RFR(T) 8221643: Tighten up assert(_keep_alive >= 0) in CLD::inc_keep_alive

[Zhengyu Gu]

I would like to restore the assertion to its original form, cause the 
current form suggests the possibility of resurrection not kept alive CLD.

The current form was a workaround introduced by JDK-8162553, when null 
class loader data had keep_alive value of 0. Now, the value is 
initialized to 1 by CLD constructor, so the workaround is not needed.


diff -r f0fec71d2fff -r d023b009df71 
src/hotspot/share/classfile/classLoaderData.cpp
--- a/src/hotspot/share/classfile/classLoaderData.cpp   Thu Mar 28 
19:43:59 2019 +0100
+++ b/src/hotspot/share/classfile/classLoaderData.cpp   Thu Mar 28 
16:11:59 2019 -0400
@@ -288,7 +288,7 @@
  // it is being defined, therefore _keep_alive is not volatile or atomic.
  void ClassLoaderData::inc_keep_alive() {
    if (is_unsafe_anonymous()) {
-    assert(_keep_alive >= 0, "Invalid keep alive increment count");
+    assert(_keep_alive > 0, "Invalid keep alive increment count");
      _keep_alive++;
    }
  }


Test:
   hotspot_runtime on Linux x86 fastdebug
   Sumbit tests.


Thanks,

-Zhengyu