1 /* Copyright (C) 2017 The Android Open Source Project
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4  * This file implements interfaces from the file jvmti.h. This implementation
5  * is licensed under the same terms as the file jvmti.h.  The
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9  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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31 
32 #ifndef ART_OPENJDKJVMTI_TI_THREAD_H_
33 #define ART_OPENJDKJVMTI_TI_THREAD_H_
34 
35 #include <unordered_map>
36 
37 #include "jni.h"
38 #include "jvmti.h"
39 
40 #include "base/macros.h"
41 #include "base/mutex.h"
42 #include "thread.h"
43 
44 namespace art {
45 class ArtField;
46 class ScopedObjectAccessAlreadyRunnable;
47 class Thread;
48 class Closure;
49 }  // namespace art
50 
51 namespace openjdkjvmti {
52 
53 class EventHandler;
54 
55 // Gains the user_code_suspension_lock_ and ensures that the code will not suspend for user-code.
56 class SCOPED_CAPABILITY ScopedNoUserCodeSuspension {
57  public:
58   explicit ScopedNoUserCodeSuspension(art::Thread* self)
59       ACQUIRE(art::Locks::user_code_suspension_lock_);
60   ~ScopedNoUserCodeSuspension() RELEASE(art::Locks::user_code_suspension_lock_);
61 
62  private:
63   art::Thread* self_;
64 };
65 
66 // The struct that we store in the art::Thread::custom_tls_ that maps the jvmtiEnvs to the data
67 // stored with that thread. This is needed since different jvmtiEnvs are not supposed to share TLS
68 // data but we only have a single slot in Thread objects to store data.
69 struct JvmtiGlobalTLSData : public art::TLSData {
70   std::unordered_map<jvmtiEnv*, const void*> data GUARDED_BY(art::Locks::thread_list_lock_);
71 
72   // The depth of the last frame where popping using PopFrame it is not allowed. It is set to
73   // kNoDisallowedPopFrame if all frames can be popped. See b/117615146 for more information.
74   static constexpr size_t kNoDisallowedPopFrame = -1;
75   size_t disable_pop_frame_depth = kNoDisallowedPopFrame;
76 };
77 
78 class ThreadUtil {
79  public:
80   static void Register(EventHandler* event_handler);
81   static void Unregister();
82 
83   // To be called when it is safe to cache data. This means that we have at least entered the
84   // RuntimePhase::kInit but we might or might not have already called VMInit event.
85   static void CacheData();
86 
87   // Called just after we have sent the VMInit callback so that ThreadUtil can do final setup. This
88   // ensures that there are no timing issues between the two callbacks.
89   static void VMInitEventSent() REQUIRES_SHARED(art::Locks::mutator_lock_);
90 
91   // Handle a jvmtiEnv going away.
92   static void RemoveEnvironment(jvmtiEnv* env);
93 
94   static jvmtiError GetAllThreads(jvmtiEnv* env, jint* threads_count_ptr, jthread** threads_ptr);
95 
96   static jvmtiError GetCurrentThread(jvmtiEnv* env, jthread* thread_ptr);
97 
98   static jvmtiError GetThreadInfo(jvmtiEnv* env, jthread thread, jvmtiThreadInfo* info_ptr);
99 
100   static jvmtiError GetThreadState(jvmtiEnv* env, jthread thread, jint* thread_state_ptr);
101 
102   static jvmtiError SetThreadLocalStorage(jvmtiEnv* env, jthread thread, const void* data);
103   static jvmtiError GetThreadLocalStorage(jvmtiEnv* env, jthread thread, void** data_ptr);
104 
105   static jvmtiError RunAgentThread(jvmtiEnv* env,
106                                    jthread thread,
107                                    jvmtiStartFunction proc,
108                                    const void* arg,
109                                    jint priority);
110 
111   static jvmtiError SuspendThread(jvmtiEnv* env, jthread thread);
112   static jvmtiError ResumeThread(jvmtiEnv* env, jthread thread);
113 
114   static jvmtiError SuspendThreadList(jvmtiEnv* env,
115                                       jint request_count,
116                                       const jthread* threads,
117                                       jvmtiError* results);
118   static jvmtiError ResumeThreadList(jvmtiEnv* env,
119                                      jint request_count,
120                                      const jthread* threads,
121                                      jvmtiError* results);
122 
123   static jvmtiError StopThread(jvmtiEnv* env, jthread thr, jobject exception);
124   static jvmtiError InterruptThread(jvmtiEnv* env, jthread thr);
125 
126   // Returns true if we decoded the thread and it is alive, false otherwise with an appropriate
127   // error placed into 'err'. A thread is alive if it has had it's 'start' function called and has
128   // (or at least could have) executed managed code and has not yet returned past it's first managed
129   // frame. This means that the thread returned might have IsStillStarting() return true. Code that
130   // does not consider that alive should check manually.
131   static bool GetAliveNativeThread(jthread thread,
132                                    const art::ScopedObjectAccessAlreadyRunnable& soa,
133                                    /*out*/ art::Thread** thr,
134                                    /*out*/ jvmtiError* err)
135       REQUIRES_SHARED(art::Locks::mutator_lock_)
136       REQUIRES(art::Locks::thread_list_lock_);
137 
138   // Returns true if we decoded the thread, false otherwise with an appropriate error placed into
139   // 'err'
140   static bool GetNativeThread(jthread thread,
141                               const art::ScopedObjectAccessAlreadyRunnable& soa,
142                               /*out*/ art::Thread** thr,
143                               /*out*/ jvmtiError* err)
144       REQUIRES_SHARED(art::Locks::mutator_lock_)
145       REQUIRES(art::Locks::thread_list_lock_);
146 
147   // Go to sleep if this thread is suspended.
148   static void SuspendCheck(art::Thread* self)
149     REQUIRES(!art::Locks::mutator_lock_, !art::Locks::user_code_suspension_lock_);
150 
151   // Returns true if the thread would be suspended if it locks the mutator-lock or calls
152   // SuspendCheck. This function is called with the user_code_suspension_lock already held.
153   static bool WouldSuspendForUserCodeLocked(art::Thread* self)
154     REQUIRES(art::Locks::user_code_suspension_lock_,
155              !art::Locks::thread_suspend_count_lock_);
156 
157   // Returns true if this thread would go to sleep if it locks the mutator-lock or calls
158   // SuspendCheck.
159   static bool WouldSuspendForUserCode(art::Thread* self)
160     REQUIRES(!art::Locks::user_code_suspension_lock_,
161              !art::Locks::thread_suspend_count_lock_);
162 
163   static JvmtiGlobalTLSData* GetGlobalTLSData(art::Thread* thread)
164       REQUIRES(art::Locks::thread_list_lock_);
165   static JvmtiGlobalTLSData* GetOrCreateGlobalTLSData(art::Thread* thread)
166       REQUIRES(art::Locks::thread_list_lock_);
167 
168  private:
169   // We need to make sure only one thread tries to suspend threads at a time so we can get the
170   // 'suspend-only-once' behavior the spec requires. Internally, ART considers suspension to be a
171   // counted state, allowing a single thread to be suspended multiple times by different users. This
172   // makes mapping into the JVMTI idea of thread suspension difficult. We have decided to split the
173   // difference and ensure that JVMTI tries to treat suspension as the boolean flag as much as
174   // possible with the suspend/resume methods but only do best effort. On the other hand
175   // GetThreadState will be totally accurate as much as possible. This means that calling
176   // ResumeThread on a thread that has state JVMTI_THREAD_STATE_SUSPENDED will not necessarily
177   // cause the thread to wake up if the thread is suspended for the debugger or gc or something.
178   static jvmtiError SuspendSelf(art::Thread* self)
179       REQUIRES(!art::Locks::mutator_lock_, !art::Locks::user_code_suspension_lock_);
180   static jvmtiError SuspendOther(art::Thread* self, jthread target_jthread)
181       REQUIRES(!art::Locks::mutator_lock_, !art::Locks::user_code_suspension_lock_);
182 
183   static art::ArtField* context_class_loader_;
184 };
185 
186 }  // namespace openjdkjvmti
187 
188 #endif  // ART_OPENJDKJVMTI_TI_THREAD_H_
189