IdentifiableCacheBase.cxx

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/*
  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
*/
 
// $Id: IdentifiableCacheBase.cxx 791541 2017-01-09 10:43:53Z smh $
 
// null --- default state.
// ABORTED -- conversion failed or returned null
// ptr > null && ptr < ABORTED --- Have payload
// INVALID --- Conversion in progress or intention to add soon.
 
#include "EventContainers/IdentifiableCacheBase.h"
#include "CxxUtils/AthUnlikelyMacros.h"
#include <bit>
 
namespace EventContainers {
 
const void* const INVALID = std::bit_cast<const void*>(IdentifiableCacheBase::INVALIDflag);
const void* const ABORTED = std::bit_cast<const void*>(IdentifiableCacheBase::ABORTEDflag);
 
 
 
IdentifiableCacheBase::IdentifiableCacheBase (IdentifierHash maxHash,
                                              const IMaker* maker)
  : m_vec(maxHash),
    m_maker (maker),
    m_currentHashes(0)
{
}
 
 
IdentifiableCacheBase::~IdentifiableCacheBase()=default;
 
int IdentifiableCacheBase::tryLock(IdentifierHash hash, IDC_WriteHandleBase &lock, std::vector<IdentifierHash> &wait){
   const void *ptr1 =nullptr;
 
   if(m_vec[hash].compare_exchange_strong(ptr1, INVALID, std::memory_order_relaxed, std::memory_order_relaxed)){//atomic swap (replaces ptr1 with value)
      //First call
      //Setup the IDC_WriteHandle to "lock" on this hash's pointer
      lock.LockOn(&m_vec[hash]);
      return 0;
   }
 
   if(ptr1 == INVALID){
      //Second call while not finished
      wait.emplace_back(hash);
      return 1;
   }
   if(ptr1 == ABORTED) return 3;
   return 2;   //Already completed
}
 
 
void IdentifiableCacheBase::clear (deleter_f* deleter)
{
  size_t s = m_vec.size();
  if(0 != m_currentHashes.load(std::memory_order_relaxed)){
     for (size_t i=0; i<s ;i++) {
       const void* ptr = m_vec[i].load(std::memory_order_relaxed);
       m_vec[i].store(nullptr, std::memory_order_relaxed);
       if (ptr && ptr < ABORTED){
         deleter (ptr);
      }
     }
     m_currentHashes.store(0, std::memory_order_relaxed);
  }else{
    for (size_t i=0; i<s ;i++) m_vec[i].store(nullptr, std::memory_order_relaxed);//Need to clear incase of aborts
  }
}
 
 
//Does not lock or clear atomics to allow faster destruction
void IdentifiableCacheBase::cleanUp (deleter_f* deleter)
{
  std::atomic_thread_fence(std::memory_order_acquire);
  if(0 != m_currentHashes.load(std::memory_order_relaxed)){ //Reduce overhead if cache was unused
    size_t s = m_vec.size();
    for (size_t i=0; i<s ;i++) {
      const void* p = m_vec[i].load(std::memory_order_relaxed);
      if(p && p < ABORTED) deleter (p);
    }
  }
}
 
int IdentifiableCacheBase::itemAborted (IdentifierHash hash){
   const void* p = m_vec[hash].load(std::memory_order_relaxed); //Relaxed because it is not returning a pointer to anything
   return (p == ABORTED);
}
 
 
int IdentifiableCacheBase::itemInProgress (IdentifierHash hash){
   const void* p = m_vec[hash].load(std::memory_order_relaxed); //Relaxed because it is not returning a pointer to anything
   return (p == INVALID);
}
 
 
const void* IdentifiableCacheBase::find (IdentifierHash hash) noexcept
{
  if (ATH_UNLIKELY(hash >= m_vec.size())) return nullptr;
  const void* p = m_vec[hash].load(std::memory_order_acquire);
  if (p >= ABORTED)
    return nullptr;
  return p;
}
 
const void* IdentifiableCacheBase::waitFor(IdentifierHash hash)
{
   std::atomic<const void*> &myatomic = m_vec[hash];
   const void* item = myatomic.load(std::memory_order_acquire);
   //Wait until pointer is set then retrieve and verify
   while(item == INVALID){//Loop to check for spurious wakeups
      myatomic.wait(item, std::memory_order_relaxed);
      item = myatomic.load(std::memory_order_acquire);
   }
   return item;
}
 
const void* IdentifiableCacheBase::findWait (IdentifierHash hash)
{
  if (ATH_UNLIKELY(hash >= m_vec.size())) return nullptr;
  const void* p = waitFor(hash);
  if(p>=ABORTED) return nullptr;
  return p;
}
 
void IdentifiableCacheBase::notifyHash(IdentifierHash hash)
{
    m_vec[hash].notify_all();
}
 
const void* IdentifiableCacheBase::get (IdentifierHash hash)
{
  // If it's there already, return directly without locking.
  const void* ptr = nullptr;
  if (ATH_UNLIKELY(hash >= m_vec.size())) return ptr;
 
  if(m_vec[hash].compare_exchange_strong(ptr, INVALID) ) {//Exchanges ptr with current value!!
     // Make the payload.
     if(m_maker == nullptr){
        m_vec[hash].store( ABORTED );
        return nullptr;
     }
     uniqueLock lock(m_mutex, std::defer_lock);
     if(!m_maker->m_IsReEntrant) lock.lock();//Allow reentrant or non reentrant makers
 
     try {
       ptr = m_maker->typelessMake (hash).release();
     }
     catch (...) {
       // FIXME: Can this be done with RAII?
       notifyHash(hash);
       throw;
     }
     assert(m_vec[hash] == INVALID);
     if(ptr){
        m_vec[hash].store( ptr );
        m_currentHashes++;
     }else{
        m_vec[hash].store( ABORTED );
     }
     notifyHash(hash);
  }
  else if(ptr == INVALID){
     ptr= waitFor(hash);
  }
  if(ptr == ABORTED) return nullptr;
  assert(ptr < ABORTED);
  return ptr;
}
 
void IdentifiableCacheBase::createSet (const std::vector<IdentifierHash>& hashes, std::vector<bool> &mask){
   assert(mask.size() == fullSize());
   for(IdentifierHash hash : hashes){
      const void* ptr = get(hash);
      if(ptr !=nullptr) mask[hash] = true;
   }
}
 
 
size_t IdentifiableCacheBase::numberOfHashes()
{
  return m_currentHashes.load(std::memory_order_relaxed); //Not to be used for syncing
}
 
std::vector<IdentifierHash> IdentifiableCacheBase::ids()
{
  std::vector<IdentifierHash> ret;
  ret.reserve (m_currentHashes.load(std::memory_order_relaxed));
  size_t s = m_vec.size();
  for (size_t i =0; i<s; i++) {
    const void* p = m_vec[i].load(std::memory_order_relaxed);
    if (p && p < ABORTED)
      ret.push_back (i);
  }
  return ret;
}
 
 
std::pair<bool, const void*> IdentifiableCacheBase::add (IdentifierHash hash, const void* p) noexcept
{
  if (ATH_UNLIKELY(hash >= m_vec.size())) return std::make_pair(false, nullptr);
  if(p==nullptr) return std::make_pair(false, nullptr);
  const void* nul=nullptr;
  if(m_vec[hash].compare_exchange_strong(nul, p, std::memory_order_release, std::memory_order_relaxed)){
     m_currentHashes.fetch_add(1, std::memory_order_relaxed);
     return std::make_pair(true, p);
  }
  const void* invalid = INVALID;
  if(m_vec[hash].compare_exchange_strong(invalid, p, std::memory_order_release, std::memory_order_acquire)){
     m_currentHashes.fetch_add(1, std::memory_order_relaxed);
     notifyHash(hash);
     return std::make_pair(true, p);
  }
  return std::make_pair(false, invalid);
}
 
 
std::pair<bool, const void*> IdentifiableCacheBase::addLock (IdentifierHash hash, const void* p) noexcept
{ //Same as method above except we check for invalid state first,
  // more optimal for calling using writehandle lock method
  assert(hash < m_vec.size());
  if(p==nullptr) return std::make_pair(false, nullptr);
  const void* invalid = INVALID;
  if(m_vec[hash].compare_exchange_strong(invalid, p, std::memory_order_release, std::memory_order_relaxed)){
     m_currentHashes.fetch_add(1, std::memory_order_relaxed);
     notifyHash(hash);
     return std::make_pair(true, p);
  }
  const void* nul=nullptr;
  if(m_vec[hash].compare_exchange_strong(nul, p, std::memory_order_release, std::memory_order_acquire)){
     m_currentHashes.fetch_add(1, std::memory_order_relaxed);
     return std::make_pair(true, p);
  }
  return std::make_pair(false, nul);
}
 
std::pair<bool, const void*> IdentifiableCacheBase::addLock (IdentifierHash hash,
                                 void_unique_ptr p) noexcept
{
  std::pair<bool, const void*> b = addLock(hash, p.get());
  if(b.first) p.release();
  return b;
}
 
 
std::pair<bool, const void*> IdentifiableCacheBase::add (IdentifierHash hash,
                                 void_unique_ptr p) noexcept
{
  std::pair<bool, const void*> b = add(hash, p.get());
  if(b.first) p.release();
  return b;
}
 
 
 
} // namespace EventContainers