1 /*
  2  * Copyright (c) 2018, 2021, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #include "precompiled.hpp"
 26 #include "code/codeCache.hpp"
 27 #include "code/nmethod.hpp"
 28 #include "gc/shared/barrierSet.hpp"
 29 #include "gc/shared/barrierSetNMethod.hpp"
 30 #include "logging/log.hpp"

 31 #include "runtime/thread.hpp"
 32 #include "runtime/threadWXSetters.inline.hpp"
 33 #include "utilities/debug.hpp"
 34 








 35 int BarrierSetNMethod::disarmed_value() const {
 36   return *disarmed_value_address();
 37 }
 38 
 39 bool BarrierSetNMethod::supports_entry_barrier(nmethod* nm) {
 40   if (nm->method()->is_method_handle_intrinsic()) {
 41     return false;
 42   }
 43 




 44   if (!nm->is_native_method() && !nm->is_compiled_by_c2() && !nm->is_compiled_by_c1()) {
 45     return false;
 46   }
 47 
 48   return true;
 49 }
 50 







































 51 int BarrierSetNMethod::nmethod_stub_entry_barrier(address* return_address_ptr) {
 52   // Enable WXWrite: the function is called directly from nmethod_entry_barrier
 53   // stub.
 54   MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXWrite, Thread::current()));
 55 
 56   address return_address = *return_address_ptr;
 57   CodeBlob* cb = CodeCache::find_blob(return_address);
 58   assert(cb != NULL, "invariant");
 59 
 60   nmethod* nm = cb->as_nmethod();
 61   BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
 62 
 63   if (!bs_nm->is_armed(nm)) {
 64     return 0;
 65   }
 66 
 67   assert(!nm->is_osr_method(), "Should not reach here");
 68   // Called upon first entry after being armed
 69   bool may_enter = bs_nm->nmethod_entry_barrier(nm);
 70 
 71   // Diagnostic option to force deoptimization 1 in 3 times. It is otherwise
 72   // a very rare event.
 73   if (DeoptimizeNMethodBarriersALot) {
 74     static volatile uint32_t counter=0;
 75     if (Atomic::add(&counter, 1u) % 3 == 0) {
 76       may_enter = false;
 77     }
 78   }
 79 
 80   if (!may_enter) {
 81     log_trace(nmethod, barrier)("Deoptimizing nmethod: " PTR_FORMAT, p2i(nm));
 82     bs_nm->deoptimize(nm, return_address_ptr);
 83   }
 84   return may_enter ? 0 : 1;
 85 }
 86 
 87 bool BarrierSetNMethod::nmethod_osr_entry_barrier(nmethod* nm) {
 88   // This check depends on the invariant that all nmethods that are deoptimized / made not entrant
 89   // are NOT disarmed.
 90   // This invariant is important because a method can be deoptimized after the method have been
 91   // resolved / looked up by OSR by another thread. By not deoptimizing them we guarantee that
 92   // a deoptimized method will always hit the barrier and come to the same conclusion - deoptimize
 93   if (!is_armed(nm)) {
 94     return true;
 95   }
 96 
 97   assert(nm->is_osr_method(), "Should not reach here");
 98   log_trace(nmethod, barrier)("Running osr nmethod entry barrier: " PTR_FORMAT, p2i(nm));
 99   return nmethod_entry_barrier(nm);
100 }
--- EOF ---