--- a/hotspot/src/os/bsd/vm/os_bsd.cpp	Thu Aug 31 17:06:10 2017 +0000
+++ b/hotspot/src/os/bsd/vm/os_bsd.cpp	Thu Aug 31 20:26:53 2017 -0500
@@ -2603,11 +2603,10 @@
 ////////////////////////////////////////////////////////////////////////////////
 // suspend/resume support
 
-//  the low-level signal-based suspend/resume support is a remnant from the
+//  The low-level signal-based suspend/resume support is a remnant from the
 //  old VM-suspension that used to be for java-suspension, safepoints etc,
-//  within hotspot. Now there is a single use-case for this:
-//    - calling get_thread_pc() on the VMThread by the flat-profiler task
-//      that runs in the watcher thread.
+//  within hotspot. Currently used by JFR's OSThreadSampler
+//
 //  The remaining code is greatly simplified from the more general suspension
 //  code that used to be used.
 //
@@ -2623,6 +2622,13 @@
 //
 //  Note that the SR_lock plays no role in this suspend/resume protocol,
 //  but is checked for NULL in SR_handler as a thread termination indicator.
+//  The SR_lock is, however, used by JavaThread::java_suspend()/java_resume() APIs.
+//
+//  Note that resume_clear_context() and suspend_save_context() are needed
+//  by SR_handler(), so that fetch_frame_from_ucontext() works,
+//  which in part is used by:
+//    - Forte Analyzer: AsyncGetCallTrace()
+//    - StackBanging: get_frame_at_stack_banging_point()
 
 static void resume_clear_context(OSThread *osthread) {
   osthread->set_ucontext(NULL);
@@ -3521,45 +3527,6 @@
   }
 }
 
-///
-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::Bsd::ucontext_get_pc((const 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) {
-  // Make sure that it is called by the watcher for the VMThread
-  assert(Thread::current()->is_Watcher_thread(), "Must be watcher");
-  assert(thread->is_VM_thread(), "Can only be called for VMThread");
-
-  PcFetcher fetcher(thread);
-  fetcher.run();
-  return fetcher.result();
-}
-
 ////////////////////////////////////////////////////////////////////////////////
 // debug support