[Isolates] linux: fix sampling profiler.

src/platform-linux.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 792 matching lines @@
   // Glibc doesn't provide a wrapper for gettid(2).
   return syscall(SYS_gettid);
 }
 
 
 static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 #ifndef V8_HOST_ARCH_MIPS
   USE(info);
   if (signal != SIGPROF) return;
   Isolate* isolate = Isolate::UncheckedCurrent();
-  if (isolate == NULL || !isolate->IsInUse()) return;
+  if (isolate == NULL || !isolate->IsInitialized() || !isolate->IsInUse()) {
+    // We require a fully initialized and entered isolate.
+    return;
+  }
   Sampler* sampler = isolate->logger()->sampler();
   if (sampler == NULL || !sampler->IsActive()) return;
 
   TickSample sample_obj;
   TickSample* sample = CpuProfiler::TickSampleEvent(isolate);
   if (sample == NULL) sample = &sample_obj;
 
   // Extracting the sample from the context is extremely machine dependent.
   ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(context);
   mcontext_t& mcontext = ucontext->uc_mcontext;
@@ skipping 51 matching lines @@
   static void AddActiveSampler(Sampler* sampler) {
     ScopedLock lock(mutex_);
     SamplerRegistry::AddActiveSampler(sampler);
     if (instance_ == NULL) {
       // Install a signal handler.
       struct sigaction sa;
       sa.sa_sigaction = ProfilerSignalHandler;
       sigemptyset(&sa.sa_mask);
       sa.sa_flags = SA_RESTART | SA_SIGINFO;
       signal_handler_installed_ =
-          (sigaction(SIGPROF, &sa, &old_signal_handler_) != 0);
+          (sigaction(SIGPROF, &sa, &old_signal_handler_) == 0);
 
       // Start a thread that sends SIGPROF signal to VM threads.
       instance_ = new SignalSender(sampler->interval());
       instance_->Start();
     } else {
       ASSERT(instance_->interval_ == sampler->interval());
     }
   }
 
   static void RemoveActiveSampler(Sampler* sampler) {
@@ skipping 132 matching lines @@
 
 void Sampler::Stop() {
   ASSERT(IsActive());
   SignalSender::RemoveActiveSampler(this);
   SetActive(false);
 }
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal