diff --git a/src/profile-handler.cc b/src/profile-handler.cc
new file mode 100644
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--- /dev/null
+++ b/src/profile-handler.cc
@@ -0,0 +1,697 @@
+// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
+// Copyright (c) 2009, Google Inc.
+// 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 with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// ---
+// Author: Sanjay Ghemawat
+//         Nabeel Mian
+//
+// Implements management of profile timers and the corresponding signal handler.
+
+#include "config.h"
+#include "profile-handler.h"
+
+#if !(defined(__CYGWIN__) || defined(__CYGWIN32__))
+
+#include <stdio.h>
+#include <errno.h>
+#include <sys/time.h>
+
+#include <list>
+#include <string>
+
+#if HAVE_LINUX_SIGEV_THREAD_ID
+// for timer_{create,settime} and associated typedefs & constants
+#include <time.h>
+// for sys_gettid
+#include "base/linux_syscall_support.h"
+// for perftools_pthread_key_create
+#include "maybe_threads.h"
+#endif
+
+#include "base/dynamic_annotations.h"
+#include "base/googleinit.h"
+#include "base/logging.h"
+#include "base/spinlock.h"
+#include "maybe_threads.h"
+
+using std::list;
+using std::string;
+
+// This structure is used by ProfileHandlerRegisterCallback and
+// ProfileHandlerUnregisterCallback as a handle to a registered callback.
+struct ProfileHandlerToken {
+  // Sets the callback and associated arg.
+  ProfileHandlerToken(ProfileHandlerCallback cb, void* cb_arg)
+      : callback(cb),
+        callback_arg(cb_arg) {
+  }
+
+  // Callback function to be invoked on receiving a profile timer interrupt.
+  ProfileHandlerCallback callback;
+  // Argument for the callback function.
+  void* callback_arg;
+};
+
+// This class manages profile timers and associated signal handler. This is a
+// a singleton.
+class ProfileHandler {
+ public:
+  // Registers the current thread with the profile handler. On systems which
+  // have a separate interval timer for each thread, this function starts the
+  // timer for the current thread.
+  //
+  // The function also attempts to determine whether or not timers are shared by
+  // all threads in the process.  (With LinuxThreads, and with NPTL on some
+  // Linux kernel versions, each thread has separate timers.)
+  //
+  // Prior to determining whether timers are shared, this function will
+  // unconditionally start the timer.  However, if this function determines
+  // that timers are shared, then it will stop the timer if no callbacks are
+  // currently registered.
+  void RegisterThread();
+
+  // Registers a callback routine to receive profile timer ticks. The returned
+  // token is to be used when unregistering this callback and must not be
+  // deleted by the caller. Registration of the first callback enables the
+  // SIGPROF handler (or SIGALRM if using ITIMER_REAL).
+  ProfileHandlerToken* RegisterCallback(ProfileHandlerCallback callback,
+                                        void* callback_arg);
+
+  // Unregisters a previously registered callback. Expects the token returned
+  // by the corresponding RegisterCallback routine. Unregistering the last
+  // callback disables the SIGPROF handler (or SIGALRM if using ITIMER_REAL).
+  void UnregisterCallback(ProfileHandlerToken* token)
+      NO_THREAD_SAFETY_ANALYSIS;
+
+  // Unregisters all the callbacks, stops the timer if shared, disables the
+  // SIGPROF (or SIGALRM) handler and clears the timer_sharing_ state.
+  void Reset();
+
+  // Gets the current state of profile handler.
+  void GetState(ProfileHandlerState* state);
+
+  // Initializes and returns the ProfileHandler singleton.
+  static ProfileHandler* Instance();
+
+ private:
+  ProfileHandler();
+  ~ProfileHandler();
+
+  // Largest allowed frequency.
+  static const int32 kMaxFrequency = 4000;
+  // Default frequency.
+  static const int32 kDefaultFrequency = 100;
+
+  // ProfileHandler singleton.
+  static ProfileHandler* instance_;
+
+  // pthread_once_t for one time initialization of ProfileHandler singleton.
+  static pthread_once_t once_;
+
+  // Initializes the ProfileHandler singleton via GoogleOnceInit.
+  static void Init();
+
+  // The number of SIGPROF (or SIGALRM for ITIMER_REAL) interrupts received.
+  int64 interrupts_ GUARDED_BY(signal_lock_);
+
+  // SIGPROF/SIGALRM interrupt frequency, read-only after construction.
+  int32 frequency_;
+
+  // ITIMER_PROF (which uses SIGPROF), or ITIMER_REAL (which uses SIGALRM)
+  int timer_type_;
+
+  // Signal number for timer signal.
+  int signal_number_;
+
+  // Counts the number of callbacks registered.
+  int32 callback_count_ GUARDED_BY(control_lock_);
+
+  // Is profiling allowed at all?
+  bool allowed_;
+
+  bool per_thread_timer_enabled_;
+
+#ifdef HAVE_LINUX_SIGEV_THREAD_ID
+  // this is used to destroy per-thread profiling timers on thread
+  // termination
+  pthread_key_t thread_timer_key;
+#endif
+
+  // Whether or not the threading system provides interval timers that are
+  // shared by all threads in a process.
+  enum {
+    // No timer initialization attempted yet.
+    TIMERS_UNTOUCHED,
+    // First thread has registered and set timer.
+    TIMERS_ONE_SET,
+    // Timers are shared by all threads.
+    TIMERS_SHARED,
+    // Timers are separate in each thread.
+    TIMERS_SEPARATE
+  } timer_sharing_ GUARDED_BY(control_lock_);
+
+  // This lock serializes the registration of threads and protects the
+  // callbacks_ list below.
+  // Locking order:
+  // In the context of a signal handler, acquire signal_lock_ to walk the
+  // callback list. Otherwise, acquire control_lock_, disable the signal
+  // handler and then acquire signal_lock_.
+  SpinLock control_lock_ ACQUIRED_BEFORE(signal_lock_);
+  SpinLock signal_lock_;
+
+  // Holds the list of registered callbacks. We expect the list to be pretty
+  // small. Currently, the cpu profiler (base/profiler) and thread module
+  // (base/thread.h) are the only two components registering callbacks.
+  // Following are the locking requirements for callbacks_:
+  // For read-write access outside the SIGPROF handler:
+  //  - Acquire control_lock_
+  //  - Disable SIGPROF handler.
+  //  - Acquire signal_lock_
+  // For read-only access in the context of SIGPROF handler
+  // (Read-write access is *not allowed* in the SIGPROF handler)
+  //  - Acquire signal_lock_
+  // For read-only access outside SIGPROF handler:
+  //  - Acquire control_lock_
+  typedef list<ProfileHandlerToken*> CallbackList;
+  typedef CallbackList::iterator CallbackIterator;
+  CallbackList callbacks_ GUARDED_BY(signal_lock_);
+
+  // Starts the interval timer.  If the thread library shares timers between
+  // threads, this function starts the shared timer. Otherwise, this will start
+  // the timer in the current thread.
+  void StartTimer() EXCLUSIVE_LOCKS_REQUIRED(control_lock_);
+
+  // Stops the interval timer. If the thread library shares timers between
+  // threads, this fucntion stops the shared timer. Otherwise, this will stop
+  // the timer in the current thread.
+  void StopTimer() EXCLUSIVE_LOCKS_REQUIRED(control_lock_);
+
+  // Returns true if the profile interval timer is enabled in the current
+  // thread.  This actually checks the kernel's interval timer setting.  (It is
+  // used to detect whether timers are shared or separate.)
+  bool IsTimerRunning() EXCLUSIVE_LOCKS_REQUIRED(control_lock_);
+
+  // Sets the timer interrupt signal handler.
+  void EnableHandler() EXCLUSIVE_LOCKS_REQUIRED(control_lock_);
+
+  // Disables (ignores) the timer interrupt signal.
+  void DisableHandler() EXCLUSIVE_LOCKS_REQUIRED(control_lock_);
+
+  // Returns true if the handler is not being used by something else.
+  // This checks the kernel's signal handler table.
+  bool IsSignalHandlerAvailable();
+
+  // SIGPROF/SIGALRM handler. Iterate over and call all the registered callbacks.
+  static void SignalHandler(int sig, siginfo_t* sinfo, void* ucontext);
+
+  DISALLOW_COPY_AND_ASSIGN(ProfileHandler);
+};
+
+ProfileHandler* ProfileHandler::instance_ = NULL;
+pthread_once_t ProfileHandler::once_ = PTHREAD_ONCE_INIT;
+
+const int32 ProfileHandler::kMaxFrequency;
+const int32 ProfileHandler::kDefaultFrequency;
+
+// If we are LD_PRELOAD-ed against a non-pthreads app, then
+// pthread_once won't be defined.  We declare it here, for that
+// case (with weak linkage) which will cause the non-definition to
+// resolve to NULL.  We can then check for NULL or not in Instance.
+extern "C" int pthread_once(pthread_once_t *, void (*)(void))
+    ATTRIBUTE_WEAK;
+
+#if HAVE_LINUX_SIGEV_THREAD_ID
+
+// We use weak alias to timer_create to avoid runtime dependency on
+// -lrt and in turn -lpthread.
+//
+// At runtime we detect if timer_create is available and if so we
+// can enable linux-sigev-thread mode of profiling
+extern "C" {
+  int timer_create(clockid_t clockid, struct sigevent *evp,
+                            timer_t *timerid)
+    ATTRIBUTE_WEAK;
+  int timer_delete(timer_t timerid)
+    ATTRIBUTE_WEAK;
+  int timer_settime(timer_t timerid, int flags,
+                    const struct itimerspec *value,
+                    struct itimerspec *ovalue)
+    ATTRIBUTE_WEAK;
+}
+
+struct timer_id_holder {
+  timer_t timerid;
+  timer_id_holder(timer_t _timerid) : timerid(_timerid) {}
+};
+
+extern "C" {
+  static void ThreadTimerDestructor(void *arg) {
+    if (!arg) {
+      return;
+    }
+    timer_id_holder *holder = static_cast<timer_id_holder *>(arg);
+    timer_delete(holder->timerid);
+    delete holder;
+  }
+}
+
+static void CreateThreadTimerKey(pthread_key_t *pkey) {
+  int rv = perftools_pthread_key_create(pkey, ThreadTimerDestructor);
+  if (rv) {
+    RAW_LOG(FATAL, "aborting due to pthread_key_create error: %s", strerror(rv));
+  }
+}
+
+static void StartLinuxThreadTimer(int timer_type, int signal_number,
+                                  int32 frequency, pthread_key_t timer_key) {
+  int rv;
+  struct sigevent sevp;
+  timer_t timerid;
+  struct itimerspec its;
+  memset(&sevp, 0, sizeof(sevp));
+  sevp.sigev_notify = SIGEV_THREAD_ID;
+  sevp._sigev_un._tid = sys_gettid();
+  sevp.sigev_signo = signal_number;
+  clockid_t clock = CLOCK_THREAD_CPUTIME_ID;
+  if (timer_type == ITIMER_REAL) {
+    clock = CLOCK_MONOTONIC;
+  }
+  rv = timer_create(clock, &sevp, &timerid);
+  if (rv) {
+    RAW_LOG(FATAL, "aborting due to timer_create error: %s", strerror(errno));
+  }
+
+  timer_id_holder *holder = new timer_id_holder(timerid);
+  rv = perftools_pthread_setspecific(timer_key, holder);
+  if (rv) {
+    RAW_LOG(FATAL, "aborting due to pthread_setspecific error: %s", strerror(rv));
+  }
+
+  its.it_interval.tv_sec = 0;
+  its.it_interval.tv_nsec = 1000000000 / frequency;
+  its.it_value = its.it_interval;
+  rv = timer_settime(timerid, 0, &its, 0);
+  if (rv) {
+    RAW_LOG(FATAL, "aborting due to timer_settime error: %s", strerror(errno));
+  }
+}
+#endif
+
+void ProfileHandler::Init() {
+  instance_ = new ProfileHandler();
+}
+
+ProfileHandler* ProfileHandler::Instance() {
+  if (pthread_once) {
+    pthread_once(&once_, Init);
+  }
+  if (instance_ == NULL) {
+    // This will be true on systems that don't link in pthreads,
+    // including on FreeBSD where pthread_once has a non-zero address
+    // (but doesn't do anything) even when pthreads isn't linked in.
+    Init();
+    assert(instance_ != NULL);
+  }
+  return instance_;
+}
+
+ProfileHandler::ProfileHandler()
+    : interrupts_(0),
+      callback_count_(0),
+      allowed_(true),
+      per_thread_timer_enabled_(false),
+      timer_sharing_(TIMERS_UNTOUCHED) {
+  SpinLockHolder cl(&control_lock_);
+
+  timer_type_ = (getenv("CPUPROFILE_REALTIME") ? ITIMER_REAL : ITIMER_PROF);
+  signal_number_ = (timer_type_ == ITIMER_PROF ? SIGPROF : SIGALRM);
+
+  // Get frequency of interrupts (if specified)
+  char junk;
+  const char* fr = getenv("CPUPROFILE_FREQUENCY");
+  if (fr != NULL && (sscanf(fr, "%u%c", &frequency_, &junk) == 1) &&
+      (frequency_ > 0)) {
+    // Limit to kMaxFrequency
+    frequency_ = (frequency_ > kMaxFrequency) ? kMaxFrequency : frequency_;
+  } else {
+    frequency_ = kDefaultFrequency;
+  }
+
+  if (!allowed_) {
+    return;
+  }
+
+#if HAVE_LINUX_SIGEV_THREAD_ID
+  // Do this early because we might be overriding signal number.
+
+  const char *per_thread = getenv("CPUPROFILE_PER_THREAD_TIMERS");
+  const char *signal_number = getenv("CPUPROFILE_TIMER_SIGNAL");
+
+  if (per_thread || signal_number) {
+    if (timer_create && pthread_once) {
+      timer_sharing_ = TIMERS_SEPARATE;
+      CreateThreadTimerKey(&thread_timer_key);
+      per_thread_timer_enabled_ = true;
+      // Override signal number if requested.
+      if (signal_number) {
+        signal_number_ = strtol(signal_number, NULL, 0);
+      }
+    } else {
+      RAW_LOG(INFO,
+              "Ignoring CPUPROFILE_PER_THREAD_TIMERS and\n"
+              " CPUPROFILE_TIMER_SIGNAL due to lack of timer_create().\n"
+              " Preload or link to librt.so for this to work");
+    }
+  }
+#endif
+
+  // If something else is using the signal handler,
+  // assume it has priority over us and stop.
+  if (!IsSignalHandlerAvailable()) {
+    RAW_LOG(INFO, "Disabling profiler because signal %d handler is already in use.",
+            signal_number_);
+    allowed_ = false;
+    return;
+  }
+
+  // Ignore signals until we decide to turn profiling on.  (Paranoia;
+  // should already be ignored.)
+  DisableHandler();
+
+}
+
+ProfileHandler::~ProfileHandler() {
+  Reset();
+#ifdef HAVE_LINUX_SIGEV_THREAD_ID
+  if (per_thread_timer_enabled_) {
+    perftools_pthread_key_delete(thread_timer_key);
+  }
+#endif
+}
+
+void ProfileHandler::RegisterThread() {
+  SpinLockHolder cl(&control_lock_);
+
+  if (!allowed_) {
+    return;
+  }
+
+  // We try to detect whether timers are being shared by setting a
+  // timer in the first call to this function, then checking whether
+  // it's set in the second call.
+  //
+  // Note that this detection method requires that the first two calls
+  // to RegisterThread must be made from different threads.  (Subsequent
+  // calls will see timer_sharing_ set to either TIMERS_SEPARATE or
+  // TIMERS_SHARED, and won't try to detect the timer sharing type.)
+  //
+  // Also note that if timer settings were inherited across new thread
+  // creation but *not* shared, this approach wouldn't work.  That's
+  // not an issue for any Linux threading implementation, and should
+  // not be a problem for a POSIX-compliant threads implementation.
+  switch (timer_sharing_) {
+    case TIMERS_UNTOUCHED:
+      StartTimer();
+      timer_sharing_ = TIMERS_ONE_SET;
+      break;
+    case TIMERS_ONE_SET:
+      // If the timer is running, that means that the main thread's
+      // timer setup is seen in this (second) thread -- and therefore
+      // that timers are shared.
+      if (IsTimerRunning()) {
+        timer_sharing_ = TIMERS_SHARED;
+        // If callback is already registered, we have to keep the timer
+        // running.  If not, we disable the timer here.
+        if (callback_count_ == 0) {
+          StopTimer();
+        }
+      } else {
+        timer_sharing_ = TIMERS_SEPARATE;
+        StartTimer();
+      }
+      break;
+    case TIMERS_SHARED:
+      // Nothing needed.
+      break;
+    case TIMERS_SEPARATE:
+      StartTimer();
+      break;
+  }
+}
+
+ProfileHandlerToken* ProfileHandler::RegisterCallback(
+    ProfileHandlerCallback callback, void* callback_arg) {
+
+  ProfileHandlerToken* token = new ProfileHandlerToken(callback, callback_arg);
+
+  SpinLockHolder cl(&control_lock_);
+  DisableHandler();
+  {
+    SpinLockHolder sl(&signal_lock_);
+    callbacks_.push_back(token);
+  }
+  // Start the timer if timer is shared and this is a first callback.
+  if ((callback_count_ == 0) && (timer_sharing_ == TIMERS_SHARED)) {
+    StartTimer();
+  }
+  ++callback_count_;
+  EnableHandler();
+  return token;
+}
+
+void ProfileHandler::UnregisterCallback(ProfileHandlerToken* token) {
+  SpinLockHolder cl(&control_lock_);
+  for (CallbackIterator it = callbacks_.begin(); it != callbacks_.end();
+       ++it) {
+    if ((*it) == token) {
+      RAW_CHECK(callback_count_ > 0, "Invalid callback count");
+      DisableHandler();
+      {
+        SpinLockHolder sl(&signal_lock_);
+        delete *it;
+        callbacks_.erase(it);
+      }
+      --callback_count_;
+      if (callback_count_ > 0) {
+        EnableHandler();
+      } else if (timer_sharing_ == TIMERS_SHARED) {
+        StopTimer();
+      }
+      return;
+    }
+  }
+  // Unknown token.
+  RAW_LOG(FATAL, "Invalid token");
+}
+
+void ProfileHandler::Reset() {
+  SpinLockHolder cl(&control_lock_);
+  DisableHandler();
+  {
+    SpinLockHolder sl(&signal_lock_);
+    CallbackIterator it = callbacks_.begin();
+    while (it != callbacks_.end()) {
+      CallbackIterator tmp = it;
+      ++it;
+      delete *tmp;
+      callbacks_.erase(tmp);
+    }
+  }
+  callback_count_ = 0;
+  if (timer_sharing_ == TIMERS_SHARED) {
+    StopTimer();
+  }
+  timer_sharing_ = TIMERS_UNTOUCHED;
+}
+
+void ProfileHandler::GetState(ProfileHandlerState* state) {
+  SpinLockHolder cl(&control_lock_);
+  DisableHandler();
+  {
+    SpinLockHolder sl(&signal_lock_);  // Protects interrupts_.
+    state->interrupts = interrupts_;
+  }
+  if (callback_count_ > 0) {
+    EnableHandler();
+  }
+  state->frequency = frequency_;
+  state->callback_count = callback_count_;
+  state->allowed = allowed_;
+}
+
+void ProfileHandler::StartTimer() {
+  if (!allowed_) {
+    return;
+  }
+
+#if HAVE_LINUX_SIGEV_THREAD_ID
+  if (per_thread_timer_enabled_) {
+    StartLinuxThreadTimer(timer_type_, signal_number_, frequency_, thread_timer_key);
+    return;
+  }
+#endif
+
+  struct itimerval timer;
+  timer.it_interval.tv_sec = 0;
+  timer.it_interval.tv_usec = 1000000 / frequency_;
+  timer.it_value = timer.it_interval;
+  setitimer(timer_type_, &timer, 0);
+}
+
+void ProfileHandler::StopTimer() {
+  if (!allowed_) {
+    return;
+  }
+  if (per_thread_timer_enabled_) {
+    RAW_LOG(FATAL, "StopTimer cannot be called in linux-per-thread-timers mode");
+  }
+
+  struct itimerval timer;
+  memset(&timer, 0, sizeof timer);
+  setitimer(timer_type_, &timer, 0);
+}
+
+bool ProfileHandler::IsTimerRunning() {
+  if (!allowed_) {
+    return false;
+  }
+  if (per_thread_timer_enabled_) {
+    return false;
+  }
+  struct itimerval current_timer;
+  RAW_CHECK(0 == getitimer(timer_type_, &current_timer), "getitimer");
+  return (current_timer.it_value.tv_sec != 0 ||
+          current_timer.it_value.tv_usec != 0);
+}
+
+void ProfileHandler::EnableHandler() {
+  if (!allowed_) {
+    return;
+  }
+  struct sigaction sa;
+  sa.sa_sigaction = SignalHandler;
+  sa.sa_flags = SA_RESTART | SA_SIGINFO;
+  sigemptyset(&sa.sa_mask);
+  RAW_CHECK(sigaction(signal_number_, &sa, NULL) == 0, "sigprof (enable)");
+}
+
+void ProfileHandler::DisableHandler() {
+  if (!allowed_) {
+    return;
+  }
+  struct sigaction sa;
+  sa.sa_handler = SIG_IGN;
+  sa.sa_flags = SA_RESTART;
+  sigemptyset(&sa.sa_mask);
+  RAW_CHECK(sigaction(signal_number_, &sa, NULL) == 0, "sigprof (disable)");
+}
+
+bool ProfileHandler::IsSignalHandlerAvailable() {
+  struct sigaction sa;
+  RAW_CHECK(sigaction(signal_number_, NULL, &sa) == 0, "is-signal-handler avail");
+
+  // We only take over the handler if the current one is unset.
+  // It must be SIG_IGN or SIG_DFL, not some other function.
+  // SIG_IGN must be allowed because when profiling is allowed but
+  // not actively in use, this code keeps the handler set to SIG_IGN.
+  // That setting will be inherited across fork+exec.  In order for
+  // any child to be able to use profiling, SIG_IGN must be treated
+  // as available.
+  return sa.sa_handler == SIG_IGN || sa.sa_handler == SIG_DFL;
+}
+
+void ProfileHandler::SignalHandler(int sig, siginfo_t* sinfo, void* ucontext) {
+  int saved_errno = errno;
+  // At this moment, instance_ must be initialized because the handler is
+  // enabled in RegisterThread or RegisterCallback only after
+  // ProfileHandler::Instance runs.
+  ProfileHandler* instance = ANNOTATE_UNPROTECTED_READ(instance_);
+  RAW_CHECK(instance != NULL, "ProfileHandler is not initialized");
+  {
+    SpinLockHolder sl(&instance->signal_lock_);
+    ++instance->interrupts_;
+    for (CallbackIterator it = instance->callbacks_.begin();
+         it != instance->callbacks_.end();
+         ++it) {
+      (*it)->callback(sig, sinfo, ucontext, (*it)->callback_arg);
+    }
+  }
+  errno = saved_errno;
+}
+
+// This module initializer registers the main thread, so it must be
+// executed in the context of the main thread.
+REGISTER_MODULE_INITIALIZER(profile_main, ProfileHandlerRegisterThread());
+
+extern "C" void ProfileHandlerRegisterThread() {
+  ProfileHandler::Instance()->RegisterThread();
+}
+
+extern "C" ProfileHandlerToken* ProfileHandlerRegisterCallback(
+    ProfileHandlerCallback callback, void* callback_arg) {
+  return ProfileHandler::Instance()->RegisterCallback(callback, callback_arg);
+}
+
+extern "C" void ProfileHandlerUnregisterCallback(ProfileHandlerToken* token) {
+  ProfileHandler::Instance()->UnregisterCallback(token);
+}
+
+extern "C" void ProfileHandlerReset() {
+  return ProfileHandler::Instance()->Reset();
+}
+
+extern "C" void ProfileHandlerGetState(ProfileHandlerState* state) {
+  ProfileHandler::Instance()->GetState(state);
+}
+
+#else  // OS_CYGWIN
+
+// ITIMER_PROF doesn't work under cygwin.  ITIMER_REAL is available, but doesn't
+// work as well for profiling, and also interferes with alarm().  Because of
+// these issues, unless a specific need is identified, profiler support is
+// disabled under Cygwin.
+extern "C" void ProfileHandlerRegisterThread() {
+}
+
+extern "C" ProfileHandlerToken* ProfileHandlerRegisterCallback(
+    ProfileHandlerCallback callback, void* callback_arg) {
+  return NULL;
+}
+
+extern "C" void ProfileHandlerUnregisterCallback(ProfileHandlerToken* token) {
+}
+
+extern "C" void ProfileHandlerReset() {
+}
+
+extern "C" void ProfileHandlerGetState(ProfileHandlerState* state) {
+}
+
+#endif  // OS_CYGWIN