jdk8-mips64-public/hotspot: src/share/vm/runtime/biasedLocking.cpp@fd44df5e3bc3 (annotated)

src/share/vm/runtime/biasedLocking.cpp@fd44df5e3bc3 (annotated)

src/share/vm/runtime/biasedLocking.cpp

Wed, 14 Oct 2020 17:44:48 +0800

author: aoqi
date: Wed, 14 Oct 2020 17:44:48 +0800
changeset 9931: fd44df5e3bc3
parent 6876: 710a3c8b516e
parent 9895: c439931136f1
permissions: -rw-r--r--

Merge

 /*
  * Copyright (c) 2005, 2014, 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 "precompiled.hpp"
 #include "oops/klass.inline.hpp"
 #include "oops/markOop.hpp"
 #include "runtime/basicLock.hpp"
 #include "runtime/biasedLocking.hpp"
 #include "runtime/task.hpp"
 #include "runtime/vframe.hpp"
 #include "runtime/vmThread.hpp"
 #include "runtime/vm_operations.hpp"
 #include "jfr/support/jfrThreadId.hpp"
 #include "jfr/jfrEvents.hpp"
 static bool _biased_locking_enabled = false;
 BiasedLockingCounters BiasedLocking::_counters;
 static GrowableArray<Handle>*  _preserved_oop_stack  = NULL;
 static GrowableArray<markOop>* _preserved_mark_stack = NULL;
 static void enable_biased_locking(Klass* k) {
   k->set_prototype_header(markOopDesc::biased_locking_prototype());
 }
 class VM_EnableBiasedLocking: public VM_Operation {
  private:
   bool _is_cheap_allocated;
  public:
   VM_EnableBiasedLocking(bool is_cheap_allocated) { _is_cheap_allocated = is_cheap_allocated; }
   VMOp_Type type() const          { return VMOp_EnableBiasedLocking; }
   Mode evaluation_mode() const    { return _is_cheap_allocated ? _async_safepoint : _safepoint; }
   bool is_cheap_allocated() const { return _is_cheap_allocated; }
   void doit() {
     // Iterate the system dictionary enabling biased locking for all
     // currently loaded classes
     SystemDictionary::classes_do(enable_biased_locking);
     // Indicate that future instances should enable it as well
     _biased_locking_enabled = true;
     if (TraceBiasedLocking) {
       tty->print_cr("Biased locking enabled");
     }
   }
   bool allow_nested_vm_operations() const        { return false; }
 };
 // One-shot PeriodicTask subclass for enabling biased locking
 class EnableBiasedLockingTask : public PeriodicTask {
  public:
   EnableBiasedLockingTask(size_t interval_time) : PeriodicTask(interval_time) {}
   virtual void task() {
     // Use async VM operation to avoid blocking the Watcher thread.
     // VM Thread will free C heap storage.
     VM_EnableBiasedLocking *op = new VM_EnableBiasedLocking(true);
     VMThread::execute(op);
     // Reclaim our storage and disenroll ourself
     delete this;
   }
 };
 void BiasedLocking::init() {
   // If biased locking is enabled, schedule a task to fire a few
   // seconds into the run which turns on biased locking for all
   // currently loaded classes as well as future ones. This is a
   // workaround for startup time regressions due to a large number of
   // safepoints being taken during VM startup for bias revocation.
   // Ideally we would have a lower cost for individual bias revocation
   // and not need a mechanism like this.
   if (UseBiasedLocking) {
     if (BiasedLockingStartupDelay > 0) {
       EnableBiasedLockingTask* task = new EnableBiasedLockingTask(BiasedLockingStartupDelay);
       task->enroll();
     } else {
       VM_EnableBiasedLocking op(false);
       VMThread::execute(&op);
     }
   }
 }
 bool BiasedLocking::enabled() {
   return _biased_locking_enabled;
 }
 // Returns MonitorInfos for all objects locked on this thread in youngest to oldest order
 static GrowableArray<MonitorInfo*>* get_or_compute_monitor_info(JavaThread* thread) {
   GrowableArray<MonitorInfo*>* info = thread->cached_monitor_info();
   if (info != NULL) {
     return info;
   }
   info = new GrowableArray<MonitorInfo*>();
   // It's possible for the thread to not have any Java frames on it,
   // i.e., if it's the main thread and it's already returned from main()
   if (thread->has_last_Java_frame()) {
     RegisterMap rm(thread);
     for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) {
       GrowableArray<MonitorInfo*> *monitors = vf->monitors();
       if (monitors != NULL) {
         int len = monitors->length();
         // Walk monitors youngest to oldest
         for (int i = len - 1; i >= 0; i--) {
           MonitorInfo* mon_info = monitors->at(i);
           if (mon_info->eliminated()) continue;
           oop owner = mon_info->owner();
           if (owner != NULL) {
             info->append(mon_info);
           }
         }
       }
     }
   }
   thread->set_cached_monitor_info(info);
   return info;
 }
 // After the call, *biased_locker will be set to obj->mark()->biased_locker() if biased_locker != NULL,
 // AND it is a living thread. Otherwise it will not be updated, (i.e. the caller is responsible for initialization).
 static BiasedLocking::Condition revoke_bias(oop obj, bool allow_rebias, bool is_bulk, JavaThread* requesting_thread, JavaThread** biased_locker) {
   markOop mark = obj->mark();
   if (!mark->has_bias_pattern()) {
     if (TraceBiasedLocking) {
       ResourceMark rm;
       tty->print_cr("  (Skipping revocation of object of type %s because it's no longer biased)",
                     obj->klass()->external_name());
     }
     return BiasedLocking::NOT_BIASED;
   }
   uint age = mark->age();
   markOop   biased_prototype = markOopDesc::biased_locking_prototype()->set_age(age);
   markOop unbiased_prototype = markOopDesc::prototype()->set_age(age);
   if (TraceBiasedLocking && (Verbose || !is_bulk)) {
     ResourceMark rm;
     tty->print_cr("Revoking bias of object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s , prototype header " INTPTR_FORMAT " , allow rebias %d , requesting thread " INTPTR_FORMAT,
                   p2i((void *)obj), (intptr_t) mark, obj->klass()->external_name(), (intptr_t) obj->klass()->prototype_header(), (allow_rebias ? 1 : 0), (intptr_t) requesting_thread);
   }
   JavaThread* biased_thread = mark->biased_locker();
   if (biased_thread == NULL) {
     // Object is anonymously biased. We can get here if, for
     // example, we revoke the bias due to an identity hash code
     // being computed for an object.
     if (!allow_rebias) {
       obj->set_mark(unbiased_prototype);
     }
     if (TraceBiasedLocking && (Verbose || !is_bulk)) {
       tty->print_cr("  Revoked bias of anonymously-biased object");
     }
     return BiasedLocking::BIAS_REVOKED;
   }
   // Handle case where the thread toward which the object was biased has exited
   bool thread_is_alive = false;
   if (requesting_thread == biased_thread) {
     thread_is_alive = true;
   } else {
     for (JavaThread* cur_thread = Threads::first(); cur_thread != NULL; cur_thread = cur_thread->next()) {
       if (cur_thread == biased_thread) {
         thread_is_alive = true;
         break;
       }
     }
   }
   if (!thread_is_alive) {
     if (allow_rebias) {
       obj->set_mark(biased_prototype);
     } else {
       obj->set_mark(unbiased_prototype);
     }
     if (TraceBiasedLocking && (Verbose || !is_bulk)) {
       tty->print_cr("  Revoked bias of object biased toward dead thread");
     }
     return BiasedLocking::BIAS_REVOKED;
   }
   // Thread owning bias is alive.
   // Check to see whether it currently owns the lock and, if so,
   // write down the needed displaced headers to the thread's stack.
   // Otherwise, restore the object's header either to the unlocked
   // or unbiased state.
   GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(biased_thread);
   BasicLock* highest_lock = NULL;
   for (int i = 0; i < cached_monitor_info->length(); i++) {
     MonitorInfo* mon_info = cached_monitor_info->at(i);
     if (mon_info->owner() == obj) {
       if (TraceBiasedLocking && Verbose) {
         tty->print_cr("   mon_info->owner (" PTR_FORMAT ") == obj (" PTR_FORMAT ")",
                       p2i((void *) mon_info->owner()),
                       p2i((void *) obj));
       }
       // Assume recursive case and fix up highest lock later
       markOop mark = markOopDesc::encode((BasicLock*) NULL);
       highest_lock = mon_info->lock();
       highest_lock->set_displaced_header(mark);
     } else {
       if (TraceBiasedLocking && Verbose) {
         tty->print_cr("   mon_info->owner (" PTR_FORMAT ") != obj (" PTR_FORMAT ")",
                       p2i((void *) mon_info->owner()),
                       p2i((void *) obj));
       }
     }
   }
   if (highest_lock != NULL) {
     // Fix up highest lock to contain displaced header and point
     // object at it
     highest_lock->set_displaced_header(unbiased_prototype);
     // Reset object header to point to displaced mark.
     // Must release storing the lock address for platforms without TSO
     // ordering (e.g. ppc).
     obj->release_set_mark(markOopDesc::encode(highest_lock));
     assert(!obj->mark()->has_bias_pattern(), "illegal mark state: stack lock used bias bit");
     if (TraceBiasedLocking && (Verbose || !is_bulk)) {
       tty->print_cr("  Revoked bias of currently-locked object");
     }
   } else {
     if (TraceBiasedLocking && (Verbose || !is_bulk)) {
       tty->print_cr("  Revoked bias of currently-unlocked object");
     }
     if (allow_rebias) {
       obj->set_mark(biased_prototype);
     } else {
       // Store the unlocked value into the object's header.
       obj->set_mark(unbiased_prototype);
     }
   }
 #if INCLUDE_JFR
   // If requested, return information on which thread held the bias
   if (biased_locker != NULL) {
     *biased_locker = biased_thread;
   }
 #endif // INCLUDE_JFR
   return BiasedLocking::BIAS_REVOKED;
 }
 enum HeuristicsResult {
   HR_NOT_BIASED    = 1,
   HR_SINGLE_REVOKE = 2,
   HR_BULK_REBIAS   = 3,
   HR_BULK_REVOKE   = 4
 };
 static HeuristicsResult update_heuristics(oop o, bool allow_rebias) {
   markOop mark = o->mark();
   if (!mark->has_bias_pattern()) {
     return HR_NOT_BIASED;
   }
   // Heuristics to attempt to throttle the number of revocations.
   // Stages:
   // 1. Revoke the biases of all objects in the heap of this type,
   //    but allow rebiasing of those objects if unlocked.
   // 2. Revoke the biases of all objects in the heap of this type
   //    and don't allow rebiasing of these objects. Disable
   //    allocation of objects of that type with the bias bit set.
   Klass* k = o->klass();
   jlong cur_time = os::javaTimeMillis();
   jlong last_bulk_revocation_time = k->last_biased_lock_bulk_revocation_time();
   int revocation_count = k->biased_lock_revocation_count();
   if ((revocation_count >= BiasedLockingBulkRebiasThreshold) &&
       (revocation_count <  BiasedLockingBulkRevokeThreshold) &&
       (last_bulk_revocation_time != 0) &&
       (cur_time - last_bulk_revocation_time >= BiasedLockingDecayTime)) {
     // This is the first revocation we've seen in a while of an
     // object of this type since the last time we performed a bulk
     // rebiasing operation. The application is allocating objects in
     // bulk which are biased toward a thread and then handing them
     // off to another thread. We can cope with this allocation
     // pattern via the bulk rebiasing mechanism so we reset the
     // klass's revocation count rather than allow it to increase
     // monotonically. If we see the need to perform another bulk
     // rebias operation later, we will, and if subsequently we see
     // many more revocation operations in a short period of time we
     // will completely disable biasing for this type.
     k->set_biased_lock_revocation_count(0);
     revocation_count = 0;
   }
   // Make revocation count saturate just beyond BiasedLockingBulkRevokeThreshold
   if (revocation_count <= BiasedLockingBulkRevokeThreshold) {
     revocation_count = k->atomic_incr_biased_lock_revocation_count();
   }
   if (revocation_count == BiasedLockingBulkRevokeThreshold) {
     return HR_BULK_REVOKE;
   }
   if (revocation_count == BiasedLockingBulkRebiasThreshold) {
     return HR_BULK_REBIAS;
   }
   return HR_SINGLE_REVOKE;
 }
 static BiasedLocking::Condition bulk_revoke_or_rebias_at_safepoint(oop o,
                                                                    bool bulk_rebias,
                                                                    bool attempt_rebias_of_object,
                                                                    JavaThread* requesting_thread) {
   assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint");
   if (TraceBiasedLocking) {
     tty->print_cr("* Beginning bulk revocation (kind == %s) because of object "
                   INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s",
                   (bulk_rebias ? "rebias" : "revoke"),
                   p2i((void *) o), (intptr_t) o->mark(), o->klass()->external_name());
   }
   jlong cur_time = os::javaTimeMillis();
   o->klass()->set_last_biased_lock_bulk_revocation_time(cur_time);
   Klass* k_o = o->klass();
   Klass* klass = k_o;
   if (bulk_rebias) {
     // Use the epoch in the klass of the object to implicitly revoke
     // all biases of objects of this data type and force them to be
     // reacquired. However, we also need to walk the stacks of all
     // threads and update the headers of lightweight locked objects
     // with biases to have the current epoch.
     // If the prototype header doesn't have the bias pattern, don't
     // try to update the epoch -- assume another VM operation came in
     // and reset the header to the unbiased state, which will
     // implicitly cause all existing biases to be revoked
     if (klass->prototype_header()->has_bias_pattern()) {
       int prev_epoch = klass->prototype_header()->bias_epoch();
       klass->set_prototype_header(klass->prototype_header()->incr_bias_epoch());
       int cur_epoch = klass->prototype_header()->bias_epoch();
       // Now walk all threads' stacks and adjust epochs of any biased
       // and locked objects of this data type we encounter
       for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
         GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr);
         for (int i = 0; i < cached_monitor_info->length(); i++) {
           MonitorInfo* mon_info = cached_monitor_info->at(i);
           oop owner = mon_info->owner();
           markOop mark = owner->mark();
           if ((owner->klass() == k_o) && mark->has_bias_pattern()) {
             // We might have encountered this object already in the case of recursive locking
             assert(mark->bias_epoch() == prev_epoch || mark->bias_epoch() == cur_epoch, "error in bias epoch adjustment");
             owner->set_mark(mark->set_bias_epoch(cur_epoch));
           }
         }
       }
     }
     // At this point we're done. All we have to do is potentially
     // adjust the header of the given object to revoke its bias.
     revoke_bias(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread, NULL);
   } else {
     if (TraceBiasedLocking) {
       ResourceMark rm;
       tty->print_cr("* Disabling biased locking for type %s", klass->external_name());
     }
     // Disable biased locking for this data type. Not only will this
     // cause future instances to not be biased, but existing biased
     // instances will notice that this implicitly caused their biases
     // to be revoked.
     klass->set_prototype_header(markOopDesc::prototype());
     // Now walk all threads' stacks and forcibly revoke the biases of
     // any locked and biased objects of this data type we encounter.
     for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
       GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr);
       for (int i = 0; i < cached_monitor_info->length(); i++) {
         MonitorInfo* mon_info = cached_monitor_info->at(i);
         oop owner = mon_info->owner();
         markOop mark = owner->mark();
         if ((owner->klass() == k_o) && mark->has_bias_pattern()) {
           revoke_bias(owner, false, true, requesting_thread, NULL);
         }
       }
     }
     // Must force the bias of the passed object to be forcibly revoked
     // as well to ensure guarantees to callers
     revoke_bias(o, false, true, requesting_thread, NULL);
   }
   if (TraceBiasedLocking) {
     tty->print_cr("* Ending bulk revocation");
   }
   BiasedLocking::Condition status_code = BiasedLocking::BIAS_REVOKED;
   if (attempt_rebias_of_object &&
       o->mark()->has_bias_pattern() &&
       klass->prototype_header()->has_bias_pattern()) {
     markOop new_mark = markOopDesc::encode(requesting_thread, o->mark()->age(),
                                            klass->prototype_header()->bias_epoch());
     o->set_mark(new_mark);
     status_code = BiasedLocking::BIAS_REVOKED_AND_REBIASED;
     if (TraceBiasedLocking) {
       tty->print_cr("  Rebiased object toward thread " INTPTR_FORMAT, (intptr_t) requesting_thread);
     }
   }
   assert(!o->mark()->has_bias_pattern() ||
          (attempt_rebias_of_object && (o->mark()->biased_locker() == requesting_thread)),
          "bug in bulk bias revocation");
   return status_code;
 }
 static void clean_up_cached_monitor_info() {
   // Walk the thread list clearing out the cached monitors
   for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
     thr->set_cached_monitor_info(NULL);
   }
 }
 class VM_RevokeBias : public VM_Operation {
 protected:
   Handle* _obj;
   GrowableArray<Handle>* _objs;
   JavaThread* _requesting_thread;
   BiasedLocking::Condition _status_code;
   traceid _biased_locker_id;
 public:
   VM_RevokeBias(Handle* obj, JavaThread* requesting_thread)
     : _obj(obj)
     , _objs(NULL)
     , _requesting_thread(requesting_thread)
     , _status_code(BiasedLocking::NOT_BIASED)
     , _biased_locker_id(0) {}
   VM_RevokeBias(GrowableArray<Handle>* objs, JavaThread* requesting_thread)
     : _obj(NULL)
     , _objs(objs)
     , _requesting_thread(requesting_thread)
     , _status_code(BiasedLocking::NOT_BIASED)
     , _biased_locker_id(0) {}
   virtual VMOp_Type type() const { return VMOp_RevokeBias; }
   virtual bool doit_prologue() {
     // Verify that there is actual work to do since the callers just
     // give us locked object(s). If we don't find any biased objects
     // there is nothing to do and we avoid a safepoint.
     if (_obj != NULL) {
       markOop mark = (*_obj)()->mark();
       if (mark->has_bias_pattern()) {
         return true;
       }
     } else {
       for ( int i = 0 ; i < _objs->length(); i++ ) {
         markOop mark = (_objs->at(i))()->mark();
         if (mark->has_bias_pattern()) {
           return true;
         }
       }
     }
     return false;
   }
   virtual void doit() {
     if (_obj != NULL) {
       if (TraceBiasedLocking) {
         tty->print_cr("Revoking bias with potentially per-thread safepoint:");
       }
       JavaThread* biased_locker = NULL;
       _status_code = revoke_bias((*_obj)(), false, false, _requesting_thread, &biased_locker);
 #if INCLUDE_JFR
       if (biased_locker != NULL) {
         _biased_locker_id = JFR_THREAD_ID(biased_locker);
       }
 #endif // INCLUDE_JFR
       clean_up_cached_monitor_info();
       return;
     } else {
       if (TraceBiasedLocking) {
         tty->print_cr("Revoking bias with global safepoint:");
       }
       BiasedLocking::revoke_at_safepoint(_objs);
     }
   }
   BiasedLocking::Condition status_code() const {
     return _status_code;
   }
   traceid biased_locker() const {
     return _biased_locker_id;
   }
 };
 class VM_BulkRevokeBias : public VM_RevokeBias {
 private:
   bool _bulk_rebias;
   bool _attempt_rebias_of_object;
 public:
   VM_BulkRevokeBias(Handle* obj, JavaThread* requesting_thread,
                     bool bulk_rebias,
                     bool attempt_rebias_of_object)
     : VM_RevokeBias(obj, requesting_thread)
     , _bulk_rebias(bulk_rebias)
     , _attempt_rebias_of_object(attempt_rebias_of_object) {}
   virtual VMOp_Type type() const { return VMOp_BulkRevokeBias; }
   virtual bool doit_prologue()   { return true; }
   virtual void doit() {
     _status_code = bulk_revoke_or_rebias_at_safepoint((*_obj)(), _bulk_rebias, _attempt_rebias_of_object, _requesting_thread);
     clean_up_cached_monitor_info();
   }
 };
 BiasedLocking::Condition BiasedLocking::revoke_and_rebias(Handle obj, bool attempt_rebias, TRAPS) {
   assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint");
   // We can revoke the biases of anonymously-biased objects
   // efficiently enough that we should not cause these revocations to
   // update the heuristics because doing so may cause unwanted bulk
   // revocations (which are expensive) to occur.
   markOop mark = obj->mark();
   if (mark->is_biased_anonymously() && !attempt_rebias) {
     // We are probably trying to revoke the bias of this object due to
     // an identity hash code computation. Try to revoke the bias
     // without a safepoint. This is possible if we can successfully
     // compare-and-exchange an unbiased header into the mark word of
     // the object, meaning that no other thread has raced to acquire
     // the bias of the object.
     markOop biased_value       = mark;
     markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age());
     markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark);
     if (res_mark == biased_value) {
       return BIAS_REVOKED;
     }
   } else if (mark->has_bias_pattern()) {
     Klass* k = obj->klass();
     markOop prototype_header = k->prototype_header();
     if (!prototype_header->has_bias_pattern()) {
       // This object has a stale bias from before the bulk revocation
       // for this data type occurred. It's pointless to update the
       // heuristics at this point so simply update the header with a
       // CAS. If we fail this race, the object's bias has been revoked
       // by another thread so we simply return and let the caller deal
       // with it.
       markOop biased_value       = mark;
       markOop res_mark = (markOop) Atomic::cmpxchg_ptr(prototype_header, obj->mark_addr(), mark);
       assert(!(*(obj->mark_addr()))->has_bias_pattern(), "even if we raced, should still be revoked");
       return BIAS_REVOKED;
     } else if (prototype_header->bias_epoch() != mark->bias_epoch()) {
       // The epoch of this biasing has expired indicating that the
       // object is effectively unbiased. Depending on whether we need
       // to rebias or revoke the bias of this object we can do it
       // efficiently enough with a CAS that we shouldn't update the
       // heuristics. This is normally done in the assembly code but we
       // can reach this point due to various points in the runtime
       // needing to revoke biases.
       if (attempt_rebias) {
         assert(THREAD->is_Java_thread(), "");
         markOop biased_value       = mark;
         markOop rebiased_prototype = markOopDesc::encode((JavaThread*) THREAD, mark->age(), prototype_header->bias_epoch());
         markOop res_mark = (markOop) Atomic::cmpxchg_ptr(rebiased_prototype, obj->mark_addr(), mark);
         if (res_mark == biased_value) {
           return BIAS_REVOKED_AND_REBIASED;
         }
       } else {
         markOop biased_value       = mark;
         markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age());
         markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark);
         if (res_mark == biased_value) {
           return BIAS_REVOKED;
         }
       }
     }
   }
   HeuristicsResult heuristics = update_heuristics(obj(), attempt_rebias);
   if (heuristics == HR_NOT_BIASED) {
     return NOT_BIASED;
   } else if (heuristics == HR_SINGLE_REVOKE) {
     Klass *k = obj->klass();
     markOop prototype_header = k->prototype_header();
     if (mark->biased_locker() == THREAD &&
         prototype_header->bias_epoch() == mark->bias_epoch()) {
       // A thread is trying to revoke the bias of an object biased
       // toward it, again likely due to an identity hash code
       // computation. We can again avoid a safepoint in this case
       // since we are only going to walk our own stack. There are no
       // races with revocations occurring in other threads because we
       // reach no safepoints in the revocation path.
       // Also check the epoch because even if threads match, another thread
       // can come in with a CAS to steal the bias of an object that has a
       // stale epoch.
       ResourceMark rm;
       if (TraceBiasedLocking) {
         tty->print_cr("Revoking bias by walking my own stack:");
       }
       EventBiasedLockSelfRevocation event;
       BiasedLocking::Condition cond = revoke_bias(obj(), false, false, (JavaThread*) THREAD, NULL);
       ((JavaThread*) THREAD)->set_cached_monitor_info(NULL);
       assert(cond == BIAS_REVOKED, "why not?");
       if (event.should_commit()) {
         event.set_lockClass(k);
         event.commit();
       }
       return cond;
     } else {
       EventBiasedLockRevocation event;
       VM_RevokeBias revoke(&obj, (JavaThread*) THREAD);
       VMThread::execute(&revoke);
       if (event.should_commit() && (revoke.status_code() != NOT_BIASED)) {
         event.set_lockClass(k);
         // Subtract 1 to match the id of events committed inside the safepoint
         event.set_safepointId(SafepointSynchronize::safepoint_counter() - 1);
         event.set_previousOwner(revoke.biased_locker());
         event.commit();
       }
       return revoke.status_code();
     }
   }
   assert((heuristics == HR_BULK_REVOKE) ||
          (heuristics == HR_BULK_REBIAS), "?");
   EventBiasedLockClassRevocation event;
   VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*) THREAD,
                                 (heuristics == HR_BULK_REBIAS),
                                 attempt_rebias);
   VMThread::execute(&bulk_revoke);
   if (event.should_commit()) {
     event.set_revokedClass(obj->klass());
     event.set_disableBiasing((heuristics != HR_BULK_REBIAS));
     // Subtract 1 to match the id of events committed inside the safepoint
     event.set_safepointId(SafepointSynchronize::safepoint_counter() - 1);
     event.commit();
   }
   return bulk_revoke.status_code();
 }
 void BiasedLocking::revoke(GrowableArray<Handle>* objs) {
   assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint");
   if (objs->length() == 0) {
     return;
   }
   VM_RevokeBias revoke(objs, JavaThread::current());
   VMThread::execute(&revoke);
 }
 void BiasedLocking::revoke_at_safepoint(Handle h_obj) {
   assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint");
   oop obj = h_obj();
   HeuristicsResult heuristics = update_heuristics(obj, false);
   if (heuristics == HR_SINGLE_REVOKE) {
     revoke_bias(obj, false, false, NULL, NULL);
   } else if ((heuristics == HR_BULK_REBIAS) ||
              (heuristics == HR_BULK_REVOKE)) {
     bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL);
   }
   clean_up_cached_monitor_info();
 }
 void BiasedLocking::revoke_at_safepoint(GrowableArray<Handle>* objs) {
   assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint");
   int len = objs->length();
   for (int i = 0; i < len; i++) {
     oop obj = (objs->at(i))();
     HeuristicsResult heuristics = update_heuristics(obj, false);
     if (heuristics == HR_SINGLE_REVOKE) {
       revoke_bias(obj, false, false, NULL, NULL);
     } else if ((heuristics == HR_BULK_REBIAS) ||
                (heuristics == HR_BULK_REVOKE)) {
       bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL);
     }
   }
   clean_up_cached_monitor_info();
 }
 void BiasedLocking::preserve_marks() {
   if (!UseBiasedLocking)
     return;
   assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint");
   assert(_preserved_oop_stack  == NULL, "double initialization");
   assert(_preserved_mark_stack == NULL, "double initialization");
   // In order to reduce the number of mark words preserved during GC
   // due to the presence of biased locking, we reinitialize most mark
   // words to the class's prototype during GC -- even those which have
   // a currently valid bias owner. One important situation where we
   // must not clobber a bias is when a biased object is currently
   // locked. To handle this case we iterate over the currently-locked
   // monitors in a prepass and, if they are biased, preserve their
   // mark words here. This should be a relatively small set of objects
   // especially compared to the number of objects in the heap.
   _preserved_mark_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<markOop>(10, true);
   _preserved_oop_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<Handle>(10, true);
   ResourceMark rm;
   Thread* cur = Thread::current();
   for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
     if (thread->has_last_Java_frame()) {
       RegisterMap rm(thread);
       for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) {
         GrowableArray<MonitorInfo*> *monitors = vf->monitors();
         if (monitors != NULL) {
           int len = monitors->length();
           // Walk monitors youngest to oldest
           for (int i = len - 1; i >= 0; i--) {
             MonitorInfo* mon_info = monitors->at(i);
             if (mon_info->owner_is_scalar_replaced()) continue;
             oop owner = mon_info->owner();
             if (owner != NULL) {
               markOop mark = owner->mark();
               if (mark->has_bias_pattern()) {
                 _preserved_oop_stack->push(Handle(cur, owner));
                 _preserved_mark_stack->push(mark);
               }
             }
           }
         }
       }
     }
   }
 }
 void BiasedLocking::restore_marks() {
   if (!UseBiasedLocking)
     return;
   assert(_preserved_oop_stack  != NULL, "double free");
   assert(_preserved_mark_stack != NULL, "double free");
   int len = _preserved_oop_stack->length();
   for (int i = 0; i < len; i++) {
     Handle owner = _preserved_oop_stack->at(i);
     markOop mark = _preserved_mark_stack->at(i);
     owner->set_mark(mark);
   }
   delete _preserved_oop_stack;
   _preserved_oop_stack = NULL;
   delete _preserved_mark_stack;
   _preserved_mark_stack = NULL;
 }
 int* BiasedLocking::total_entry_count_addr()                   { return _counters.total_entry_count_addr(); }
 int* BiasedLocking::biased_lock_entry_count_addr()             { return _counters.biased_lock_entry_count_addr(); }
 int* BiasedLocking::anonymously_biased_lock_entry_count_addr() { return _counters.anonymously_biased_lock_entry_count_addr(); }
 int* BiasedLocking::rebiased_lock_entry_count_addr()           { return _counters.rebiased_lock_entry_count_addr(); }
 int* BiasedLocking::revoked_lock_entry_count_addr()            { return _counters.revoked_lock_entry_count_addr(); }
 int* BiasedLocking::fast_path_entry_count_addr()               { return _counters.fast_path_entry_count_addr(); }
 int* BiasedLocking::slow_path_entry_count_addr()               { return _counters.slow_path_entry_count_addr(); }
 // BiasedLockingCounters
 int BiasedLockingCounters::slow_path_entry_count() {
   if (_slow_path_entry_count != 0) {
     return _slow_path_entry_count;
   }
   int sum = _biased_lock_entry_count   + _anonymously_biased_lock_entry_count +
             _rebiased_lock_entry_count + _revoked_lock_entry_count +
             _fast_path_entry_count;
   return _total_entry_count - sum;
 }
 void BiasedLockingCounters::print_on(outputStream* st) {
   tty->print_cr("# total entries: %d", _total_entry_count);
   tty->print_cr("# biased lock entries: %d", _biased_lock_entry_count);
   tty->print_cr("# anonymously biased lock entries: %d", _anonymously_biased_lock_entry_count);
   tty->print_cr("# rebiased lock entries: %d", _rebiased_lock_entry_count);
   tty->print_cr("# revoked lock entries: %d", _revoked_lock_entry_count);
   tty->print_cr("# fast path lock entries: %d", _fast_path_entry_count);
   tty->print_cr("# slow path lock entries: %d", slow_path_entry_count());
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/runtime/biasedLocking.cpp@fd44df5e3bc3 (annotated)

src/share/vm/runtime/biasedLocking.cpp