1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "signal_catcher.h"
18
19 #include <fcntl.h>
20 #include <pthread.h>
21 #include <signal.h>
22 #include <stdlib.h>
23 #include <sys/stat.h>
24 #include <sys/time.h>
25 #include <sys/types.h>
26 #include <unistd.h>
27
28 #include "base/unix_file/fd_file.h"
29 #include "class_linker.h"
30 #include "gc/heap.h"
31 #include "os.h"
32 #include "runtime.h"
33 #include "scoped_thread_state_change.h"
34 #include "signal_set.h"
35 #include "thread.h"
36 #include "thread_list.h"
37 #include "utils.h"
38
39 namespace art {
40
DumpCmdLine(std::ostream & os)41 static void DumpCmdLine(std::ostream& os) {
42 #if defined(__linux__)
43 // Show the original command line, and the current command line too if it's changed.
44 // On Android, /proc/self/cmdline will have been rewritten to something like "system_server".
45 std::string current_cmd_line;
46 if (ReadFileToString("/proc/self/cmdline", ¤t_cmd_line)) {
47 current_cmd_line.resize(current_cmd_line.size() - 1); // Lose the trailing '\0'.
48 std::replace(current_cmd_line.begin(), current_cmd_line.end(), '\0', ' ');
49
50 os << "Cmdline: " << current_cmd_line;
51 const char* stashed_cmd_line = GetCmdLine();
52 if (stashed_cmd_line != NULL && current_cmd_line != stashed_cmd_line) {
53 os << "Original command line: " << stashed_cmd_line;
54 }
55 }
56 os << "\n";
57 #else
58 os << "Cmdline: " << GetCmdLine() << "\n";
59 #endif
60 }
61
SignalCatcher(const std::string & stack_trace_file)62 SignalCatcher::SignalCatcher(const std::string& stack_trace_file)
63 : stack_trace_file_(stack_trace_file),
64 lock_("SignalCatcher lock"),
65 cond_("SignalCatcher::cond_", lock_),
66 thread_(NULL) {
67 SetHaltFlag(false);
68
69 // Create a raw pthread; its start routine will attach to the runtime.
70 CHECK_PTHREAD_CALL(pthread_create, (&pthread_, NULL, &Run, this), "signal catcher thread");
71
72 Thread* self = Thread::Current();
73 MutexLock mu(self, lock_);
74 while (thread_ == NULL) {
75 cond_.Wait(self);
76 }
77 }
78
~SignalCatcher()79 SignalCatcher::~SignalCatcher() {
80 // Since we know the thread is just sitting around waiting for signals
81 // to arrive, send it one.
82 SetHaltFlag(true);
83 CHECK_PTHREAD_CALL(pthread_kill, (pthread_, SIGQUIT), "signal catcher shutdown");
84 CHECK_PTHREAD_CALL(pthread_join, (pthread_, NULL), "signal catcher shutdown");
85 }
86
SetHaltFlag(bool new_value)87 void SignalCatcher::SetHaltFlag(bool new_value) {
88 MutexLock mu(Thread::Current(), lock_);
89 halt_ = new_value;
90 }
91
ShouldHalt()92 bool SignalCatcher::ShouldHalt() {
93 MutexLock mu(Thread::Current(), lock_);
94 return halt_;
95 }
96
Output(const std::string & s)97 void SignalCatcher::Output(const std::string& s) {
98 if (stack_trace_file_.empty()) {
99 LOG(INFO) << s;
100 return;
101 }
102
103 ScopedThreadStateChange tsc(Thread::Current(), kWaitingForSignalCatcherOutput);
104 int fd = open(stack_trace_file_.c_str(), O_APPEND | O_CREAT | O_WRONLY, 0666);
105 if (fd == -1) {
106 PLOG(ERROR) << "Unable to open stack trace file '" << stack_trace_file_ << "'";
107 return;
108 }
109 UniquePtr<File> file(new File(fd, stack_trace_file_));
110 if (!file->WriteFully(s.data(), s.size())) {
111 PLOG(ERROR) << "Failed to write stack traces to '" << stack_trace_file_ << "'";
112 } else {
113 LOG(INFO) << "Wrote stack traces to '" << stack_trace_file_ << "'";
114 }
115 }
116
HandleSigQuit()117 void SignalCatcher::HandleSigQuit() {
118 Runtime* runtime = Runtime::Current();
119 ThreadList* thread_list = runtime->GetThreadList();
120
121 // Grab exclusively the mutator lock, set state to Runnable without checking for a pending
122 // suspend request as we're going to suspend soon anyway. We set the state to Runnable to avoid
123 // giving away the mutator lock.
124 thread_list->SuspendAll();
125 Thread* self = Thread::Current();
126 Locks::mutator_lock_->AssertExclusiveHeld(self);
127 const char* old_cause = self->StartAssertNoThreadSuspension("Handling SIGQUIT");
128 ThreadState old_state = self->SetStateUnsafe(kRunnable);
129
130 std::ostringstream os;
131 os << "\n"
132 << "----- pid " << getpid() << " at " << GetIsoDate() << " -----\n";
133
134 DumpCmdLine(os);
135
136 os << "Build type: " << (kIsDebugBuild ? "debug" : "optimized") << "\n";
137
138 runtime->DumpForSigQuit(os);
139
140 if (false) {
141 std::string maps;
142 if (ReadFileToString("/proc/self/maps", &maps)) {
143 os << "/proc/self/maps:\n" << maps;
144 }
145 }
146 os << "----- end " << getpid() << " -----\n";
147 CHECK_EQ(self->SetStateUnsafe(old_state), kRunnable);
148 if (self->ReadFlag(kCheckpointRequest)) {
149 self->RunCheckpointFunction();
150 self->AtomicClearFlag(kCheckpointRequest);
151 }
152 self->EndAssertNoThreadSuspension(old_cause);
153 thread_list->ResumeAll();
154
155 Output(os.str());
156 }
157
HandleSigUsr1()158 void SignalCatcher::HandleSigUsr1() {
159 LOG(INFO) << "SIGUSR1 forcing GC (no HPROF)";
160 Runtime::Current()->GetHeap()->CollectGarbage(false);
161 }
162
WaitForSignal(Thread * self,SignalSet & signals)163 int SignalCatcher::WaitForSignal(Thread* self, SignalSet& signals) {
164 ScopedThreadStateChange tsc(self, kWaitingInMainSignalCatcherLoop);
165
166 // Signals for sigwait() must be blocked but not ignored. We
167 // block signals like SIGQUIT for all threads, so the condition
168 // is met. When the signal hits, we wake up, without any signal
169 // handlers being invoked.
170 int signal_number = signals.Wait();
171 if (!ShouldHalt()) {
172 // Let the user know we got the signal, just in case the system's too screwed for us to
173 // actually do what they want us to do...
174 LOG(INFO) << *self << ": reacting to signal " << signal_number;
175
176 // If anyone's holding locks (which might prevent us from getting back into state Runnable), say so...
177 Runtime::Current()->DumpLockHolders(LOG(INFO));
178 }
179
180 return signal_number;
181 }
182
Run(void * arg)183 void* SignalCatcher::Run(void* arg) {
184 SignalCatcher* signal_catcher = reinterpret_cast<SignalCatcher*>(arg);
185 CHECK(signal_catcher != NULL);
186
187 Runtime* runtime = Runtime::Current();
188 CHECK(runtime->AttachCurrentThread("Signal Catcher", true, runtime->GetSystemThreadGroup(),
189 !runtime->IsCompiler()));
190
191 Thread* self = Thread::Current();
192 DCHECK_NE(self->GetState(), kRunnable);
193 {
194 MutexLock mu(self, signal_catcher->lock_);
195 signal_catcher->thread_ = self;
196 signal_catcher->cond_.Broadcast(self);
197 }
198
199 // Set up mask with signals we want to handle.
200 SignalSet signals;
201 signals.Add(SIGQUIT);
202 signals.Add(SIGUSR1);
203
204 while (true) {
205 int signal_number = signal_catcher->WaitForSignal(self, signals);
206 if (signal_catcher->ShouldHalt()) {
207 runtime->DetachCurrentThread();
208 return NULL;
209 }
210
211 switch (signal_number) {
212 case SIGQUIT:
213 signal_catcher->HandleSigQuit();
214 break;
215 case SIGUSR1:
216 signal_catcher->HandleSigUsr1();
217 break;
218 default:
219 LOG(ERROR) << "Unexpected signal %d" << signal_number;
220 break;
221 }
222 }
223 }
224
225 } // namespace art
226