1// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
2// for details. All rights reserved. Use of this source code is governed by a
3// BSD-style license that can be found in the LICENSE file.
4
5#ifndef RUNTIME_VM_THREAD_INTERRUPTER_H_
6#define RUNTIME_VM_THREAD_INTERRUPTER_H_
7
8#include "vm/allocation.h"
9#include "vm/os_thread.h"
10#include "vm/signal_handler.h"
11#include "vm/thread.h"
12
13namespace dart {
14
15struct InterruptedThreadState {
16 uintptr_t pc;
17 uintptr_t csp;
18 uintptr_t dsp;
19 uintptr_t fp;
20 uintptr_t lr;
21};
22
23class ThreadInterrupter : public AllStatic {
24 public:
25 static void Init();
26
27 static void Startup();
28 static void Cleanup();
29
30 // Delay between interrupts.
31 static void SetInterruptPeriod(intptr_t period);
32
33 // Wake up the thread interrupter thread.
34 static void WakeUp();
35
36 // Interrupt a thread.
37 static void InterruptThread(OSThread* thread);
38
39 class SampleBufferWriterScope : public ValueObject {
40 public:
41 SampleBufferWriterScope() {
42 intptr_t old_value = sample_buffer_lock_.load(std::memory_order_relaxed);
43 intptr_t new_value;
44 do {
45 if (old_value < 0) {
46 entered_lock_ = false;
47 return;
48 }
49 new_value = old_value + 1;
50 } while (!sample_buffer_lock_.compare_exchange_weak(
51 old_value, new_value, std::memory_order_acquire));
52 entered_lock_ = true;
53 }
54
55 ~SampleBufferWriterScope() {
56 if (!entered_lock_) return;
57 intptr_t old_value = sample_buffer_lock_.load(std::memory_order_relaxed);
58 intptr_t new_value;
59 do {
60 ASSERT(old_value > 0);
61 new_value = old_value - 1;
62 } while (!sample_buffer_lock_.compare_exchange_weak(
63 old_value, new_value, std::memory_order_release));
64 }
65
66 bool CanSample() const {
67 return entered_lock_ &&
68 sample_buffer_waiters_.load(std::memory_order_relaxed) == 0;
69 }
70
71 private:
72 bool entered_lock_;
73 DISALLOW_COPY_AND_ASSIGN(SampleBufferWriterScope);
74 };
75
76 class SampleBufferReaderScope : public ValueObject {
77 public:
78 SampleBufferReaderScope() { EnterSampleReader(); }
79 ~SampleBufferReaderScope() { ExitSampleReader(); }
80
81 private:
82 DISALLOW_COPY_AND_ASSIGN(SampleBufferReaderScope);
83 };
84
85 private:
86 static const intptr_t kMaxThreads = 4096;
87 static bool initialized_;
88 static bool shutdown_;
89 static bool thread_running_;
90 static bool woken_up_;
91 static ThreadJoinId interrupter_thread_id_;
92 static Monitor* monitor_;
93 static intptr_t interrupt_period_;
94 static intptr_t current_wait_time_;
95
96 // Something like a reader-writer lock. Positive values indictate there are
97 // outstanding signal handlers that can write to the sample buffer. Negative
98 // values indicate there are outstanding sample buffer processors that can
99 // read from the sample buffer. A reader will spin-wait to enter the lock. A
100 // writer will give up if it fails to enter lock, causing samples to be
101 // skipping while we are processing the sample buffer or trying to shut down.
102 static std::atomic<intptr_t> sample_buffer_lock_;
103 static std::atomic<intptr_t> sample_buffer_waiters_;
104
105 static bool IsDebuggerAttached();
106
107 static bool InDeepSleep() {
108 return current_wait_time_ == Monitor::kNoTimeout;
109 }
110
111 static void ThreadMain(uword parameters);
112
113 static void InstallSignalHandler();
114
115 static void RemoveSignalHandler();
116
117 static void EnterSampleReader() {
118 sample_buffer_waiters_.fetch_add(1, std::memory_order_relaxed);
119
120 intptr_t old_value = sample_buffer_lock_.load(std::memory_order_relaxed);
121 intptr_t new_value;
122 do {
123 if (old_value > 0) {
124 old_value = sample_buffer_lock_.load(std::memory_order_relaxed);
125 continue; // Spin waiting for outstanding SIGPROFs to complete.
126 }
127 new_value = old_value - 1;
128 } while (!sample_buffer_lock_.compare_exchange_weak(
129 old_value, new_value, std::memory_order_acquire));
130 }
131
132 static void ExitSampleReader() {
133 sample_buffer_waiters_.fetch_sub(1, std::memory_order_relaxed);
134
135 intptr_t old_value = sample_buffer_lock_.load(std::memory_order_relaxed);
136 intptr_t new_value;
137 do {
138 ASSERT(old_value < 0);
139 new_value = old_value + 1;
140 } while (!sample_buffer_lock_.compare_exchange_weak(
141 old_value, new_value, std::memory_order_release));
142 }
143
144 friend class ThreadInterrupterVisitIsolates;
145};
146
147} // namespace dart
148
149#endif // RUNTIME_VM_THREAD_INTERRUPTER_H_
150