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/** \file     NoMallocThreadPool.cpp

    \brief    thread pool

*/

#include "NoMallocThreadPool.h"

#ifdef HAVE_PTHREADS

#  include <pthread.h>

#  define THREAD_MIN_STACK_SIZE 1024 * 1024

#endif

//! \ingroup Utilities

//! \{

namespace vvenc {

#if ENABLE_TIME_PROFILING_MT_MODE

thread_local std::unique_ptr<TProfiler> ptls;

#endif

NoMallocThreadPool::NoMallocThreadPool( int numThreads, const char * threadPoolName, const VVEncCfg* encCfg )

  : m_poolName( threadPoolName )

{

  if( numThreads < 0 )

  {

    numThreads = std::thread::hardware_concurrency();

  }

  for( int i = 0; i < numThreads; ++i )

  {

    m_threads.emplace_back( &NoMallocThreadPool::threadProc, this, i, *encCfg );

  }

}

NoMallocThreadPool::~NoMallocThreadPool()

{

  m_exitThreads = true;

  waitForThreads();

}

bool NoMallocThreadPool::processTasksOnMainThread()

{

  CHECK( m_threads.size() != 0, "should not be used with multiple threads" );

  bool         progress      = false;

  TaskIterator firstFailedIt = m_tasks.end();

  for( auto taskIt = findNextTask( 0, m_tasks.begin() ); taskIt.isValid(); taskIt = findNextTask( 0, taskIt ) )

  {

    const bool success = processTask( 0, *taskIt );

    progress |= success;

    if( taskIt == firstFailedIt )

    {

      if( success )

      {

        // first failed was successful -> reset

        firstFailedIt = m_tasks.end();

      }

      else if( progress )

      {

        // reset progress, try another round

        progress = false;

      }

      else

      {

        // no progress -> exit

        break;

      }

    }

    else if( !success && !firstFailedIt.isValid() )

    {

      firstFailedIt = taskIt;

    }

  }

  // return true if all done (-> false if some tasks blocked due to barriers)

  return std::all_of( m_tasks.begin(), m_tasks.end(), []( Slot& t ) { return t.state == FREE; } );

}

void NoMallocThreadPool::shutdown( bool block )

{

  m_exitThreads = true;

  if( block )

  {

    waitForThreads();

  }

}

void NoMallocThreadPool::waitForThreads()

{

  for( auto& t: m_threads )

  {

    if( t.joinable() )

      t.join();

  }

}

void NoMallocThreadPool::threadProc( int threadId, const VVEncCfg& encCfg )

{

#if __linux

  if( !m_poolName.empty() )

  {

    std::string threadName( m_poolName + std::to_string( threadId ) );

    pthread_setname_np( pthread_self(), threadName.c_str() );

  }

#endif

#if ENABLE_TIME_PROFILING_MT_MODE

  ptls.reset( timeProfilerCreate( encCfg ) );

  {

    std::unique_lock< std::mutex > lock( m_nextFillSlotMutex );

    TProfiler *tp = ptls.get();

    profilers.push_back( tp );

  }

#endif

  auto nextTaskIt = m_tasks.begin();

  while( !m_exitThreads )

  {

    auto taskIt = findNextTask( threadId, nextTaskIt );

    if( !taskIt.isValid() )

    {

      std::unique_lock<std::mutex> l( m_idleMutex, std::defer_lock );

      ITT_TASKSTART( itt_domain_thrd, itt_handle_TPspinWait );

      m_waitingThreads.fetch_add( 1, std::memory_order_relaxed );

      const auto startWait = std::chrono::steady_clock::now();

      while( !m_exitThreads )

      {

        taskIt = findNextTask( threadId, nextTaskIt );

        if( taskIt.isValid() || m_exitThreads )

        {

          break;

        }

        if( !l.owns_lock()

            && m_waitingThreads.load( std::memory_order_relaxed ) > 1

            && ( BUSY_WAIT_TIME.count() == 0 || std::chrono::steady_clock::now() - startWait > BUSY_WAIT_TIME )

            && !m_exitThreads )

        {

          ITT_TASKSTART(itt_domain_thrd, itt_handle_TPblocked);

          l.lock();

          ITT_TASKEND(itt_domain_thrd, itt_handle_TPblocked);

        }

        else

        {

          std::this_thread::yield();

        }

      }

      m_waitingThreads.fetch_sub( 1, std::memory_order_relaxed );

      ITT_TASKEND( itt_domain_thrd, itt_handle_TPspinWait );

    }

    if( m_exitThreads )

    {

      return;

    }

    processTask( threadId, *taskIt );

    nextTaskIt = taskIt;

    nextTaskIt.incWrap();

  }

}

NoMallocThreadPool::TaskIterator NoMallocThreadPool::findNextTask( int threadId, TaskIterator startSearch )

{

  if( !startSearch.isValid() )

  {

    startSearch = m_tasks.begin();

  }

  bool first = true;

  for( auto it = startSearch; it != startSearch || first; it.incWrap() )

  {

#if ENABLE_VALGRIND_CODE

    MutexLock lock( m_extraMutex );

#endif

    first = false;

    Slot& t = *it;

    auto expected = WAITING;

    if( t.state.load( std::memory_order_relaxed ) == WAITING && t.state.compare_exchange_strong( expected, RUNNING ) )

    {

      if( !t.barriers.empty() )

      {

        if( std::any_of( t.barriers.cbegin(), t.barriers.cend(), []( const Barrier* b ) { return b && b->isBlocked(); } ) )

        {

          // reschedule

          t.state.store( WAITING );

          continue;

        }

        t.barriers.clear();   // clear barriers, so we don't need to check them on the next try (we assume they won't get locked again)

      }

      if( t.readyCheck && t.readyCheck( threadId, t.param ) == false )

      {

        // reschedule

        t.state.store( WAITING );

        continue;

      }

      return it;

    }

  }

  return {};

}

bool NoMallocThreadPool::processTask( int threadId, NoMallocThreadPool::Slot& task )

{

  const bool success = task.func( threadId, task.param );

#if ENABLE_VALGRIND_CODE

  MutexLock lock( m_extraMutex );

#endif

  if( !success )

  {

    task.state = WAITING;

    return false;

  }

  if( task.done != nullptr )

  {

    task.done->unlock();

  }

  if( task.counter != nullptr )

  {

    --(*task.counter);

  }

  task.state = FREE;

  return true;

}

#ifdef HAVE_PTHREADS

template<class TFunc, class... TArgs>

NoMallocThreadPool::PThread::PThread( TFunc&& func, TArgs&&... args )

{

  using WrappedCall     = std::function<void()>;

  std::unique_ptr<WrappedCall> call = std::make_unique<WrappedCall>( std::bind( func, args... ) );

  using PThreadsStartFn = void* (*) ( void* );

  PThreadsStartFn threadFn = []( void* p ) -> void*

  {

    std::unique_ptr<WrappedCall> call( static_cast<WrappedCall*>( p ) );

    ( *call )();

    return nullptr;

  };

  pthread_attr_t attr;

  int ret = pthread_attr_init( &attr );

  CHECK( ret != 0, "pthread_attr_init() failed" );

  try

  {

    size_t currStackSize = 0;

    ret = pthread_attr_getstacksize( &attr, &currStackSize );

    CHECK( ret != 0, "pthread_attr_getstacksize() failed" );

    if( currStackSize < THREAD_MIN_STACK_SIZE )

    {

      ret = pthread_attr_setstacksize( &attr, THREAD_MIN_STACK_SIZE );

      CHECK( ret != 0, "pthread_attr_setstacksize() failed" );

#  if defined( _DEBUG ) && !defined( __MINGW32__ ) && !defined( __MINGW64__ )

      ret = pthread_attr_setguardsize( &attr, 1024 * 1024 );   // set stack guard size to 1MB to more reliably deteck stack overflows

      CHECK( ret != 0, "pthread_attr_setguardsize() failed" );

#  endif

    }

    m_joinable = 0 == pthread_create( &m_id, &attr, threadFn, call.get() );

    CHECK( !m_joinable, "pthread_create() faild" );

    call.release();   // will now be freed by the thread

    pthread_attr_destroy( &attr );

  }

  catch( ... )

  {

    pthread_attr_destroy( &attr );

    throw;

  }

}

NoMallocThreadPool::PThread& NoMallocThreadPool::PThread::operator=( PThread&& other )

{

  m_id             = other.m_id;

  m_joinable       = other.m_joinable;

  other.m_id       = 0;

  other.m_joinable = false;

  return *this;

}

void NoMallocThreadPool::PThread::join()

{

  if( m_joinable )

  {

    m_joinable = false;

    pthread_join( m_id, nullptr );

  }

}

#endif   // HAVE_PTHREADS

} // namespace vvenc

//! \}