From a4a62971906a31fc6e7f6bd2f7058188a8a16db5 Mon Sep 17 00:00:00 2001
From: ysr <unknown>
Date: Mon, 13 Jun 2011 09:58:16 -0700
Subject: [PATCH] 7051430: CMS: ongoing CMS cycle should terminate abruptly to
 allow prompt JVM termination at exit Summary: It turns out that there is no
 need to explicitly stop CMS since the JVM is taken down at a terminal
 safepoint during which CMS threads are (terminally) inactive. This  will need
 to be revised if and when we evolve in the future to a point where we allow
 JVM reincarnation in the same process, but those changes will be much more
 sweeping than just terminating CMS threads. The unused ::stop() methods will
 be removed in a separate CR. Also include in this CR is the fix for a small
 typo in the spelling of UseGCLogFileRotation in a message in arguments.cpp,
 brought to our attention by Rainer Jung and reviewed by minqi. Reviewed-by:
 johnc, jwilhelm

---
 src/share/vm/runtime/arguments.cpp |  2 +-
 src/share/vm/runtime/java.cpp      | 10 ++++------
 src/share/vm/runtime/thread.cpp    |  8 ++++++++
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/share/vm/runtime/arguments.cpp b/src/share/vm/runtime/arguments.cpp
index 4ebfea446..14dbcb72e 100644
--- a/src/share/vm/runtime/arguments.cpp
+++ b/src/share/vm/runtime/arguments.cpp
@@ -1690,7 +1690,7 @@ void check_gclog_consistency() {
         (NumberOfGCLogFiles == 0)  ||
         (GCLogFileSize == 0)) {
       jio_fprintf(defaultStream::output_stream(),
-                  "To enable GC log rotation, use -Xloggc:<filename> -XX:+UseGCLogRotaion -XX:NumberOfGCLogFiles=<num_of_files> -XX:GCLogFileSize=<num_of_size>\n"
+                  "To enable GC log rotation, use -Xloggc:<filename> -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=<num_of_files> -XX:GCLogFileSize=<num_of_size>\n"
                   "where num_of_file > 0 and num_of_size > 0\n"
                   "GC log rotation is turned off\n");
       UseGCLogFileRotation = false;
diff --git a/src/share/vm/runtime/java.cpp b/src/share/vm/runtime/java.cpp
index c415016f8..73065fe42 100644
--- a/src/share/vm/runtime/java.cpp
+++ b/src/share/vm/runtime/java.cpp
@@ -468,12 +468,10 @@ void before_exit(JavaThread * thread) {
   StatSampler::disengage();
   StatSampler::destroy();
 
-#ifndef SERIALGC
-  // stop CMS threads
-  if (UseConcMarkSweepGC) {
-    ConcurrentMarkSweepThread::stop();
-  }
-#endif // SERIALGC
+  // We do not need to explicitly stop concurrent GC threads because the
+  // JVM will be taken down at a safepoint when such threads are inactive --
+  // except for some concurrent G1 threads, see (comment in)
+  // Threads::destroy_vm().
 
   // Print GC/heap related information.
   if (PrintGCDetails) {
diff --git a/src/share/vm/runtime/thread.cpp b/src/share/vm/runtime/thread.cpp
index 97b55ead1..72a3f51f9 100644
--- a/src/share/vm/runtime/thread.cpp
+++ b/src/share/vm/runtime/thread.cpp
@@ -3698,6 +3698,14 @@ bool Threads::destroy_vm() {
     // heap is unparseable if they are caught. Grab the Heap_lock
     // to prevent this. The GC vm_operations will not be able to
     // queue until after the vm thread is dead.
+    // After this point, we'll never emerge out of the safepoint before
+    // the VM exits, so concurrent GC threads do not need to be explicitly
+    // stopped; they remain inactive until the process exits.
+    // Note: some concurrent G1 threads may be running during a safepoint,
+    // but these will not be accessing the heap, just some G1-specific side
+    // data structures that are not accessed by any other threads but them
+    // after this point in a terminal safepoint.
+
     MutexLocker ml(Heap_lock);
 
     VMThread::wait_for_vm_thread_exit();
-- 
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