openjdkjvmti/deopt_manager.cc

/* Copyright (C) 2017 The Android Open Source Project
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This file implements interfaces from the file jvmti.h. This implementation
 * is licensed under the same terms as the file jvmti.h.  The
 * copyright and license information for the file jvmti.h follows.
 *
 * Copyright (c) 2003, 2011, 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.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * version 2 for more details (a copy is included in the LICENSE file that
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#include <functional>
#include <iosfwd>
#include <mutex>

#include "deopt_manager.h"

#include "art_jvmti.h"
#include "art_method-inl.h"
#include "base/enums.h"
#include "base/mutex-inl.h"
#include "dex/dex_file_annotations.h"
#include "dex/modifiers.h"
#include "events-inl.h"
#include "gc/collector_type.h"
#include "gc/heap.h"
#include "gc/scoped_gc_critical_section.h"
#include "instrumentation.h"
#include "jit/jit.h"
#include "jni/jni_internal.h"
#include "mirror/class-inl.h"
#include "mirror/object_array-inl.h"
#include "nativehelper/scoped_local_ref.h"
#include "read_barrier_config.h"
#include "runtime_callbacks.h"
#include "scoped_thread_state_change-inl.h"
#include "scoped_thread_state_change.h"
#include "thread-current-inl.h"
#include "thread_list.h"
#include "ti_phase.h"

namespace openjdkjvmti {

// TODO We should make this much more selective in the future so we only return true when we
// actually care about the method at this time (ie active frames had locals changed). For now we
// just assume that if anything has changed any frame's locals we care about all methods. If nothing
// has we only care about methods with active breakpoints on them. In the future we should probably
// rewrite all of this to instead do this at the ShadowFrame or thread granularity.
bool JvmtiMethodInspectionCallback::IsMethodBeingInspected(art::ArtMethod* method) {
  // In non-java-debuggable runtimes the breakpoint check would miss if we have breakpoints on
  // methods that are inlined. Since these features are best effort in non-java-debuggable
  // runtimes it is OK to be less precise. For debuggable runtimes, inlining is disabled.
  return manager_->HaveLocalsChanged() || manager_->MethodHasBreakpoints(method);
}

DeoptManager::DeoptManager()
  : deoptimization_status_lock_("JVMTI_DeoptimizationStatusLock",
                                static_cast<art::LockLevel>(
                                    art::LockLevel::kClassLinkerClassesLock + 1)),
    deoptimization_condition_("JVMTI_DeoptimizationCondition", deoptimization_status_lock_),
    performing_deoptimization_(false),
    global_deopt_count_(0),
    deopter_count_(0),
    breakpoint_status_lock_("JVMTI_BreakpointStatusLock",
                            static_cast<art::LockLevel>(art::LockLevel::kAbortLock + 1)),
    inspection_callback_(this),
    set_local_variable_called_(false) { }

void DeoptManager::Setup() {
  art::ScopedThreadStateChange stsc(art::Thread::Current(),
                                    art::ThreadState::kWaitingForDebuggerToAttach);
  art::ScopedSuspendAll ssa("Add method Inspection Callback");
  art::RuntimeCallbacks* callbacks = art::Runtime::Current()->GetRuntimeCallbacks();
  callbacks->AddMethodInspectionCallback(&inspection_callback_);
}

void DeoptManager::Shutdown() {
  art::ScopedThreadStateChange stsc(art::Thread::Current(),
                                    art::ThreadState::kWaitingForDebuggerToAttach);
  art::ScopedSuspendAll ssa("remove method Inspection Callback");
  art::RuntimeCallbacks* callbacks = art::Runtime::Current()->GetRuntimeCallbacks();
  callbacks->RemoveMethodInspectionCallback(&inspection_callback_);
}

void DeoptManager::DumpDeoptInfo(art::Thread* self, std::ostream& stream) {
  art::ScopedObjectAccess soa(self);
  art::MutexLock mutll(self, *art::Locks::thread_list_lock_);
  art::MutexLock mudsl(self, deoptimization_status_lock_);
  art::MutexLock mubsl(self, breakpoint_status_lock_);
  stream << "Deoptimizer count: " << deopter_count_ << "\n";
  stream << "Global deopt count: " << global_deopt_count_ << "\n";
  stream << "Can perform OSR: " << !set_local_variable_called_.load() << "\n";
  for (const auto& [bp, loc] : this->breakpoint_status_) {
    stream << "Breakpoint: " << bp->PrettyMethod() << " @ 0x" << std::hex << loc << "\n";
  }
  struct DumpThreadDeoptCount : public art::Closure {
   public:
    DumpThreadDeoptCount(std::ostream& stream, std::mutex& mu)
        : cnt_(0), stream_(stream), mu_(mu) {}
    void Run(art::Thread* self) override {
      {
        std::lock_guard<std::mutex> lg(mu_);
        std::string name;
        self->GetThreadName(name);
        stream_ << "Thread " << name << " (id: " << std::dec << self->GetThreadId()
                << ") force interpreter count " << self->ForceInterpreterCount() << "\n";
      }
      // Increment this after unlocking the mutex so we won't race its destructor.
      cnt_++;
    }

    void WaitForCount(size_t threads) {
      while (cnt_.load() != threads) {
        sched_yield();
      }
    }

   private:
    std::atomic<size_t> cnt_;
    std::ostream& stream_;
    std::mutex& mu_;
  };

  std::mutex mu;
  DumpThreadDeoptCount dtdc(stream, mu);
  auto func = [](art::Thread* thread, void* ctx) {
    reinterpret_cast<DumpThreadDeoptCount*>(ctx)->Run(thread);
  };
  art::Runtime::Current()->GetThreadList()->ForEach(func, &dtdc);
}

void DeoptManager::FinishSetup() {
  art::Thread* self = art::Thread::Current();
  art::MutexLock mu(self, deoptimization_status_lock_);

  art::Runtime* runtime = art::Runtime::Current();
  // See if we need to do anything.
  if (!runtime->IsJavaDebuggable()) {
    // See if we can enable all JVMTI functions. If this is false, only kArtTiVersion agents can be
    // retrieved and they will all be best-effort.
    if (PhaseUtil::GetPhaseUnchecked() == JVMTI_PHASE_ONLOAD) {
      // We are still early enough to change the compiler options and get full JVMTI support.
      LOG(INFO) << "Openjdkjvmti plugin loaded on a non-debuggable runtime. Changing runtime to "
                << "debuggable state. Please pass '--debuggable' to dex2oat and "
                << "'-Xcompiler-option --debuggable' to dalvikvm in the future.";
      DCHECK(runtime->GetJit() == nullptr) << "Jit should not be running yet!";
      runtime->AddCompilerOption("--debuggable");
      runtime->SetJavaDebuggable(true);
    } else {
      LOG(WARNING) << "Openjdkjvmti plugin was loaded on a non-debuggable Runtime. Plugin was "
                   << "loaded too late to change runtime state to DEBUGGABLE. Only kArtTiVersion "
                   << "(0x" << std::hex << kArtTiVersion << ") environments are available. Some "
                   << "functionality might not work properly.";
      if (runtime->GetJit() == nullptr &&
          runtime->GetJITOptions()->UseJitCompilation() &&
          !runtime->GetInstrumentation()->IsForcedInterpretOnly()) {
        // If we don't have a jit we should try to start the jit for performance reasons. We only
        // need to do this for late attach on non-debuggable processes because for debuggable
        // processes we already rely on jit and we cannot force this jit to start if we are still in
        // OnLoad since the runtime hasn't started up sufficiently. This is only expected to happen
        // on userdebug/eng builds.
        LOG(INFO) << "Attempting to start jit for openjdkjvmti plugin.";
        // Note: use rwx allowed = true, because if this is the system server, we will not be
        //       allowed to allocate any JIT code cache, anyways.
        runtime->CreateJitCodeCache(/*rwx_memory_allowed=*/true);
        runtime->CreateJit();
        if (runtime->GetJit() == nullptr) {
          LOG(WARNING) << "Could not start jit for openjdkjvmti plugin. This process might be "
                       << "quite slow as it is running entirely in the interpreter. Try running "
                       << "'setenforce 0' and restarting this process.";
        }
      }
    }
    runtime->DeoptimizeBootImage();
  }
}

bool DeoptManager::MethodHasBreakpoints(art::ArtMethod* method) {
  art::MutexLock lk(art::Thread::Current(), breakpoint_status_lock_);
  return MethodHasBreakpointsLocked(method);
}

bool DeoptManager::MethodHasBreakpointsLocked(art::ArtMethod* method) {
  auto elem = breakpoint_status_.find(method);
  return elem != breakpoint_status_.end() && elem->second != 0;
}

void DeoptManager::RemoveDeoptimizeAllMethods() {
  art::Thread* self = art::Thread::Current();
  art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
  deoptimization_status_lock_.ExclusiveLock(self);
  RemoveDeoptimizeAllMethodsLocked(self);
}

void DeoptManager::AddDeoptimizeAllMethods() {
  art::Thread* self = art::Thread::Current();
  art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
  deoptimization_status_lock_.ExclusiveLock(self);
  AddDeoptimizeAllMethodsLocked(self);
}

void DeoptManager::AddMethodBreakpoint(art::ArtMethod* method) {
  DCHECK(method->IsInvokable());
  DCHECK(!method->IsProxyMethod()) << method->PrettyMethod();
  DCHECK(!method->IsNative()) << method->PrettyMethod();

  art::Thread* self = art::Thread::Current();
  method = method->GetCanonicalMethod();
  bool is_default = method->IsDefault();

  art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
  deoptimization_status_lock_.ExclusiveLock(self);
  {
    breakpoint_status_lock_.ExclusiveLock(self);

    DCHECK_GT(deopter_count_, 0u) << "unexpected deotpimization request";

    if (MethodHasBreakpointsLocked(method)) {
      // Don't need to do anything extra.
      breakpoint_status_[method]++;
      // Another thread might be deoptimizing the very method we just added new breakpoints for.
      // Wait for any deopts to finish before moving on.
      breakpoint_status_lock_.ExclusiveUnlock(self);
      WaitForDeoptimizationToFinish(self);
      return;
    }
    breakpoint_status_[method] = 1;
    breakpoint_status_lock_.ExclusiveUnlock(self);
  }
  auto instrumentation = art::Runtime::Current()->GetInstrumentation();
  if (instrumentation->IsForcedInterpretOnly()) {
    // We are already interpreting everything so no need to do anything.
    deoptimization_status_lock_.ExclusiveUnlock(self);
    return;
  } else if (is_default) {
    AddDeoptimizeAllMethodsLocked(self);
  } else {
    PerformLimitedDeoptimization(self, method);
  }
}

void DeoptManager::RemoveMethodBreakpoint(art::ArtMethod* method) {
  DCHECK(method->IsInvokable()) << method->PrettyMethod();
  DCHECK(!method->IsProxyMethod()) << method->PrettyMethod();
  DCHECK(!method->IsNative()) << method->PrettyMethod();

  art::Thread* self = art::Thread::Current();
  method = method->GetCanonicalMethod();
  bool is_default = method->IsDefault();

  art::ScopedThreadSuspension sts(self, art::ThreadState::kSuspended);
  // Ideally we should do a ScopedSuspendAll right here to get the full mutator_lock_ that we might
  // need but since that is very heavy we will instead just use a condition variable to make sure we
  // don't race with ourselves.
  deoptimization_status_lock_.ExclusiveLock(self);
  bool is_last_breakpoint;
  {
    art::MutexLock mu(self, breakpoint_status_lock_);

    DCHECK_GT(deopter_count_, 0u) << "unexpected deotpimization request";
    DCHECK(MethodHasBreakpointsLocked(method)) << "Breakpoint on a method was removed without "
                                              << "breakpoints present!";
    breakpoint_status_[method] -= 1;
    is_last_breakpoint = (breakpoint_status_[method] == 0);
  }
  auto instrumentation = art::Runtime::Current()->GetInstrumentation();
  if (UNLIKELY(instrumentation->IsForcedInterpretOnly())) {
    // We don't need to do anything since we are interpreting everything anyway.
    deoptimization_status_lock_.ExclusiveUnlock(self);
    return;
  } else if (is_last_breakpoint) {
    if (UNLIKELY(is_default)) {
      RemoveDeoptimizeAllMethodsLocked(self);
    } else {
      PerformLimitedUndeoptimization(self, method);
    }
  } else {
    // Another thread might be deoptimizing the very methods we just removed breakpoints from. Wait
    // for any deopts to finish before moving on.
    WaitForDeoptimizationToFinish(self);
  }
}

void DeoptManager::WaitForDeoptimizationToFinishLocked(art::Thread* self) {
  while (performing_deoptimization_) {
    deoptimization_condition_.Wait(self);
  }
}

void DeoptManager::WaitForDeoptimizationToFinish(art::Thread* self) {
  WaitForDeoptimizationToFinishLocked(self);
  deoptimization_status_lock_.ExclusiveUnlock(self);
}

// Users should make sure that only gc-critical-section safe code is used while a
// ScopedDeoptimizationContext exists.
class ScopedDeoptimizationContext : public art::ValueObject {
 public:
  ScopedDeoptimizationContext(art::Thread* self, DeoptManager* deopt)
      RELEASE(deopt->deoptimization_status_lock_)
      ACQUIRE(art::Locks::mutator_lock_)
      ACQUIRE(art::Roles::uninterruptible_)
      : self_(self),
        deopt_(deopt),
        critical_section_(self_, "JVMTI Deoptimizing methods"),
        uninterruptible_cause_(nullptr) {
    deopt_->WaitForDeoptimizationToFinishLocked(self_);
    DCHECK(!deopt->performing_deoptimization_)
        << "Already performing deoptimization on another thread!";
    // Use performing_deoptimization_ to keep track of the lock.
    deopt_->performing_deoptimization_ = true;
    deopt_->deoptimization_status_lock_.Unlock(self_);
    uninterruptible_cause_ = critical_section_.Enter(art::gc::kGcCauseInstrumentation,
                                                     art::gc::kCollectorTypeCriticalSection);
    art::Runtime::Current()->GetThreadList()->SuspendAll("JMVTI Deoptimizing methods",
                                                         /*long_suspend=*/ false);
  }

  ~ScopedDeoptimizationContext()
      RELEASE(art::Locks::mutator_lock_)
      RELEASE(art::Roles::uninterruptible_) {
    // Can be suspended again.
    critical_section_.Exit(uninterruptible_cause_);
    // Release the mutator lock.
    art::Runtime::Current()->GetThreadList()->ResumeAll();
    // Let other threads know it's fine to proceed.
    art::MutexLock lk(self_, deopt_->deoptimization_status_lock_);
    deopt_->performing_deoptimization_ = false;
    deopt_->deoptimization_condition_.Broadcast(self_);
  }

 private:
  art::Thread* self_;
  DeoptManager* deopt_;
  art::gc::GCCriticalSection critical_section_;
  const char* uninterruptible_cause_;
};

void DeoptManager::AddDeoptimizeAllMethodsLocked(art::Thread* self) {
  global_deopt_count_++;
  if (global_deopt_count_ == 1) {
    PerformGlobalDeoptimization(self);
  } else {
    WaitForDeoptimizationToFinish(self);
  }
}

void DeoptManager::RemoveDeoptimizeAllMethodsLocked(art::Thread* self) {
  DCHECK_GT(global_deopt_count_, 0u) << "Request to remove non-existent global deoptimization!";
  global_deopt_count_--;
  if (global_deopt_count_ == 0) {
    PerformGlobalUndeoptimization(self);
  } else {
    WaitForDeoptimizationToFinish(self);
  }
}

void DeoptManager::PerformLimitedDeoptimization(art::Thread* self, art::ArtMethod* method) {
  ScopedDeoptimizationContext sdc(self, this);
  art::Runtime::Current()->GetInstrumentation()->Deoptimize(method);
}

void DeoptManager::PerformLimitedUndeoptimization(art::Thread* self, art::ArtMethod* method) {
  ScopedDeoptimizationContext sdc(self, this);
  art::Runtime::Current()->GetInstrumentation()->Undeoptimize(method);
}

void DeoptManager::PerformGlobalDeoptimization(art::Thread* self) {
  ScopedDeoptimizationContext sdc(self, this);
  art::Runtime::Current()->GetInstrumentation()->DeoptimizeEverything(
      kDeoptManagerInstrumentationKey);
}

void DeoptManager::PerformGlobalUndeoptimization(art::Thread* self) {
  ScopedDeoptimizationContext sdc(self, this);
  art::Runtime::Current()->GetInstrumentation()->UndeoptimizeEverything(
      kDeoptManagerInstrumentationKey);
}

jvmtiError DeoptManager::AddDeoptimizeThreadMethods(art::ScopedObjectAccessUnchecked& soa, jthread jtarget) {
  art::Locks::thread_list_lock_->ExclusiveLock(soa.Self());
  art::Thread* target = nullptr;
  jvmtiError err = OK;
  if (!ThreadUtil::GetNativeThread(jtarget, soa, &target, &err)) {
    art::Locks::thread_list_lock_->ExclusiveUnlock(soa.Self());
    return err;
  }
  // We don't need additional locking here because we hold the Thread_list_lock_.
  if (target->IncrementForceInterpreterCount() == 1) {
    struct DeoptClosure : public art::Closure {
     public:
      explicit DeoptClosure(DeoptManager* manager) : manager_(manager) {}
      void Run(art::Thread* self) override REQUIRES_SHARED(art::Locks::mutator_lock_) {
        manager_->DeoptimizeThread(self);
      }

     private:
      DeoptManager* manager_;
    };
    DeoptClosure c(this);
    target->RequestSynchronousCheckpoint(&c);
  } else {
    art::Locks::thread_list_lock_->ExclusiveUnlock(soa.Self());
  }
  return OK;
}

jvmtiError DeoptManager::RemoveDeoptimizeThreadMethods(art::ScopedObjectAccessUnchecked& soa, jthread jtarget) {
  art::MutexLock mu(soa.Self(), *art::Locks::thread_list_lock_);
  art::Thread* target = nullptr;
  jvmtiError err = OK;
  if (!ThreadUtil::GetNativeThread(jtarget, soa, &target, &err)) {
    return err;
  }
  // We don't need additional locking here because we hold the Thread_list_lock_.
  DCHECK_GT(target->ForceInterpreterCount(), 0u);
  target->DecrementForceInterpreterCount();
  return OK;
}

static constexpr const char* kInstrumentationKey = "JVMTI_DeoptRequester";

void DeoptManager::RemoveDeoptimizationRequester() {
  art::Thread* self = art::Thread::Current();
  art::ScopedThreadStateChange sts(self, art::ThreadState::kSuspended);
  deoptimization_status_lock_.ExclusiveLock(self);
  DCHECK_GT(deopter_count_, 0u) << "Removing deoptimization requester without any being present";
  deopter_count_--;
  if (deopter_count_ == 0) {
    ScopedDeoptimizationContext sdc(self, this);
    art::Runtime::Current()->GetInstrumentation()->DisableDeoptimization(kInstrumentationKey);
    return;
  } else {
    deoptimization_status_lock_.ExclusiveUnlock(self);
  }
}

void DeoptManager::AddDeoptimizationRequester() {
  art::Thread* self = art::Thread::Current();
  art::ScopedThreadStateChange stsc(self, art::ThreadState::kSuspended);
  deoptimization_status_lock_.ExclusiveLock(self);
  deopter_count_++;
  deoptimization_status_lock_.ExclusiveUnlock(self);
}

void DeoptManager::DeoptimizeThread(art::Thread* target) {
  // We might or might not be running on the target thread (self) so get Thread::Current
  // directly.
  art::ScopedThreadSuspension sts(art::Thread::Current(), art::ThreadState::kSuspended);
  art::gc::ScopedGCCriticalSection sgccs(art::Thread::Current(),
                                         art::gc::GcCause::kGcCauseDebugger,
                                         art::gc::CollectorType::kCollectorTypeDebugger);
  art::ScopedSuspendAll ssa("Instrument thread stack");
  // Prepare the stack so methods can be deoptimized as and when required.
  // This by itself doesn't cause any methods to deoptimize but enables
  // deoptimization on demand.
  art::Runtime::Current()->GetInstrumentation()->InstrumentThreadStack(
      target,
      /* deopt_all_frames= */ false);
}

extern DeoptManager* gDeoptManager;
DeoptManager* DeoptManager::Get() {
  return gDeoptManager;
}

}  // namespace openjdkjvmti