6791815: Fix for 6471657 can cause deadlock on non-Solaris platforms when...

6791815: Fix for 6471657 can cause deadlock on non-Solaris platforms when initializing direct buffer support
Summary: Place the state transition inside the loop so that the VMThread could proceed for safepoint
Reviewed-by: dholmes, never, acorn

src/share/vm/prims/jni.cpp

@@ -2691,8 +2691,13 @@ static bool initializeDirectBufferSupport(JNIEnv* env, JavaThread* thread) {
 
     directBufferSupportInitializeEnded = 1;
   } else {
-    ThreadInVMfromNative tivn(thread); // set state as yield_all can call os:sleep
     while (!directBufferSupportInitializeEnded && !directBufferSupportInitializeFailed) {
+      // Set state as yield_all can call os:sleep. On Solaris, yield_all calls
+      // os::sleep which requires the VM state transition. On other platforms, it
+      // is not necessary. The following call to change the VM state is purposely
+      // put inside the loop to avoid potential deadlock when multiple threads
+      // try to call this method. See 6791815 for more details.
+      ThreadInVMfromNative tivn(thread);
       os::yield_all();
     }
   }