diff --git a/src/monitor.cc b/src/monitor.cc
index aede4b8..b6f91bc 100644
--- a/src/monitor.cc
+++ b/src/monitor.cc
@@ -93,14 +93,25 @@
 #define LW_LOCK_COUNT_SHIFT 19
 #define LW_LOCK_COUNT(x) (((x) >> LW_LOCK_COUNT_SHIFT) & LW_LOCK_COUNT_MASK)
 
+bool (*Monitor::is_sensitive_thread_hook_)() = NULL;
 bool Monitor::is_verbose_ = false;
+uint32_t Monitor::lock_profiling_threshold_ = 0;
 
 bool Monitor::IsVerbose() {
   return is_verbose_;
 }
 
-void Monitor::SetVerbose(bool is_verbose) {
+bool Monitor::IsSensitiveThread() {
+  if (is_sensitive_thread_hook_ != NULL) {
+    return (*is_sensitive_thread_hook_)();
+  }
+  return false;
+}
+
+void Monitor::Init(bool is_verbose, uint32_t lock_profiling_threshold, bool (*is_sensitive_thread_hook)()) {
   is_verbose_ = is_verbose;
+  lock_profiling_threshold_ = lock_profiling_threshold;
+  is_sensitive_thread_hook_ = is_sensitive_thread_hook;
 }
 
 Monitor::Monitor(Object* obj)
@@ -182,158 +193,52 @@
   return obj_;
 }
 
-/*
-static char *logWriteInt(char *dst, int value) {
-  *dst++ = EVENT_TYPE_INT;
-  set4LE((uint8_t *)dst, value);
-  return dst + 4;
-}
-
-static char *logWriteString(char *dst, const char *value, size_t len) {
-  *dst++ = EVENT_TYPE_STRING;
-  len = len < 32 ? len : 32;
-  set4LE((uint8_t *)dst, len);
-  dst += 4;
-  memcpy(dst, value, len);
-  return dst + len;
-}
-
-#define EVENT_LOG_TAG_dvm_lock_sample 20003
-
-static void logContentionEvent(Thread *self, uint32_t waitMs, uint32_t samplePercent,
-                               const char *ownerFileName, uint32_t ownerLineNumber)
-{
-    const StackSaveArea *saveArea;
-    const Method *meth;
-    uint32_t relativePc;
-    char eventBuffer[174];
-    const char *fileName;
-    char procName[33];
-    char *cp;
-    size_t len;
-    int fd;
-
-    saveArea = SAVEAREA_FROM_FP(self->interpSave.curFrame);
-    meth = saveArea->method;
-    cp = eventBuffer;
-
-    // Emit the event list length, 1 byte.
-    *cp++ = 9;
-
-    // Emit the process name, <= 37 bytes.
-    fd = open("/proc/self/cmdline", O_RDONLY);
-    memset(procName, 0, sizeof(procName));
-    read(fd, procName, sizeof(procName) - 1);
-    close(fd);
-    len = strlen(procName);
-    cp = logWriteString(cp, procName, len);
-
-    // Emit the sensitive thread ("main thread") status, 5 bytes.
-    bool isSensitive = false;
-    if (gDvm.isSensitiveThreadHook != NULL) {
-        isSensitive = gDvm.isSensitiveThreadHook();
-    }
-    cp = logWriteInt(cp, isSensitive);
-
-    // Emit self thread name string, <= 37 bytes.
-    std::string selfName = dvmGetThreadName(self);
-    cp = logWriteString(cp, selfName.c_str(), selfName.size());
-
-    // Emit the wait time, 5 bytes.
-    cp = logWriteInt(cp, waitMs);
-
-    // Emit the source code file name, <= 37 bytes.
-    fileName = dvmGetMethodSourceFile(meth);
-    if (fileName == NULL) fileName = "";
-    cp = logWriteString(cp, fileName, strlen(fileName));
-
-    // Emit the source code line number, 5 bytes.
-    relativePc = saveArea->xtra.currentPc - saveArea->method->insns;
-    cp = logWriteInt(cp, dvmLineNumFromPC(meth, relativePc));
-
-    // Emit the lock owner source code file name, <= 37 bytes.
-    if (ownerFileName == NULL) {
-        ownerFileName = "";
-    } else if (strcmp(fileName, ownerFileName) == 0) {
-        // Common case, so save on log space.
-        ownerFileName = "-";
-    }
-    cp = logWriteString(cp, ownerFileName, strlen(ownerFileName));
-
-    // Emit the source code line number, 5 bytes.
-    cp = logWriteInt(cp, ownerLineNumber);
-
-    // Emit the sample percentage, 5 bytes.
-    cp = logWriteInt(cp, samplePercent);
-
-    assert((size_t)(cp - eventBuffer) <= sizeof(eventBuffer));
-    android_btWriteLog(EVENT_LOG_TAG_dvm_lock_sample,
-                       EVENT_TYPE_LIST,
-                       eventBuffer,
-                       (size_t)(cp - eventBuffer));
-}
-*/
-
 void Monitor::Lock(Thread* self) {
-//  uint32_t waitThreshold, samplePercent;
-//  uint64_t waitStart, waitEnd, waitMs;
-
   if (owner_ == self) {
     lock_count_++;
     return;
   }
+
+  uint64_t waitStart, waitEnd;
   if (!lock_.TryLock()) {
+    uint32_t wait_threshold = lock_profiling_threshold_;
+    const char* current_owner_filename = NULL;
+    uint32_t current_owner_line_number = -1;
     {
       ScopedThreadStateChange tsc(self, Thread::kBlocked);
-//      waitThreshold = gDvm.lockProfThreshold;
-//      if (waitThreshold) {
-//        waitStart = dvmGetRelativeTimeUsec();
-//      }
-//      const char* currentOwnerFileName = mon->ownerFileName;
-//      uint32_t currentOwnerLineNumber = mon->ownerLineNumber;
+      if (wait_threshold != 0) {
+        waitStart = NanoTime() / 1000;
+      }
+      current_owner_filename = owner_filename_;
+      current_owner_line_number = owner_line_number_;
 
       lock_.Lock();
-//      if (waitThreshold) {
-//        waitEnd = dvmGetRelativeTimeUsec();
-//      }
+      if (wait_threshold != 0) {
+        waitEnd = NanoTime() / 1000;
+      }
     }
-//    if (waitThreshold) {
-//      waitMs = (waitEnd - waitStart) / 1000;
-//      if (waitMs >= waitThreshold) {
-//        samplePercent = 100;
-//      } else {
-//        samplePercent = 100 * waitMs / waitThreshold;
-//      }
-//      if (samplePercent != 0 && ((uint32_t)rand() % 100 < samplePercent)) {
-//        logContentionEvent(self, waitMs, samplePercent, currentOwnerFileName, currentOwnerLineNumber);
-//      }
-//    }
+
+    if (wait_threshold != 0) {
+      uint64_t wait_ms = (waitEnd - waitStart) / 1000;
+      uint32_t sample_percent;
+      if (wait_ms >= wait_threshold) {
+        sample_percent = 100;
+      } else {
+        sample_percent = 100 * wait_ms / wait_threshold;
+      }
+      if (sample_percent != 0 && (static_cast<uint32_t>(rand() % 100) < sample_percent)) {
+        LogContentionEvent(self, wait_ms, sample_percent, current_owner_filename, current_owner_line_number);
+      }
+    }
   }
   owner_ = self;
   DCHECK_EQ(lock_count_, 0);
 
   // When debugging, save the current monitor holder for future
   // acquisition failures to use in sampled logging.
-//  if (gDvm.lockProfThreshold > 0) {
-//    const StackSaveArea *saveArea;
-//    const Method *meth;
-//    mon->ownerLineNumber = 0;
-//    if (self->interpSave.curFrame == NULL) {
-//      mon->ownerFileName = "no_frame";
-//    } else if ((saveArea = SAVEAREA_FROM_FP(self->interpSave.curFrame)) == NULL) {
-//      mon->ownerFileName = "no_save_area";
-//    } else if ((meth = saveArea->method) == NULL) {
-//      mon->ownerFileName = "no_method";
-//    } else {
-//      uint32_t relativePc = saveArea->xtra.currentPc - saveArea->method->insns;
-//      mon->ownerFileName = (char*) dvmGetMethodSourceFile(meth);
-//      if (mon->ownerFileName == NULL) {
-//        mon->ownerFileName = "no_method_file";
-//      } else {
-//        mon->ownerLineNumber = dvmLineNumFromPC(meth, relativePc);
-//      }
-//    }
-//  }
+  if (lock_profiling_threshold_ != 0) {
+    self->GetCurrentLocation(owner_filename_, owner_line_number_);
+  }
 }
 
 void ThrowIllegalMonitorStateException(const char* msg) {
diff --git a/src/monitor.h b/src/monitor.h
index 829f0fb..632c5d3 100644
--- a/src/monitor.h
+++ b/src/monitor.h
@@ -63,7 +63,8 @@
   ~Monitor();
 
   static bool IsVerbose();
-  static void SetVerbose(bool is_verbose);
+  static bool IsSensitiveThread();
+  static void Init(bool is_verbose, uint32_t lock_profiling_threshold, bool (*is_sensitive_thread_hook)());
 
   static uint32_t GetThinLockId(uint32_t raw_lock_word);
 
@@ -86,6 +87,8 @@
 
   static void Inflate(Thread* self, Object* obj);
 
+  void LogContentionEvent(Thread* self, uint32_t wait_ms, uint32_t sample_percent, const char* owner_filename, uint32_t owner_line_number);
+
   void Lock(Thread* self);
   bool Unlock(Thread* thread);
 
@@ -94,7 +97,9 @@
 
   void Wait(Thread* self, int64_t msec, int32_t nsec, bool interruptShouldThrow);
 
+  static bool (*is_sensitive_thread_hook_)();
   static bool is_verbose_;
+  static uint32_t lock_profiling_threshold_;
 
   /* Which thread currently owns the lock? */
   Thread* owner_;
diff --git a/src/monitor_android.cc b/src/monitor_android.cc
new file mode 100644
index 0000000..95dd397
--- /dev/null
+++ b/src/monitor_android.cc
@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "monitor.h"
+#include "object.h"
+#include "thread.h"
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "cutils/log.h"
+
+#define EVENT_LOG_TAG_dvm_lock_sample 20003
+
+namespace art {
+
+static void Set4LE(uint8_t* buf, uint32_t val) {
+  *buf++ = (uint8_t)(val);
+  *buf++ = (uint8_t)(val >> 8);
+  *buf++ = (uint8_t)(val >> 16);
+  *buf = (uint8_t)(val >> 24);
+}
+
+static char* EventLogWriteInt(char* dst, int value) {
+  *dst++ = EVENT_TYPE_INT;
+  Set4LE((uint8_t*) dst, value);
+  return dst + 4;
+}
+
+static char* EventLogWriteString(char* dst, const char* value, size_t len) {
+  *dst++ = EVENT_TYPE_STRING;
+  len = len < 32 ? len : 32;
+  Set4LE((uint8_t*) dst, len);
+  dst += 4;
+  memcpy(dst, value, len);
+  return dst + len;
+}
+
+void Monitor::LogContentionEvent(Thread* self, uint32_t wait_ms, uint32_t sample_percent, const char* owner_filename, uint32_t owner_line_number) {
+  // Emit the event list length, 1 byte.
+  char eventBuffer[174];
+  char* cp = eventBuffer;
+  *cp++ = 9;
+
+  // Emit the process name, <= 37 bytes.
+  int fd = open("/proc/self/cmdline", O_RDONLY);
+  char procName[33];
+  memset(procName, 0, sizeof(procName));
+  read(fd, procName, sizeof(procName) - 1);
+  close(fd);
+  size_t len = strlen(procName);
+  cp = EventLogWriteString(cp, procName, len);
+
+  // Emit the sensitive thread ("main thread") status, 5 bytes.
+  cp = EventLogWriteInt(cp, Monitor::IsSensitiveThread());
+
+  // Emit self thread name string, <= 37 bytes.
+  std::string thread_name(self->GetName()->ToModifiedUtf8());
+  cp = EventLogWriteString(cp, thread_name.c_str(), thread_name.size());
+
+  // Emit the wait time, 5 bytes.
+  cp = EventLogWriteInt(cp, wait_ms);
+
+  // Emit the source code file name, <= 37 bytes.
+  const char* filename;
+  uint32_t line_number;
+  self->GetCurrentLocation(filename, line_number);
+  cp = EventLogWriteString(cp, filename, strlen(filename));
+
+  // Emit the source code line number, 5 bytes.
+  cp = EventLogWriteInt(cp, line_number);
+
+  // Emit the lock owner source code file name, <= 37 bytes.
+  if (owner_filename == NULL) {
+    owner_filename = "";
+  } else if (strcmp(filename, owner_filename) == 0) {
+    // Common case, so save on log space.
+    owner_filename = "-";
+  }
+  cp = EventLogWriteString(cp, owner_filename, strlen(owner_filename));
+
+  // Emit the source code line number, 5 bytes.
+  cp = EventLogWriteInt(cp, owner_line_number);
+
+  // Emit the sample percentage, 5 bytes.
+  cp = EventLogWriteInt(cp, sample_percent);
+
+  CHECK_LE((size_t)(cp - eventBuffer), sizeof(eventBuffer));
+  android_btWriteLog(EVENT_LOG_TAG_dvm_lock_sample, EVENT_TYPE_LIST, eventBuffer, (size_t)(cp - eventBuffer));
+}
+
+}  // namespace art
diff --git a/src/monitor_linux.cc b/src/monitor_linux.cc
new file mode 100644
index 0000000..856ebe4
--- /dev/null
+++ b/src/monitor_linux.cc
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "monitor.h"
+
+namespace art {
+
+void Monitor::LogContentionEvent(Thread*, uint32_t, uint32_t, const char*, uint32_t) {
+}
+
+}  // namespace art
diff --git a/src/runtime.cc b/src/runtime.cc
index fd9cc8c..31ba262 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -212,6 +212,9 @@
 
   parsed->is_zygote_ = false;
 
+  parsed->lock_profiling_threshold_ = 0;
+  parsed->hook_is_sensitive_thread_ = NULL;
+
   parsed->hook_vfprintf_ = vfprintf;
   parsed->hook_exit_ = exit;
   parsed->hook_abort_ = abort;
@@ -284,6 +287,10 @@
       for (size_t i = 0; i < verbose_options.size(); ++i) {
         parsed->verbose_.insert(verbose_options[i]);
       }
+    } else if (option.starts_with("-Xlockprofthreshold:")) {
+      parsed->lock_profiling_threshold_ = atoi(option.substr(strlen("-Xlockprofthreshold:")).data());
+    } else if (option == "sensitiveThread") {
+      parsed->hook_is_sensitive_thread_ = reinterpret_cast<bool (*)()>(options[i].second);
     } else if (option == "vfprintf") {
       parsed->hook_vfprintf_ = reinterpret_cast<int (*)(FILE *, const char*, va_list)>(options[i].second);
     } else if (option == "exit") {
@@ -430,7 +437,7 @@
     LOG(INFO) << "Runtime::Init -verbose:startup enabled";
   }
 
-  Monitor::SetVerbose(options->IsVerbose("monitor"));
+  Monitor::Init(options->IsVerbose("monitor"), options->lock_profiling_threshold_, options->hook_is_sensitive_thread_);
 
   host_prefix_ = options->host_prefix_;
   boot_class_path_ = options->boot_class_path_;
diff --git a/src/runtime.h b/src/runtime.h
index 1ca9dca..cbd47b8 100644
--- a/src/runtime.h
+++ b/src/runtime.h
@@ -56,6 +56,8 @@
     size_t heap_initial_size_;
     size_t heap_maximum_size_;
     size_t stack_size_;
+    uint32_t lock_profiling_threshold_;
+    bool (*hook_is_sensitive_thread_)();
     jint (*hook_vfprintf_)(FILE* stream, const char* format, va_list ap);
     void (*hook_exit_)(jint status);
     void (*hook_abort_)();
diff --git a/src/thread.cc b/src/thread.cc
index 95c2995..e72046c 100644
--- a/src/thread.cc
+++ b/src/thread.cc
@@ -364,6 +364,10 @@
   return "";
 }
 
+String* Thread::GetName() const {
+  return (peer_ != NULL) ? reinterpret_cast<String*>(gThread_name->GetObject(peer_)) : NULL;
+}
+
 void Thread::DumpState(std::ostream& os) const {
   std::string thread_name("<native thread without managed peer>");
   std::string group_name;
@@ -1142,6 +1146,27 @@
   return result;
 }
 
+void Thread::GetCurrentLocation(const char*& source_file, uint32_t& line_number) const {
+  Frame f = top_of_managed_stack_;
+  Method* m = f.GetMethod();
+  // TODO: can this ever happen?
+  if (m->IsCalleeSaveMethod()) {
+    f.Next();
+    m = f.GetMethod();
+  }
+
+  ClassLinker* class_linker = Runtime::Current()->GetClassLinker();
+  Class* c = m->GetDeclaringClass();
+  DexCache* dex_cache = c->GetDexCache();
+  const DexFile& dex_file = class_linker->FindDexFile(dex_cache);
+  const DexFile::ClassDef* class_def = dex_file.FindClassDef(c->GetDescriptor()->ToModifiedUtf8());
+
+  source_file = dex_file.dexGetSourceFile(*class_def);
+
+  uint32_t pc = ManglePc(f.GetReturnPC());
+  line_number = dex_file.GetLineNumFromPC(m, m->ToDexPC(pc));
+}
+
 void Thread::ThrowNewExceptionF(const char* exception_class_descriptor, const char* fmt, ...) {
   va_list args;
   va_start(args, fmt);
diff --git a/src/thread.h b/src/thread.h
index a4e0576..ca8cb03 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -223,6 +223,12 @@
     return tid_;
   }
 
+  // Returns the java.lang.Thread's name, or NULL.
+  String* GetName() const;
+
+  // Returns the current method's declaring class' source file and the current line number.
+  void GetCurrentLocation(const char*& source_file, uint32_t& line_number) const;
+
   Object* GetPeer() const {
     return peer_;
   }