--- old/src/os/linux/vm/os_linux.cpp	2013-06-05 10:55:25.000000000 +0200
+++ new/src/os/linux/vm/os_linux.cpp	2013-06-05 10:55:25.000000000 +0200
@@ -145,6 +145,9 @@
 /* Used to protect dlsym() calls */
 static pthread_mutex_t dl_mutex;
 
+// Declarations
+static void unpackTime(timespec* absTime, bool isAbsolute, jlong time);
+
 #ifdef JAVASE_EMBEDDED
 class MemNotifyThread: public Thread {
   friend class VMStructs;
@@ -2397,6 +2400,57 @@
   return CAST_FROM_FN_PTR(void*, UserHandler);
 }
 
+class Semaphore : public StackObj {
+  public:
+    Semaphore();
+    ~Semaphore();
+    void signal();
+    void wait();
+    bool trywait();
+    bool timedwait(unsigned int sec, int nsec);
+  private:
+    sem_t _semaphore;
+};
+
+
+Semaphore::Semaphore() {
+  sem_init(&_semaphore, 0, 0);
+}
+
+Semaphore::~Semaphore() {
+  sem_destroy(&_semaphore);
+}
+
+void Semaphore::signal() {
+  sem_post(&_semaphore);
+}
+
+void Semaphore::wait() {
+  sem_wait(&_semaphore);
+}
+
+bool Semaphore::trywait() {
+  return sem_trywait(&_semaphore) == 0;
+}
+
+bool Semaphore::timedwait(unsigned int sec, int nsec) {
+  struct timespec ts;
+  unpackTime(&ts, false, (sec * NANOSECS_PER_SEC) + nsec);
+
+  while (1) {
+    int result = sem_timedwait(&_semaphore, &ts);
+    if (result == 0) {
+      return true;
+    } else if (errno == EINTR) {
+      continue;
+    } else if (errno == ETIMEDOUT) {
+      return false;
+    } else {
+      return false;
+    }
+  }
+}
+
 extern "C" {
   typedef void (*sa_handler_t)(int);
   typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
@@ -2436,6 +2490,7 @@
 
 // Linux(POSIX) specific hand shaking semaphore.
 static sem_t sig_sem;
+static Semaphore sr_semaphore;
 
 void os::signal_init_pd() {
   // Initialize signal structures
@@ -3549,9 +3604,6 @@
 static void resume_clear_context(OSThread *osthread) {
   osthread->set_ucontext(NULL);
   osthread->set_siginfo(NULL);
-
-  // notify the suspend action is completed, we have now resumed
-  osthread->sr.clear_suspended();
 }
 
 static void suspend_save_context(OSThread *osthread, siginfo_t* siginfo, ucontext_t* context) {
@@ -3571,7 +3623,7 @@
 // its signal handlers run and prevents sigwait()'s use with the
 // mutex granting granting signal.
 //
-// Currently only ever called on the VMThread
+// Currently only ever called on the VMThread and JavaThreads (PC sampling)
 //
 static void SR_handler(int sig, siginfo_t* siginfo, ucontext_t* context) {
   // Save and restore errno to avoid confusing native code with EINTR
@@ -3580,38 +3632,46 @@
 
   Thread* thread = Thread::current();
   OSThread* osthread = thread->osthread();
-  assert(thread->is_VM_thread(), "Must be VMThread");
-  // read current suspend action
-  int action = osthread->sr.suspend_action();
-  if (action == os::Linux::SuspendResume::SR_SUSPEND) {
+  assert(thread->is_VM_thread() || thread->is_Java_thread(), "Must be VMThread or JavaThread");
+
+  os::SuspendResume::State current = osthread->sr.state();
+  if (current == os::SuspendResume::SR_SUSPEND_REQUEST) {
     suspend_save_context(osthread, siginfo, context);
 
-    // Notify the suspend action is about to be completed. do_suspend()
-    // waits until SR_SUSPENDED is set and then returns. We will wait
-    // here for a resume signal and that completes the suspend-other
-    // action. do_suspend/do_resume is always called as a pair from
-    // the same thread - so there are no races
-
-    // notify the caller
-    osthread->sr.set_suspended();
-
-    sigset_t suspend_set;  // signals for sigsuspend()
-
-    // get current set of blocked signals and unblock resume signal
-    pthread_sigmask(SIG_BLOCK, NULL, &suspend_set);
-    sigdelset(&suspend_set, SR_signum);
+    // attempt to switch the state, we assume we had a SUSPEND_REQUEST
+    os::SuspendResume::State state = osthread->sr.suspended();
+    if (state == os::SuspendResume::SR_SUSPENDED) {
+      sigset_t suspend_set;  // signals for sigsuspend()
+
+      // get current set of blocked signals and unblock resume signal
+      pthread_sigmask(SIG_BLOCK, NULL, &suspend_set);
+      sigdelset(&suspend_set, SR_signum);
+
+      sr_semaphore.signal();
+      // wait here until we are resumed
+      while (1) {
+        sigsuspend(&suspend_set);
+
+        os::SuspendResume::State result = osthread->sr.running();
+        if (result == os::SuspendResume::SR_RUNNING) {
+          sr_semaphore.signal();
+          break;
+        }
+      }
 
-    // wait here until we are resumed
-    do {
-      sigsuspend(&suspend_set);
-      // ignore all returns until we get a resume signal
-    } while (osthread->sr.suspend_action() != os::Linux::SuspendResume::SR_CONTINUE);
+    } else if (state == os::SuspendResume::SR_RUNNING) {
+      // request was cancelled, continue
+    } else {
+      ShouldNotReachHere();
+    }
 
     resume_clear_context(osthread);
-
+  } else if (current == os::SuspendResume::SR_RUNNING) {
+    // request was cancelled, continue
+  } else if (current == os::SuspendResume::SR_WAKEUP_REQUEST) {
+    // ignore
   } else {
-    assert(action == os::Linux::SuspendResume::SR_CONTINUE, "unexpected sr action");
-    // nothing special to do - just leave the handler
+    // ignore
   }
 
   errno = old_errno;
@@ -3655,42 +3715,82 @@
   return 0;
 }
 
+static int sr_notify(OSThread* osthread) {
+  int status = pthread_kill(osthread->pthread_id(), SR_signum);
+  assert_status(status == 0, status, "pthread_kill");
+  return status;
+}
+
+// "Randomly" selected value for how long we want to spin
+// before bailing out on suspending a thread, also how often
+// we send a signal to a thread we want to resume
+static const int RANDOMLY_LARGE_INTEGER = 1000000;
+static const int RANDOMLY_LARGE_INTEGER2 = 100;
 
 // returns true on success and false on error - really an error is fatal
 // but this seems the normal response to library errors
 static bool do_suspend(OSThread* osthread) {
+  assert(osthread->sr.is_running(), "thread should be running");
+  assert(!sr_semaphore.trywait(), "semaphore has invalid state");
+
   // mark as suspended and send signal
-  osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_SUSPEND);
-  int status = pthread_kill(osthread->pthread_id(), SR_signum);
-  assert_status(status == 0, status, "pthread_kill");
+  if (osthread->sr.request_suspend() != os::SuspendResume::SR_SUSPEND_REQUEST) {
+    // failed to switch, state wasn't running?
+    ShouldNotReachHere();
+    return false;
+  }
 
-  // check status and wait until notified of suspension
-  if (status == 0) {
-    for (int i = 0; !osthread->sr.is_suspended(); i++) {
-      os::yield_all(i);
-    }
-    osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_NONE);
-    return true;
+  if (sr_notify(osthread) != 0) {
+    ShouldNotReachHere();
   }
-  else {
-    osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_NONE);
-    return false;
+
+  // managed to send the signal and switch to SUSPEND_REQUEST, now wait for SUSPENDED
+  while (true) {
+    if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
+      break;
+    } else {
+      // timeout
+      os::SuspendResume::State cancelled = osthread->sr.cancel_suspend();
+      if (cancelled == os::SuspendResume::SR_RUNNING) {
+        return false;
+      } else if (cancelled == os::SuspendResume::SR_SUSPENDED) {
+        // make sure that we consume the signal on the semaphore as well
+        sr_semaphore.wait();
+        break;
+      } else {
+        ShouldNotReachHere();
+        return false;
+      }
+    }
   }
+
+  guarantee(osthread->sr.is_suspended(), "Must be suspended");
+  return true;
 }
 
 static void do_resume(OSThread* osthread) {
   assert(osthread->sr.is_suspended(), "thread should be suspended");
-  osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_CONTINUE);
+  assert(!sr_semaphore.trywait(), "invalid semaphore state");
 
-  int status = pthread_kill(osthread->pthread_id(), SR_signum);
-  assert_status(status == 0, status, "pthread_kill");
-  // check status and wait unit notified of resumption
-  if (status == 0) {
-    for (int i = 0; osthread->sr.is_suspended(); i++) {
-      os::yield_all(i);
+  if (osthread->sr.request_wakeup() != os::SuspendResume::SR_WAKEUP_REQUEST) {
+    // failed to switch to WAKEUP_REQUEST
+    ShouldNotReachHere();
+    return;
+  }
+
+  while (true) {
+    if (sr_notify(osthread) == 0) {
+      if (sr_semaphore.timedwait(0, 2 * NANOSECS_PER_MILLISEC)) {
+        if (osthread->sr.is_running()) {
+          return;
+        }
+      }
+    } else {
+      ShouldNotReachHere();
     }
   }
-  osthread->sr.set_suspend_action(os::Linux::SuspendResume::SR_NONE);
+
+  guarantee(osthread->sr.is_running(), "Must be running!");
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -4462,6 +4562,40 @@
 
 ///
 
+void os::SuspendedThreadTask::internal_do_task() {
+  if (do_suspend(_thread->osthread())) {
+    SuspendedThreadTaskContext context(_thread, _thread->osthread()->ucontext());
+    do_task(context);
+    do_resume(_thread->osthread());
+  }
+}
+
+class PcFetcher : public os::SuspendedThreadTask {
+public:
+  PcFetcher(Thread* thread) : os::SuspendedThreadTask(thread) {}
+  ExtendedPC result();
+protected:
+  void do_task(const os::SuspendedThreadTaskContext& context);
+private:
+  ExtendedPC _epc;
+};
+
+ExtendedPC PcFetcher::result() {
+  guarantee(is_done(), "task is not done yet.");
+  return _epc;
+}
+
+void PcFetcher::do_task(const os::SuspendedThreadTaskContext& context) {
+  Thread* thread = context.thread();
+  OSThread* osthread = thread->osthread();
+  if (osthread->ucontext() != NULL) {
+    _epc = os::Linux::ucontext_get_pc((ucontext_t *) context.ucontext());
+  } else {
+    // NULL context is unexpected, double-check this is the VMThread
+    guarantee(thread->is_VM_thread(), "can only be called for VMThread");
+  }
+}
+
 // Suspends the target using the signal mechanism and then grabs the PC before
 // resuming the target. Used by the flat-profiler only
 ExtendedPC os::get_thread_pc(Thread* thread) {
@@ -4469,22 +4603,9 @@
   assert(Thread::current()->is_Watcher_thread(), "Must be watcher");
   assert(thread->is_VM_thread(), "Can only be called for VMThread");
 
-  ExtendedPC epc;
-
-  OSThread* osthread = thread->osthread();
-  if (do_suspend(osthread)) {
-    if (osthread->ucontext() != NULL) {
-      epc = os::Linux::ucontext_get_pc(osthread->ucontext());
-    } else {
-      // NULL context is unexpected, double-check this is the VMThread
-      guarantee(thread->is_VM_thread(), "can only be called for VMThread");
-    }
-    do_resume(osthread);
-  }
-  // failure means pthread_kill failed for some reason - arguably this is
-  // a fatal problem, but such problems are ignored elsewhere
-
-  return epc;
+  PcFetcher fetcher(thread);
+  fetcher.run();
+  return fetcher.result();
 }
 
 int os::Linux::safe_cond_timedwait(pthread_cond_t *_cond, pthread_mutex_t *_mutex, const struct timespec *_abstime)
@@ -5606,4 +5727,5 @@
     new MemNotifyThread(fd);
   }
 }
+
 #endif // JAVASE_EMBEDDED