/jfrEvents.hpp"
31 #include "jfr/periodic/sampling/jfrCPUTimeThreadSampler.hpp"
32 #include "jfr/periodic/sampling/jfrSampleMonitor.hpp"
33 #include "jfr/periodic/sampling/jfrSampleRequest.hpp"
34 #include "jfr/periodic/sampling/jfrThreadSampling.hpp"
35 #include "jfr/recorder/stacktrace/jfrStackTrace.hpp"
36 #include "jfr/utilities/jfrTypes.hpp"
37 #include "memory/resourceArea.hpp"
38 #include "oops/method.hpp"
39 #include "runtime/continuation.hpp"
40 #include "runtime/frame.inline.hpp"
41 #include "runtime/javaThread.inline.hpp"
42 #include "runtime/stackFrameStream.inline.hpp"
43
44 template <typename EventType>
45 static inline void send_sample_event(const JfrTicks& start_time, const JfrTicks& end_time, traceid sid, traceid tid) {
46 EventType event(UNTIMED);
47 event.set_starttime(start_time);
48 event.set_endtime(end_time);
49 event.set_sampledThread(tid);
50 event.set_state(static_cast<u8>(JavaThreadStatus::RUNNABLE));
51 event.set_stackTrace(sid);
52 event.commit();
53 }
54
55 static inline void send_safepoint_latency_event(const JfrSampleRequest& request, const JfrTicks& end_time, traceid sid, const JavaThread* jt) {
56 assert(jt != nullptr, "invariant");
57 assert(!jt->jfr_thread_local()->has_cached_stack_trace(), "invariant");
58 EventSafepointLatency event(UNTIMED);
59 event.set_starttime(request._sample_ticks);
60 event.set_endtime(end_time);
61 if (event.should_commit()) {
62 event.set_threadState(_thread_in_Java);
63 jt->jfr_thread_local()->set_cached_stack_trace_id(sid);
64 event.commit();
65 jt->jfr_thread_local()->clear_cached_stack_trace();
66 }
67 }
68
69 static inline bool is_interpreter(const JfrSampleRequest& request) {
70 return request._sample_bcp != nullptr;
71 }
72
73 static inline bool is_in_continuation(const frame& frame, JavaThread* jt) {
74 return JfrThreadLocal::is_vthread(jt) &&
75 (Continuation::is_frame_in_continuation(jt, frame) || Continuation::is_continuation_enterSpecial(frame));
76 }
77
78 // A sampled interpreter frame is handled differently from a sampled compiler frame.
79 //
80 // The JfrSampleRequest description partially describes a _potential_ interpreter Java frame.
81 // It's partial because the sampler thread only sets the fp and bcp fields.
82 //
83 // We want to ensure that what we discovered inside interpreter code _really_ is what we assume, a valid interpreter frame.
84 //
85 // Therefore, instead of letting the sampler thread read what it believes to be a Method*, we delay until we are at a safepoint to ensure the Method* is valid.
86 //
87 // If the JfrSampleRequest represents a valid interpreter frame, the Method* is retrieved and the sender frame is returned per the sender_frame.
88 //
89 // If it is not a valid interpreter frame, then the JfrSampleRequest is invalidated, and the current frame is returned per the sender frame.
90 //
91 static bool compute_sender_frame(JfrSampleRequest& request, frame& sender_frame, bool& in_continuation, JavaThread* jt) {
92 assert(is_interpreter(request), "invariant");
93 assert(jt != nullptr, "invariant");
94 assert(jt->has_last_Java_frame(), "invariant");
95
96 // For a request representing an interpreter frame, request._sample_sp is actually the frame pointer, fp.
97 const void* const sampled_fp = request._sample_sp;
98
99 StackFrameStream stream(jt, false, false);
100
101 // Search for the sampled interpreter frame and get its Method*.
102
103 while (!stream.is_done()) {
104 const frame* const frame = stream.current();
105 assert(frame != nullptr, "invariant");
106 const intptr_t* const real_fp = frame->real_fp();
107 assert(real_fp != nullptr, "invariant");
108 if (real_fp == sampled_fp && frame->is_interpreted_frame()) {
109 Method* const method = frame->interpreter_frame_method();
110 assert(method != nullptr, "invariant");
111 request._sample_pc = method;
112 // Got the Method*. Validate bcp.
113 if (!method->is_native() && !method->contains(static_cast<address>(request._sample_bcp))) {
114 request._sample_bcp = frame->interpreter_frame_bcp();
115 }
116 in_continuation = is_in_continuation(*frame, jt);
117 break;
118 }
119 if (real_fp >= sampled_fp) {
120 // What we sampled is not an official interpreter frame.
121 // Invalidate the sample request and use current.
122 request._sample_bcp = nullptr;
123 sender_frame = *stream.current();
124 in_continuation = is_in_continuation(sender_frame, jt);
125 return true;
126 }
127 stream.next();
128 }
129
130 assert(!stream.is_done(), "invariant");
131
132 // Step to sender.
133 stream.next();
134
135 // If the top frame is in a continuation, check that the sender frame is too.
136 if (in_continuation && !is_in_continuation(*stream.current(), jt)) {
137 // Leave sender frame empty.
138 return true;
139 }
140
141 sender_frame = *stream.current();
142
143 assert(request._sample_pc != nullptr, "invariant");
144 assert(request._sample_bcp != nullptr, "invariant");
145 assert(Method::is_valid_method(static_cast<const Method*>(request._sample_pc)), "invariant");
146 assert(static_cast<const Method*>(request._sample_pc)->is_native() ||
147 static_cast<const Method*>(request._sample_pc)->contains(static_cast<address>(request._sample_bcp)), "invariant");
148 return true;
149 }
150
151 static inline const PcDesc* get_pc_desc(nmethod* nm, void* pc) {
152 assert(nm != nullptr, "invariant");
153 assert(pc != nullptr, "invariant");
154 return nm->pc_desc_near(static_cast<address>(pc));
155 }
156
157 static inline bool is_valid(const PcDesc* pc_desc) {
158 return pc_desc != nullptr && pc_desc->scope_decode_offset() != DebugInformationRecorder::serialized_null;
159 }
160
161 static bool compute_top_frame(const JfrSampleRequest& request, frame& top_frame, bool& in_continuation, JavaThread* jt, bool& biased) {
162 assert(jt != nullptr, "invariant");
163
164 if (!jt->has_last_Java_frame()) {
165 return false;
166 }
167
168 if (is_interpreter(request)) {
169 return compute_sender_frame(const_cast<JfrSampleRequest&>(request), top_frame, in_continuation, jt);
170 }
171
172 void* const sampled_pc = request._sample_pc;
173 CodeBlob* sampled_cb;
174 if (sampled_pc == nullptr || (sampled_cb = CodeCache::find_blob(sampled_pc)) == nullptr) {
175 // A biased sample is requested or no code blob.
176 top_frame = jt->last_frame();
177 in_continuation = is_in_continuation(top_frame, jt);
178 biased = true;
179 return true;
180 }
181
182 // We will never describe a sample request that represents an unparsable stub or blob.
183 assert(sampled_cb->frame_complete_offset() != CodeOffsets::frame_never_safe, "invariant");
184
185 const void* const sampled_sp = request._sample_sp;
186 assert(sampled_sp != nullptr, "invariant");
187
188 nmethod* const sampled_nm = sampled_cb->as_nmethod_or_null();
189
190 StackFrameStream stream(jt, false /* update registers */, false /* process frames */);
191
192 if (stream.current()->is_safepoint_blob_frame()) {
193 if (sampled_nm != nullptr) {
194 // Move to the physical sender frame of the SafepointBlob stub frame using the frame size, not the logical iterator.
195 const int safepoint_blob_stub_frame_size = stream.current()->cb()->frame_size();
196 intptr_t* const sender_sp = stream.current()->unextended_sp() + safepoint_blob_stub_frame_size;
197 if (sender_sp > sampled_sp) {
198 const address saved_exception_pc = jt->saved_exception_pc();
199 assert(saved_exception_pc != nullptr, "invariant");
200 const nmethod* const exception_nm = CodeCache::find_blob(saved_exception_pc)->as_nmethod();
201 assert(exception_nm != nullptr, "invariant");
202 if (exception_nm == sampled_nm && sampled_nm->is_at_poll_return(saved_exception_pc)) {
203 // We sit at the poll return site in the sampled compiled nmethod with only the return address on the stack.
204 // The sampled_nm compiled frame is no longer extant, but we might be able to reconstruct a synthetic
205 // compiled frame at this location. We do this by overlaying a reconstructed frame on top of
206 // the huge SafepointBlob stub frame. Of course, the synthetic frame only contains random stack memory,
207 // but it is safe because stack walking cares only about the form of the frame (i.e., an sp and a pc).
208 // We also do not have to worry about stackbanging because we currently have a huge SafepointBlob stub frame
209 // on the stack. For extra assurance, we know that we can create this frame size at this
210 // very location because we just popped such a frame before we hit the return poll site.
211 //
212 // Let's attempt to correct for the safepoint bias.
213 const PcDesc* const pc_desc = get_pc_desc(sampled_nm, sampled_pc);
214 if (is_valid(pc_desc)) {
215 intptr_t* const synthetic_sp = sender_sp - sampled_nm->frame_size();
216 intptr_t* const synthetic_fp = sender_sp AARCH64_ONLY( - frame::sender_sp_offset);
217 top_frame = frame(synthetic_sp, synthetic_sp, synthetic_fp, pc_desc->real_pc(sampled_nm), sampled_nm);
218 in_continuation = is_in_continuation(top_frame, jt);
219 return true;
220 }
221 }
222 }
223 }
224 stream.next(); // skip the SafepointBlob stub frame
225 }
226
227 assert(!stream.current()->is_safepoint_blob_frame(), "invariant");
228
229 biased = true;
230
231 // Search the first frame that is above the sampled sp.
232 for (; !stream.is_done(); stream.next()) {
233 frame* const current = stream.current();
234
235 if (current->real_fp() <= sampled_sp) {
236 // Continue searching for a matching frame.
237 continue;
238 }
239
240 if (sampled_nm == nullptr) {
241 // The sample didn't have an nmethod; we decide to trace from its sender.
242 // Another instance of safepoint bias.
243 top_frame = *current;
244 break;
245 }
246
247 // Check for a matching compiled method.
248 if (current->cb()->as_nmethod_or_null() == sampled_nm) {
249 if (current->pc() != sampled_pc) {
250 // Let's adjust for the safepoint bias if we can.
251 const PcDesc* const pc_desc = get_pc_desc(sampled_nm, sampled_pc);
252 if (is_valid(pc_desc)) {
253 current->adjust_pc(pc_desc->real_pc(sampled_nm));
254 biased = false;
255 }
256 }
257 }
258 // Either a hit or a mismatched sample in which case we trace from the sender.
259 // Yet another instance of safepoint bias,to be addressed with
260 // more exact and stricter versions when parsable blobs become available.
261 top_frame = *current;
262 break;
263 }
264
265 in_continuation = is_in_continuation(top_frame, jt);
266 return true;
267 }
268
269 static void record_thread_in_java(const JfrSampleRequest& request, const JfrTicks& now, const JfrThreadLocal* tl, JavaThread* jt, Thread* current) {
270 assert(jt != nullptr, "invariant");
271 assert(tl != nullptr, "invariant");
272 assert(current != nullptr, "invariant");
273
274 frame top_frame;
275 bool biased = false;
276 bool in_continuation;
277 if (!compute_top_frame(request, top_frame, in_continuation, jt, biased)) {
278 return;
279 }
280
281 traceid sid;
282 {
283 ResourceMark rm(current);
284 JfrStackTrace stacktrace;
285 if (!stacktrace.record(jt, top_frame, in_continuation, request)) {
286 // Unable to record stacktrace. Fail.
287 return;
288 }
289 sid = JfrStackTraceRepository::add(stacktrace);
290 }
291 assert(sid != 0, "invariant");
292 const traceid tid = in_continuation ? tl->vthread_id_with_epoch_update(jt) : JfrThreadLocal::jvm_thread_id(jt);
293 send_sample_event<EventExecutionSample>(request._sample_ticks, now, sid, tid);
294 if (current == jt) {
295 send_safepoint_latency_event(request, now, sid, jt);
296 }
297 }
298
299 #ifdef LINUX
300 static void record_cpu_time_thread(const JfrCPUTimeSampleRequest& request, const JfrTicks& now, const JfrThreadLocal* tl, JavaThread* jt, Thread* current) {
301 assert(jt != nullptr, "invariant");
302 assert(tl != nullptr, "invariant");
303 assert(current != nullptr, "invariant");
304 frame top_frame;
305 bool biased = false;
306 bool in_continuation = false;
307 bool could_compute_top_frame = compute_top_frame(request._request, top_frame, in_continuation, jt, biased);
308 const traceid tid = in_continuation ? tl->vthread_id_with_epoch_update(jt) : JfrThreadLocal::jvm_thread_id(jt);
309
310 if (!could_compute_top_frame) {
311 JfrCPUTimeThreadSampling::send_empty_event(request._request._sample_ticks, tid, request._cpu_time_period);
312 return;
313 }
314 traceid sid;
315 {
316 ResourceMark rm(current);
317 JfrStackTrace stacktrace;
318 if (!stacktrace.record(jt, top_frame, in_continuation, request._request)) {
319 // Unable to record stacktrace. Fail.
320 JfrCPUTimeThreadSampling::send_empty_event(request._request._sample_ticks, tid, request._cpu_time_period);
321 return;
322 }
323 sid = JfrStackTraceRepository::add(stacktrace);
324 }
325 assert(sid != 0, "invariant");
326
327
328 JfrCPUTimeThreadSampling::send_event(request._request._sample_ticks, sid, tid, request._cpu_time_period, biased);
329 if (current == jt) {
330 send_safepoint_latency_event(request._request, now, sid, jt);
331 }
332 }
333 #endif
334
335 static void drain_enqueued_requests(const JfrTicks& now, JfrThreadLocal* tl, JavaThread* jt, Thread* current) {
336 assert(tl != nullptr, "invariant");
337 assert(jt != nullptr, "invariant");
338 assert(current != nullptr, "invariant");
339 assert(jt->jfr_thread_local() == tl, "invariant");
340 assert_lock_strong(tl->sample_monitor());
341 if (tl->has_enqueued_requests()) {
342 for (const JfrSampleRequest& request : *tl->sample_requests()) {
343 record_thread_in_java(request, now, tl, jt, current);
344 }
345 tl->clear_enqueued_requests();
346 }
347 assert(!tl->has_enqueued_requests(), "invariant");
348 }
349
350 static void drain_enqueued_cpu_time_requests(const JfrTicks& now, JfrThreadLocal* tl, JavaThread* jt, Thread* current, bool lock) {
351 assert(tl != nullptr, "invariant");
352 assert(jt != nullptr, "invariant");
353 assert(current != nullptr, "invariant");
354 #ifdef LINUX
355 tl->set_do_async_processing_of_cpu_time_jfr_requests(false);
356 if (lock) {
357 tl->acquire_cpu_time_jfr_dequeue_lock();
358 }
359 JfrCPUTimeTraceQueue& queue = tl->cpu_time_jfr_queue();
360 for (u4 i = 0; i < queue.size(); i++) {
361 record_cpu_time_thread(queue.at(i), now, tl, jt, current);
362 }
363 queue.clear();
364 assert(queue.is_empty(), "invariant");
365 tl->set_has_cpu_time_jfr_requests(false);
366 if (queue.lost_samples() > 0) {
367 JfrCPUTimeThreadSampling::send_lost_event( now, JfrThreadLocal::thread_id(jt), queue.get_and_reset_lost_samples());
368 queue.resize_if_needed();
369 }
370 if (lock) {
371 tl->release_cpu_time_jfr_queue_lock();
372 }
373 #endif
374 }
375
376 // Entry point for a thread that has been sampled in native code and has a pending JFR CPU time request.
377 void JfrThreadSampling::process_cpu_time_request(JavaThread* jt, JfrThreadLocal* tl, Thread* current, bool lock) {
378 assert(jt != nullptr, "invariant");
379
380 const JfrTicks now = JfrTicks::now();
381 drain_enqueued_cpu_time_requests(now, tl, jt, current, lock);
382 }
383
384 static void drain_all_enqueued_requests(const JfrTicks& now, JfrThreadLocal* tl, JavaThread* jt, Thread* current) {
385 assert(tl != nullptr, "invariant");
386 assert(jt != nullptr, "invariant");
387 assert(current != nullptr, "invariant");
388 drain_enqueued_requests(now, tl, jt, current);
389 if (tl->has_cpu_time_jfr_requests()) {
390 drain_enqueued_cpu_time_requests(now, tl, jt, current, true);
391 }
392 }
393
394 // Only entered by the JfrSampler thread.
395 bool JfrThreadSampling::process_native_sample_request(JfrThreadLocal* tl, JavaThread* jt, Thread* sampler_thread) {
396 assert(tl != nullptr, "invairant");
397 assert(jt != nullptr, "invariant");
398 assert(sampler_thread != nullptr, "invariant");
399 assert(sampler_thread->is_JfrSampler_thread(), "invariant");
400 assert(tl == jt->jfr_thread_local(), "invariant");
401 assert(jt != sampler_thread, "only asynchronous processing of native samples");
402 assert(jt->has_last_Java_frame(), "invariant");
403 assert(tl->sample_state() >= NATIVE_SAMPLE, "invariant");
404
405 assert_lock_strong(Threads_lock);
406
407 const JfrTicks start_time = JfrTicks::now();
408
409 traceid tid;
410 traceid sid;
411
412 {
413 JfrSampleMonitor sm(tl);
414
415 // Because the thread was in native, it is in a walkable state, because
416 // it will hit a safepoint poll on the way back from native. To ensure timely
417 // progress, any requests in the queue can be safely processed now.
418 drain_enqueued_requests(start_time, tl, jt, sampler_thread);
419 // Process the current stacktrace using the ljf.
420 {
421 ResourceMark rm(sampler_thread);
422 JfrStackTrace stacktrace;
423 const frame top_frame = jt->last_frame();
424 if (!stacktrace.record_inner(jt, top_frame, is_in_continuation(top_frame, jt), 0 /* skip level */)) {
425 // Unable to record stacktrace. Fail.
426 return false;
427 }
428 sid = JfrStackTraceRepository::add(stacktrace);
429 }
430 // Read the tid under the monitor to ensure that if its a virtual thread,
431 // it is not unmounted until we are done with it.
432 tid = JfrThreadLocal::thread_id(jt);
433 }
434
435 assert(tl->sample_state() == NO_SAMPLE, "invariant");
436 send_sample_event<EventNativeMethodSample>(start_time, start_time, sid, tid);
437 return true;
438 }
439
440 // Entry point for a sampled thread that discovered pending Jfr Sample Requests as part of a safepoint poll.
441 void JfrThreadSampling::process_sample_request(JavaThread* jt) {
442 assert(JavaThread::current() == jt, "should be current thread");
443 assert(jt->thread_state() == _thread_in_vm || jt->thread_state() == _thread_in_Java, "invariant");
444
445 const JfrTicks now = JfrTicks::now();
446
447 JfrThreadLocal* const tl = jt->jfr_thread_local();
448 assert(tl != nullptr, "invariant");
449
450 MonitorLocker ml(tl->sample_monitor(), Monitor::_no_safepoint_check_flag);
451
452 for (;;) {
453 const int sample_state = tl->sample_state();
454 if (sample_state == NATIVE_SAMPLE) {
455 tl->set_sample_state(WAITING_FOR_NATIVE_SAMPLE);
456 // Wait until stack trace is processed.
457 ml.wait();
458 } else if (sample_state == JAVA_SAMPLE) {
459 tl->enqueue_request();
460 } else if (sample_state == WAITING_FOR_NATIVE_SAMPLE) {
461 // Handle spurious wakeups. Again wait until stack trace is processed.
462 ml.wait();
463 } else {
464 // State has been processed.
465 break;
466 }
467 }
468 drain_all_enqueued_requests(now, tl, jt, jt);
469 }
470