src/hotspot/share/runtime/basicLock.cpp - master - githubmirror/panama-vector

src/hotspot/share/runtime/basicLock.cpp
80 строк3 KB
Fredrik Bredberg
8365191: Cleanup after removing LockingMode related code
25 сен 2025, 11:15
25 сен 2025, 11:15847b107
/*
 * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "oops/oop.inline.hpp"
#include "runtime/basicLock.inline.hpp"
#include "runtime/objectMonitor.hpp"
#include "runtime/synchronizer.hpp"

void BasicLock::print_on(outputStream* st, oop owner) const {
  st->print("monitor");
  if (UseObjectMonitorTable) {
    ObjectMonitor* mon = object_monitor_cache();
    if (mon != nullptr) {
      mon->print_on(st);
    }
  }
}

void BasicLock::move_to(oop obj, BasicLock* dest) {
  // Check to see if we need to inflate the lock. This is only needed
  // if an object is locked using "this" lightweight monitor. In that
  // case, the displaced_header() is unlocked/neutral, because the
  // displaced_header() contains the header for the originally unlocked
  // object. However the lock could have already been inflated. But it
  // does not matter, this inflation will just be a no-op. For other cases,
  // the displaced header will be either 0x0 or 0x3, which are location
  // independent, therefore the BasicLock is free to move.
  //
  // During OSR we may need to relocate a BasicLock (which contains a
  // displaced word) from a location in an interpreter frame to a
  // new location in a compiled frame.  "this" refers to the source
  // BasicLock in the interpreter frame.  "dest" refers to the destination
  // BasicLock in the new compiled frame.  We *always* inflate in move_to()
  // when the object is locked using "this" lightweight monitor.
  //
  // The always-Inflate policy works properly, but it depends on the
  // inflated fast-path operations in fast_lock and fast_unlock to avoid
  // performance problems. See x86/macroAssembler_x86.cpp: fast_lock()
  // and fast_unlock() for examples.
  //
  // Note that there is a way to safely swing the object's markword from
  // one stack location to another.  This avoids inflation.  Obviously,
  // we need to ensure that both locations refer to the current thread's stack.
  // There are some subtle concurrency issues, however, and since the benefit is
  // small (given the support for inflated fast-path locking in the fast_lock, etc)
  // we'll leave that optimization for another time.

  if (UseObjectMonitorTable) {
    // Preserve the ObjectMonitor*, the cache is cleared when a box is reused
    // and only read while the lock is held, so no stale ObjectMonitor* is
    // encountered.
    dest->set_object_monitor_cache(object_monitor_cache());
  }
#ifdef ASSERT
  else {
    dest->set_bad_monitor_deopt();
  }
#endif
}