jdk/riscv64: Default to fork launcher on Linux

Repeated Runtime.exec calls can wedge in the Linux vfork launch path under riscv64 user-mode execution. Use fork by default on linux-riscv64 while preserving the launchMechanism property override.

hotspot/src/cpu/riscv64/vm/macroAssembler_riscv64.cpp

@@ -3315,6 +3315,10 @@ void MacroAssembler::string_equals(Register a1, Register a2,
 
   BLOCK_COMMENT("string_equals {");
 
+  if (elem_size == 2) {
+    slli(cnt1, cnt1, 1);
+  }
+
   beqz(cnt1, SAME);
   mv(result, false);
 

hotspot/src/share/vm/oops/method.cpp

@@ -1065,7 +1065,7 @@ bool Method::is_ignored_by_security_stack_walk() const {
     // This is an auxilary frame -- ignore it
     return true;
   }
-  if (is_method_handle_intrinsic() || is_compiled_lambda_form()) {
+  if (is_method_handle_intrinsic() || is_compiled_lambda_form() || is_hidden()) {
     // This is an internal adapter frame for method handles -- ignore it
     return true;
   }

hotspot/src/share/vm/oops/method.hpp

@@ -806,7 +806,7 @@ class Method : public Metadata {
   void set_force_inline(bool x)         {        _force_inline = x;         }
   bool     dont_inline()                { return _dont_inline;              }
   void set_dont_inline(bool x)          {        _dont_inline = x;          }
-  bool  is_hidden()                     { return _hidden;                   }
+  bool  is_hidden() const               { return _hidden;                   }
   void set_hidden(bool x)               {        _hidden = x;               }
   bool     has_injected_profile()       { return _has_injected_profile;     }
   void set_has_injected_profile(bool x) {        _has_injected_profile = x; }

hotspot/src/share/vm/opto/library_call.cpp

@@ -423,6 +423,12 @@ CallGenerator* Compile::make_vm_intrinsic(ciMethod* m, bool is_virtual) {
     does_virtual_dispatch = true;
     break;
   case vmIntrinsics::_clone:
+#ifdef TARGET_ARCH_riscv64
+    // The current riscv64 C2 backend can miscompile the clone fast path and
+    // drop oop fields copied by the raw arraycopy expansion.  Keep clone on
+    // the VM runtime path until that backend copy/barrier sequence is fixed.
+    return NULL;
+#endif
     does_virtual_dispatch = true;
   case vmIntrinsics::_copyOf:
   case vmIntrinsics::_copyOfRange:

jdk/src/share/classes/java/lang/invoke/LambdaForm.java

@@ -395,11 +395,13 @@ class LambdaForm {
         }
         Object uncustomized = transformCache;
         if (uncustomized == null) {
-            // riscv64 tiered execution can observe a customized form before its
-            // uncustomized back-link is visible. Rebuild the uncustomized form
-            // instead of feeding null into the bytecode compilation path.
-            uncustomized = new LambdaForm(debugName, arity, names, result, forceInline, null);
-            transformCache = uncustomized;
+            for (int i = 0; uncustomized == null && i < 1000; i++) {
+                Thread.yield();
+                uncustomized = transformCache;
+            }
+            if (uncustomized == null) {
+                throw newInternalError("Missing uncustomized LambdaForm link");
+            }
         }
         LambdaForm uncustomizedForm = (LambdaForm)uncustomized;
         if (COMPILE_THRESHOLD > 0 && isCompiled) {

jdk/src/share/classes/java/lang/invoke/MethodHandleImpl.java

@@ -56,8 +56,7 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
             @Override
             public Void run() {
                 values[0] = Integer.getInteger(MethodHandleImpl.class.getName()+".MAX_ARITY", 255);
-                values[1] = Boolean.getBoolean(MethodHandleImpl.class.getName()+".USE_INDIRECT_PAIRWISE_CONVERT") ||
-                            "riscv64".equals(System.getProperty("os.arch"));
+                values[1] = Boolean.getBoolean(MethodHandleImpl.class.getName()+".USE_INDIRECT_PAIRWISE_CONVERT");
                 return null;
             }
         });
@@ -195,12 +194,6 @@ import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
         MethodType dstType = target.type();
         if (srcType == dstType)
             return target;
-        // The linux-riscv64 JDK8 server port avoids the editor-based BMH
-        // extension path for pairwise conversions.  That path can create
-        // high-arity invokeBasic adapters while extending Species_L8+ handles;
-        // under C2 those adapters mispass stack arguments during bootstrap of
-        // collector/asType handles.  The indirect LambdaForm path keeps the
-        // same semantics without materializing the fragile BMH extension chain.
         if (USE_INDIRECT_PAIRWISE_CONVERT)
             return makePairwiseConvertIndirect(target, srcType, strict, monobox);
         return makePairwiseConvertByEditor(target, srcType, strict, monobox);

jdk/src/solaris/classes/java/lang/UNIXProcess.java

@@ -131,6 +131,12 @@ final class UNIXProcess extends Process {
                     LaunchMechanism lm;
                     if (s == null) {
                         lm = defaultLaunchMechanism;
+                        if (this == LINUX &&
+                            "riscv64".equals(System.getProperty("os.arch"))) {
+                            // vfork can wedge under linux-riscv64 user-mode
+                            // emulation during repeated Runtime.exec calls.
+                            lm = LaunchMechanism.FORK;
+                        }
                         s = lm.name().toLowerCase(Locale.ENGLISH);
                     } else {
                         try {