/*
 * Copyright (c) 2014, 2015, Dynatrace and/or its affiliates. All rights reserved.
 *
 * This file is part of the Lock Contention Tracing Subsystem for the HotSpot
 * Virtual Machine, which is developed at Christian Doppler Laboratory on
 * Monitoring and Evolution of Very-Large-Scale Software Systems. Please
 * contact us at <http://mevss.jku.at/> if you need additional information
 * or have any questions.
 *
 * 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, see <http://www.gnu.org/licenses/>.
 *
 */

#include "evtrace/traceStack.hpp"

#include "evtrace/traceEvents.hpp"
#include "evtrace/traceMetadata.hpp"

#include "runtime/vframe.hpp"
#include "runtime/init.hpp"

//
// TraceStackBuilder
//

void TraceStackBuilder::add(const TraceStackFrame &f) {
  assert(!is_full(), "already full");
  _frames[_count] = f;
  _hash ^= f.hash();
  _count++;
}

void TraceStackBuilder::add_frame(const frame *fr) {
  TraceStackFrame f;
  f.is_compiled = fr->cb()->is_nmethod();
  if (f.is_compiled) {
    assert(fr->is_compiled_frame() || fr->is_native_frame(), "unsupported frame type");
    f.compiled.pc = fr->pc();
    f.compiled.nm = (nmethod *) fr->cb();
  } else {
    assert(fr->is_interpreted_frame(), "unsupported frame type");
    f.interpreted.method = fr->interpreter_frame_method();
    f.interpreted.bci = fr->interpreter_frame_bci();
  }
  add(f);
}

bool TraceStackBuilder::range_equals(size_t offset, const CachedTraceStack *cts, size_t cts_offset, size_t count) const {
  for (size_t i = 0; i < count; i++) {
    if (!frame_at(offset + i)->equals(*cts->frame_at(cts_offset + i))) {
      return false;
    }
  }
  return true;
}

//
// CachedTraceStack
//

CachedTraceStack *CachedTraceStack::create(TraceTypes::stack_id id, const CompositeTraceStack &ts) {
  assert (in_bytes(byte_offset_of(CachedTraceStack, _frames)) == sizeof(CachedTraceStack),
      "variable-sized frame array must be last field");
  return new (ts.count()) CachedTraceStack(id, ts);
}

void* CachedTraceStack::operator new(size_t size, size_t nframes) throw () {
  return CHeapObj<mtEventTracing>::operator new(size + sizeof(_frames[0]) * nframes, CALLER_PC);
}

void CachedTraceStack::operator delete(void* p) {
  CHeapObj<mtEventTracing>::operator delete(p);
}

CachedTraceStack::CachedTraceStack(TraceTypes::stack_id id, const CompositeTraceStack& ts)
  : _id(id),
    _count(ts.count()),
    _hash(ts.hash()),
    _truncated(ts.is_truncated()),
    _valid(true)
{
  for (size_t i = 0; i < ts.count(); i++) {
    _frames[i] = *ts.frame_at(i);
  }
}

bool CachedTraceStack::has_interpreted_method_from_classloader(const ClassLoaderData* loader) const {
  assert(is_valid(), "sanity");
  for (size_t i = 0; i < _count; i++) {
    if (!_frames[i].is_compiled && _frames[i].interpreted.method->method_holder()->class_loader_data() == loader) {
      return true;
    }
  }
  return false;
}

bool CachedTraceStack::has_nmethod(const nmethod *nm) const {
  assert(is_valid(), "sanity");
  for (size_t i = 0; i < _count; i++) {
    if (_frames[i].is_compiled && _frames[i].compiled.nm == nm) {
      return true;
    }
  }
  return false;
}

bool CachedTraceStack::range_equals(size_t offset, const CachedTraceStack *other, size_t other_offset, size_t count) const {
  for (size_t i = 0; i < count; i++) {
    if (!frame_at(offset + i)->equals(*other->frame_at(other_offset + i))) {
      return false;
    }
  }
  return true;
}

//
// CompositeTraceStack
//

void CompositeTraceStack::set_bottom(const CachedTraceStack *bottom, size_t offset) {
  _hash = _top.hash();
  _count = _top.count();
  _truncated = _top.is_truncated();

  _bottom = bottom;
  _bottom_offset = offset;
  if (bottom != NULL) {
    if (_top.count() < EventTracingStackDepthLimit) {
      assert(!_top.is_truncated(), "missing frames between top and bottom");
      _count += bottom->count() - offset;
      _truncated = _truncated || bottom->is_truncated();
      if (_count > EventTracingStackDepthLimit) {
        _truncated = true;
        _count = EventTracingStackDepthLimit;
      }
      _hash ^= bottom->hash();
      // drop frames before offset from hash
      for (size_t i = 0; i < offset; i++) {
        _hash ^= bottom->frame_at(i)->hash();
      }
      // drop truncated frames from hash
      for (size_t i = EventTracingStackDepthLimit - _top.count() + offset; i < _bottom->count(); i++) {
        _hash ^= bottom->frame_at(i)->hash();
      }
    } else {
      _truncated = _truncated || (bottom->count() > offset);
    }
  }

#ifdef ASSERT
  intptr_t h = 0;
  for (size_t i = 0; i < count(); i++) {
    h ^= frame_at(i)->hash();
  }
  assert(h == hash(), "hash mismatch");
#endif
}

bool CompositeTraceStack::equals(const CachedTraceStack* cts) const {
  if (hash() != cts->hash() || count() != cts->count() || is_truncated() != cts->is_truncated()) {
    return false;
  }
  return _top.range_equals(0, cts, 0, _top.count())
      && (_bottom == NULL || _bottom->range_equals(_bottom_offset, cts, _top.count(), count() - _top.count()));
}

bool CompositeTraceStack::equals(const CompositeTraceStack &other) const {
  if (hash() != other.hash() || count() != other.count() || is_truncated() != other.is_truncated()) {
    return false;
  }
  for (size_t i = 0; i < count(); i++) {
    if (!frame_at(i)->equals(*other.frame_at(i))) {
      return false;
    }
  }
  return true;
}

//
// TraceStackCache
//

TraceStackCache::TraceStackCache(TraceMetadata *tm)
{
  _metadata = tm;

  _table = NULL;
  _count = 0;
  _has_invalid_stacks = false;

  _lookup_counter = _lookup_miss_counter = _lookup_collision_counter = _probe_counter = _probe_collision_counter = 0;

  _size = (1 << 12);
  assert(is_power_of_2(_size), "sanity");
  _table = (CachedTraceStack **) os::malloc(_size * sizeof(_table[0]), mtEventTracing, CURRENT_PC);
  memset(_table, 0, _size * sizeof(_table[0]));
}

TraceStackCache::~TraceStackCache() {
  for (size_t i = 0; i < _size; i++) {
    CachedTraceStack *p = _table[i];
    while (p != NULL) {
      CachedTraceStack *next = p->cache_next();
      delete p;
      p = next;
    }
  }
  os::free(_table, mtEventTracing);
}

void TraceStackCache::add_for_rehash(CachedTraceStack *cts) {
  const size_t mask = (_size - 1);
  intptr_t index = cts->hash() & mask;
  cts->set_cache_next(_table[index]);
  _table[index] = cts;
  _count++;
}

inline void TraceStackCache::update_counters_after_lookup(bool present, jlong probes, jlong collisions) {
  if (EnableEventTracingDiagnostics) {
    Atomic::inc_ptr(&_lookup_counter);
    Atomic::add_ptr(probes, &_probe_counter);
    if (!present) {
      Atomic::inc_ptr(&_lookup_miss_counter);
    }
    if (collisions > 0) {
      Atomic::inc_ptr(&_lookup_collision_counter);
      Atomic::add_ptr(collisions, &_probe_collision_counter);
    }
  }
}

const CachedTraceStack * TraceStackCache::get_or_try_add(const CompositeTraceStack &ts, bool &known, TraceTypes::stack_id preallocated_id) {
  jlong probes = 0, collisions = 0;

  CachedTraceStack *created = NULL;

  const size_t mask = (_size - 1);
  const size_t index = ts.hash() & mask;
  // XXX: probably need barriers here on non-x86
  for(;;) {
    CachedTraceStack *head = _table[index];
    if (head == NULL) {
      probes++;
    }
    CachedTraceStack *p = head;
    while (p != NULL) {
      probes++;
      if (ts.hash() == p->hash()) {
        if (ts.equals(p)) {
          delete created;
          known = true;
          update_counters_after_lookup(true, probes, collisions);
          return p;
        } else {
          collisions++;
        }
      }
      p = p->cache_next();
    }
    // not found
    if (created == NULL) {
      TraceTypes::stack_id id = preallocated_id;
      if (id == 0) {
        id = _metadata->next_stack_id();
      }
      created = CachedTraceStack::create(id, ts);
    }
    created->set_cache_next(head);
    if (Atomic::cmpxchg_ptr(created, &_table[index], head) == head) {
      Atomic::inc_ptr(&_count);
      known = false;
      update_counters_after_lookup(false, probes, collisions);
      return created;
    }
    // head of collision chain changed: walk the entire chain again in the next
    // next iteration to check whether the stack trace has been inserted by
    // another thread (head is not enough, multiple threads may have inserted)
  }
}

class TraceStackCache::CachedTraceStackPredicate {
public:
  virtual bool test(CachedTraceStack *cts) = 0;
};

inline void TraceStackCache::purge_matches(TraceStackCache::CachedTraceStackPredicate *pr) {
  if (EnableEventTracingDiagnostics) {
    _purge_timer.start();
  }

  for (size_t i = 0; i < _size; i++) {
    CachedTraceStack *p = _table[i];
    while (p != NULL) {
      if (p->is_valid() && pr->test(p)) {
        p->invalidate();
        _has_invalid_stacks = true;
      }
      p = p->cache_next();
    }
  }

  if (EnableEventTracingDiagnostics) {
    _purge_timer.stop();
  }
}

class TraceStackCache::UnloadingClassPredicate : public TraceStackCache::CachedTraceStackPredicate {
  const ClassLoaderData *_loader;
public:
  UnloadingClassPredicate(const ClassLoaderData *loader) : _loader(loader) { }
  virtual bool test(CachedTraceStack *stack) {
    return stack->has_interpreted_method_from_classloader(_loader);
  }
};

void TraceStackCache::purge_unloading_classes(const ClassLoaderData* loader) {
  assert(SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread(), "must be done in VM thread at safepoint");

  // NOTE: only purges stack traces with *interpreted* frames that refer to
  // unloading classes. nmethods with code from unloaded classes are unloaded
  // in a later step, at which point we also unload the stack traces that
  // contain those nmethods.
  UnloadingClassPredicate pr(loader);
  purge_matches(&pr);
}

class TraceStackCache::UnloadingNmethodPredicate : public TraceStackCache::CachedTraceStackPredicate {
  const nmethod *_nmethod;
public:
  UnloadingNmethodPredicate(const nmethod *nm) : _nmethod(nm) { }
  virtual bool test(CachedTraceStack *stack) {
    return stack->has_nmethod(_nmethod);
  }
};

void TraceStackCache::purge_unloading_nmethod(const nmethod *nm) {
  UnloadingNmethodPredicate pr(nm);
  purge_matches(&pr);
}

class TraceStackCache::AnyPredicate : public TraceStackCache::CachedTraceStackPredicate {
public:
  virtual bool test(CachedTraceStack *stack) {
    return true;
  }
};

void TraceStackCache::purge_all() {
  AnyPredicate pr;
  purge_matches(&pr);
}

void TraceStackCache::do_maintenance() {
  assert(SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread(), "must be done in VM thread at safepoint");

  bool should_grow = (_count / (float) _size > 0.7f);
  if (should_grow || has_invalid_stacks()) {
    if (EnableEventTracingDiagnostics) {
      _maintenance_timer.start();
    }

    CachedTraceStack **old_table = _table;
    size_t old_capacity = _size;

    if (should_grow) {
      _size <<= 1;
      assert(is_power_of_2(_size), "sanity");
    }
    _count = 0;
    _table = (CachedTraceStack **) os::malloc(_size * sizeof(_table[0]), mtEventTracing, CURRENT_PC);
    memset(_table, 0, _size * sizeof(_table[0]));
    for (size_t i = 0; i < old_capacity; i++) {
      CachedTraceStack *p = old_table[i];
      while (p != NULL) {
        CachedTraceStack *next = p->cache_next();
        if (p->is_valid()) {
          add_for_rehash(p);
        } else {
          delete p;
        }
        p = next;
      }
    }
    os::free(old_table, mtEventTracing);

    if (EnableEventTracingDiagnostics) {
      _maintenance_timer.stop();
    }

    _has_invalid_stacks = false;
  }
}

void TraceStackCache::reset_stats() {
  _lookup_counter = _lookup_miss_counter = _lookup_collision_counter = _probe_counter = _probe_collision_counter = 0;

  // these are only used in a safepoint: we should be fine either way
  _purge_timer.reset();
  _maintenance_timer.reset();
}