# HG changeset patch
# User igerasim
# Date 1468699800 -10800
# Node ID b86bebb34220c4c8ae2fa905040151a6f1b6477e
# Parent  44f83dd02bd57819c7ae27d305a45339c65cc312
8160892: Race at the VM exit causes "WaitForMultipleObjects timed out"
Reviewed-by: dcubed, dholmes

diff -r 44f83dd02bd5 -r b86bebb34220 hotspot/src/os/windows/vm/os_windows.cpp
--- a/hotspot/src/os/windows/vm/os_windows.cpp	Fri Jul 15 17:05:10 2016 -0700
+++ b/hotspot/src/os/windows/vm/os_windows.cpp	Sat Jul 16 23:10:00 2016 +0300
@@ -3898,6 +3898,13 @@
     DWORD res;
     HANDLE hproc, hthr;
 
+    // We only attempt to register threads until a process exiting
+    // thread manages to set the process_exiting flag. Any threads
+    // that come through here after the process_exiting flag is set
+    // are unregistered and will be caught in the SuspendThread()
+    // infinite loop below.
+    bool registered = false;
+
     // The first thread that reached this point, initializes the critical section.
     if (!InitOnceExecuteOnce(&init_once_crit_sect, init_crit_sect_call, &crit_sect, NULL)) {
       warning("crit_sect initialization failed in %s: %d\n", __FILE__, __LINE__);
@@ -3957,13 +3964,22 @@
                              0, FALSE, DUPLICATE_SAME_ACCESS)) {
           warning("DuplicateHandle failed (%u) in %s: %d\n",
                   GetLastError(), __FILE__, __LINE__);
+
+          // We can't register this thread (no more handles) so this thread
+          // may be racing with a thread that is calling exit(). If the thread
+          // that is calling exit() has managed to set the process_exiting
+          // flag, then this thread will be caught in the SuspendThread()
+          // infinite loop below which closes that race. A small timing
+          // window remains before the process_exiting flag is set, but it
+          // is only exposed when we are out of handles.
         } else {
           ++handle_count;
+          registered = true;
+
+          // The current exiting thread has stored its handle in the array, and now
+          // should leave the critical section before calling _endthreadex().
         }
 
-        // The current exiting thread has stored its handle in the array, and now
-        // should leave the critical section before calling _endthreadex().
-
       } else if (what != EPT_THREAD && handle_count > 0) {
         jlong start_time, finish_time, timeout_left;
         // Before ending the process, make sure all the threads that had called
@@ -4012,10 +4028,11 @@
       LeaveCriticalSection(&crit_sect);
     }
 
-    if (OrderAccess::load_acquire(&process_exiting) != 0 &&
+    if (!registered &&
+        OrderAccess::load_acquire(&process_exiting) != 0 &&
         process_exiting != (jint)GetCurrentThreadId()) {
-      // Some other thread is about to call exit(), so we
-      // don't let the current thread proceed to exit() or _endthreadex()
+      // Some other thread is about to call exit(), so we don't let
+      // the current unregistered thread proceed to exit() or _endthreadex()
       while (true) {
         SuspendThread(GetCurrentThread());
         // Avoid busy-wait loop, if SuspendThread() failed.
@@ -4027,7 +4044,7 @@
   // We are here if either
   // - there's no 'race at exit' bug on this OS release;
   // - initialization of the critical section failed (unlikely);
-  // - the current thread has stored its handle and left the critical section;
+  // - the current thread has registered itself and left the critical section;
   // - the process-exiting thread has raised the flag and left the critical section.
   if (what == EPT_THREAD) {
     _endthreadex((unsigned)exit_code);