8331411: Shenandoah: Reconsider spinning duration in ShenandoahLock

src/hotspot/share/gc/shenandoah/shenandoahLock.cpp

@@ -45,7 +45,7 @@ template<bool ALLOW_BLOCK>
 void ShenandoahLock::contended_lock_internal(JavaThread* java_thread) {
   assert(!ALLOW_BLOCK || java_thread != nullptr, "Must have a Java thread when allowing block.");
   // Spin this much on multi-processor, do not spin on multi-processor.
-  int ctr = os::is_MP() ? 0x1F : 0;
+  int ctr = os::is_MP() ? 0xFF : 0;
   // Apply TTAS to avoid more expensive CAS calls if the lock is still held by other thread.
   while (Atomic::load(&_state) == locked ||
          Atomic::cmpxchg(&_state, unlocked, locked) != unlocked) {

src/hotspot/share/gc/shenandoah/shenandoahLock.hpp

@@ -49,7 +49,7 @@ class ShenandoahLock  {
     assert(Atomic::load(&_owner) != Thread::current(), "reentrant locking attempt, would deadlock");
 
     if ((allow_block_for_safepoint && SafepointSynchronize::is_synchronizing()) ||
-        Atomic::cmpxchg(&_state, unlocked, locked) != unlocked) {
+        (Atomic::cmpxchg(&_state, unlocked, locked) != unlocked)) {
       // 1. Java thread, and there is a pending safepoint. Dive into contended locking
       //    immediately without trying anything else, and block.
       // 2. Fast lock fails, dive into contended lock handling.