dlib C++ Library - threads_kernel_shared.cpp
// Copyright (C) 2003 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_THREADS_KERNEL_SHARED_CPp_
#define DLIB_THREADS_KERNEL_SHARED_CPp_
#include "threads_kernel_shared.h"
#include "../assert.h"
#include "../platform.h"
#include <iostream>
#ifndef DLIB_THREAD_POOL_TIMEOUT
// default to 30000 milliseconds
#define DLIB_THREAD_POOL_TIMEOUT 30000
#endif
namespace dlib
{
// ----------------------------------------------------------------------------------------
// ----------------------------------------------------------------------------------------
// threader functions
// ----------------------------------------------------------------------------------------
// ----------------------------------------------------------------------------------------
namespace threads_kernel_shared
{
bool thread_pool_has_been_destroyed = false;
// ----------------------------------------------------------------------------------------
struct threader_destruct_helper
{
// cause the thread pool to begin its destruction process when
// global objects start to be destroyed
~threader_destruct_helper()
{
thread_pool().destruct_if_ready();
}
};
// ----------------------------------------------------------------------------------------
threader& thread_pool (
)
{
static threader* thread_pool = new threader;
static threader_destruct_helper a;
return *thread_pool;
}
// ----------------------------------------------------------------------------------------
bool threader::
is_dlib_thread (
thread_id_type id
)
{
auto_mutex M(data_mutex);
return thread_ids.is_member(id);
}
// ----------------------------------------------------------------------------------------
threader::
threader (
) :
total_count(0),
function_pointer(0),
pool_count(0),
data_ready(data_mutex),
data_empty(data_mutex),
destruct(false),
destructed(data_mutex),
do_not_ever_destruct(false)
{
#ifdef WIN32
// Trying to destroy the global thread pool when we are part of a DLL and the
// DLL is being unloaded can sometimes lead to weird behavior. For example, in
// the python interpreter you will get the interpreter to hang. Or if we are
// part of a MATLAB mex file and the file is being unloaded there can also be
// similar weird issues. So when we are using dlib on windows we just disable
// the destruction of the global thread pool since it doesn't matter anyway.
// It's resources will just get freed by the OS. This is even the recommended
// thing to do by Microsoft (http://blogs.msdn.com/b/oldnewthing/archive/2012/01/05/10253268.aspx).
//
// As an aside, it's worth pointing out that the reason we try and free
// resources on program shutdown on other operating systems is so we can have
// clean reports from tools like valgrind which check for memory leaks. But
// trying to do this on windows is a lost cause so we give up in this case and
// follow the Microsoft recommendation.
do_not_ever_destruct = true;
#endif // WIN32
}
// ----------------------------------------------------------------------------------------
threader::
~threader (
)
{
data_mutex.lock();
destruct = true;
data_ready.broadcast();
// wait for all the threads to end
while (total_count > 0)
destructed.wait();
thread_pool_has_been_destroyed = true;
data_mutex.unlock();
}
// ----------------------------------------------------------------------------------------
void threader::
destruct_if_ready (
)
{
if (do_not_ever_destruct)
return;
data_mutex.lock();
// if there aren't any active threads, just maybe some sitting around
// in the pool then just destroy the threader
if (total_count == pool_count)
{
destruct = true;
data_ready.broadcast();
data_mutex.unlock();
delete this;
}
else
{
// There are still some user threads running so there isn't
// much we can really do. Just let the program end without
// cleaning up threading resources.
data_mutex.unlock();
}
}
// ----------------------------------------------------------------------------------------
void threader::
call_end_handlers (
)
{
reg.m.lock();
const thread_id_type id = get_thread_id();
thread_id_type id_copy;
member_function_pointer<> mfp;
// Remove all the member function pointers for this thread from the tree
// and call them.
while (reg.reg[id] != 0)
{
reg.reg.remove(id,id_copy,mfp);
reg.m.unlock();
mfp();
reg.m.lock();
}
reg.m.unlock();
}
// ------------------------------------------------------------------------------------
bool threader::
create_new_thread (
void (*funct)(void*),
void* param
)
{
// get a lock on the data mutex
auto_mutex M(data_mutex);
// loop to ensure that the new function pointer is in the data
while (true)
{
// if the data is empty then add new data and quit loop
if (function_pointer == 0)
{
parameter = param;
function_pointer = funct;
break;
}
else
{
// wait for data to become empty
data_empty.wait();
}
}
// get a thread for this new data
// if a new thread must be created
if (pool_count == 0)
{
// make thread and add it to the pool
if ( threads_kernel_shared_helpers::spawn_thread(thread_starter, this) == false )
{
function_pointer = 0;
parameter = 0;
data_empty.signal();
return false;
}
++total_count;
}
// wake up a thread from the pool
else
{
data_ready.signal();
}
return true;
}
// ------------------------------------------------------------------------------------
void thread_starter (
void* object
)
{
// get a reference to the calling threader object
threader& self = *static_cast<threader*>(object);
{
auto_mutex M(self.data_mutex);
// add this thread id
thread_id_type thread_id = get_thread_id();
self.thread_ids.add(thread_id);
// indicate that this thread is now in the thread pool
++self.pool_count;
while (self.destruct == false)
{
// if data is ready then process it and launch the thread
// if its not ready then go back into the pool
while (self.function_pointer != 0)
{
// indicate that this thread is now out of the thread pool
--self.pool_count;
// get the data for the function call
void (*funct)(void*) = self.function_pointer;
void* param = self.parameter;
self.function_pointer = 0;
// signal that the data is now empty
self.data_empty.signal();
self.data_mutex.unlock();
// Call funct with its intended parameter. If this function throws then
// we intentionally let the exception escape the thread and result in whatever
// happens when it gets caught by the OS (generally the program is terminated).
funct(param);
self.call_end_handlers();
self.data_mutex.lock();
// indicate that this thread is now back in the thread pool
++self.pool_count;
}
if (self.destruct == true)
break;
// if we timed out and there isn't any work to do then
// this thread will quit this loop and end.
if (self.data_ready.wait_or_timeout(DLIB_THREAD_POOL_TIMEOUT) == false &&
self.function_pointer == 0)
break;
}
// remove this thread id from thread_ids
thread_id = get_thread_id();
self.thread_ids.destroy(thread_id);
// indicate that this thread is now out of the thread pool
--self.pool_count;
--self.total_count;
self.destructed.signal();
} // end of auto_mutex M(self.data_mutex) block
}
// ------------------------------------------------------------------------------------
}
// ----------------------------------------------------------------------------------------
bool is_dlib_thread (
thread_id_type id
)
{
return threads_kernel_shared::thread_pool().is_dlib_thread(id);
}
bool is_dlib_thread (
)
{
return is_dlib_thread(get_thread_id());
}
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_THREADS_KERNEL_SHARED_CPp_