8359105: RISC-V: No need for acquire fence in safepoint poll during JNI calls

Backport-of: 1a01839f8c0522a90710e101cce6ecc479a77529

Author: DingliZhang

src/hotspot/cpu/riscv/c1_LIRAssembler_riscv.cpp

@@ -401,7 +401,7 @@ void LIR_Assembler::return_op(LIR_Opr result, C1SafepointPollStub* code_stub) {
 
   code_stub->set_safepoint_offset(__ offset());
   __ relocate(relocInfo::poll_return_type);
-  __ safepoint_poll(*code_stub->entry(), true /* at_return */, false /* acquire */, true /* in_nmethod */);
+  __ safepoint_poll(*code_stub->entry(), true /* at_return */, true /* in_nmethod */);
   __ ret();
 }
 

src/hotspot/cpu/riscv/downcallLinker_riscv.cpp

@@ -287,7 +287,7 @@ void DowncallLinker::StubGenerator::generate() {
       __ membar(MacroAssembler::AnyAny);
     }
 
-    __ safepoint_poll(L_safepoint_poll_slow_path, true /* at_return */, true /* acquire */, false /* in_nmethod */);
+    __ safepoint_poll(L_safepoint_poll_slow_path, true /* at_return */, false /* in_nmethod */);
     __ lwu(t0, Address(xthread, JavaThread::suspend_flags_offset()));
     __ bnez(t0, L_safepoint_poll_slow_path);
 

src/hotspot/cpu/riscv/interp_masm_riscv.cpp

@@ -645,7 +645,7 @@ void InterpreterMacroAssembler::remove_activation(TosState state,
   // the stack, will call InterpreterRuntime::at_unwind.
   Label slow_path;
   Label fast_path;
-  safepoint_poll(slow_path, true /* at_return */, false /* acquire */, false /* in_nmethod */);
+  safepoint_poll(slow_path, true /* at_return */, false /* in_nmethod */);
   j(fast_path);
 
   bind(slow_path);

src/hotspot/cpu/riscv/macroAssembler_riscv.cpp

@@ -3773,11 +3773,8 @@ void MacroAssembler::check_klass_subtype(Register sub_klass,
   bind(L_failure);
 }
 
-void MacroAssembler::safepoint_poll(Label& slow_path, bool at_return, bool acquire, bool in_nmethod, Register tmp_reg) {
+void MacroAssembler::safepoint_poll(Label& slow_path, bool at_return, bool in_nmethod, Register tmp_reg) {
   ld(tmp_reg, Address(xthread, JavaThread::polling_word_offset()));
-  if (acquire) {
-    membar(MacroAssembler::LoadLoad | MacroAssembler::LoadStore);
-  }
   if (at_return) {
     bgtu(in_nmethod ? sp : fp, tmp_reg, slow_path, /* is_far */ true);
   } else {

src/hotspot/cpu/riscv/macroAssembler_riscv.hpp

@@ -44,7 +44,7 @@ class MacroAssembler: public Assembler {
 
   MacroAssembler(CodeBuffer* code) : Assembler(code) {}
 
-  void safepoint_poll(Label& slow_path, bool at_return, bool acquire, bool in_nmethod, Register tmp_reg = t0);
+  void safepoint_poll(Label& slow_path, bool at_return, bool in_nmethod, Register tmp_reg = t0);
 
   // Alignment
   int align(int modulus, int extra_offset = 0);

src/hotspot/cpu/riscv/riscv.ad

@@ -1493,7 +1493,7 @@ void MachEpilogNode::emit(C2_MacroAssembler *masm, PhaseRegAlloc *ra_) const {
       code_stub = &stub->entry();
     }
     __ relocate(relocInfo::poll_return_type);
-    __ safepoint_poll(*code_stub, true /* at_return */, false /* acquire */, true /* in_nmethod */);
+    __ safepoint_poll(*code_stub, true /* at_return */, true /* in_nmethod */);
   }
 }
 

src/hotspot/cpu/riscv/sharedRuntime_riscv.cpp

@@ -1777,15 +1777,7 @@ nmethod* SharedRuntime::generate_native_wrapper(MacroAssembler* masm,
 
   // check for safepoint operation in progress and/or pending suspend requests
   {
-    // We need an acquire here to ensure that any subsequent load of the
-    // global SafepointSynchronize::_state flag is ordered after this load
-    // of the thread-local polling word. We don't want this poll to
-    // return false (i.e. not safepointing) and a later poll of the global
-    // SafepointSynchronize::_state spuriously to return true.
-    // This is to avoid a race when we're in a native->Java transition
-    // racing the code which wakes up from a safepoint.
-
-    __ safepoint_poll(safepoint_in_progress, true /* at_return */, true /* acquire */, false /* in_nmethod */);
+    __ safepoint_poll(safepoint_in_progress, true /* at_return */, false /* in_nmethod */);
     __ lwu(t0, Address(xthread, JavaThread::suspend_flags_offset()));
     __ bnez(t0, safepoint_in_progress);
     __ bind(safepoint_in_progress_done);

src/hotspot/cpu/riscv/templateInterpreterGenerator_riscv.cpp

@@ -1229,15 +1229,7 @@ address TemplateInterpreterGenerator::generate_native_entry(bool synchronized) {
   {
     Label L, Continue;
 
-    // We need an acquire here to ensure that any subsequent load of the
-    // global SafepointSynchronize::_state flag is ordered after this load
-    // of the thread-local polling word. We don't want this poll to
-    // return false (i.e. not safepointing) and a later poll of the global
-    // SafepointSynchronize::_state spuriously to return true.
-    //
-    // This is to avoid a race when we're in a native->Java transition
-    // racing the code which wakes up from a safepoint.
-    __ safepoint_poll(L, true /* at_return */, true /* acquire */, false /* in_nmethod */);
+    __ safepoint_poll(L, true /* at_return */, false /* in_nmethod */);
     __ lwu(t1, Address(xthread, JavaThread::suspend_flags_offset()));
     __ beqz(t1, Continue);
     __ bind(L);
@@ -1388,7 +1380,7 @@ address TemplateInterpreterGenerator::generate_native_entry(bool synchronized) {
 
   Label slow_path;
   Label fast_path;
-  __ safepoint_poll(slow_path, true /* at_return */, false /* acquire */, false /* in_nmethod */);
+  __ safepoint_poll(slow_path, true /* at_return */, false /* in_nmethod */);
   __ j(fast_path);
 
   __ bind(slow_path);