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      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 
     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", &current_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 
     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 
     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 
     87 void SignalCatcher::SetHaltFlag(bool new_value) {
     88   MutexLock mu(Thread::Current(), lock_);
     89   halt_ = new_value;
     90 }
     91 
     92 bool SignalCatcher::ShouldHalt() {
     93   MutexLock mu(Thread::Current(), lock_);
     94   return halt_;
     95 }
     96 
     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 
    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 
    158 void SignalCatcher::HandleSigUsr1() {
    159   LOG(INFO) << "SIGUSR1 forcing GC (no HPROF)";
    160   Runtime::Current()->GetHeap()->CollectGarbage(false);
    161 }
    162 
    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 
    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