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Making crossplat::threadpool::shared_instance() safe to use in cpprest DLL #611

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Merged
merged 4 commits into from
Jan 24, 2018
Merged

Making crossplat::threadpool::shared_instance() safe to use in cpprest DLL #611

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f250c4c
When the C++ REST SDK is built as a DLL on Windows, and unloaded befo…
garethsb Nov 24, 2017
01d5c19
Take 2. We can't just use TerminateThread indiscriminately because th…
garethsb Nov 27, 2017
9da20ab
Export the shared instance to allow cross-platform implementation of …
garethsb Dec 15, 2017
e7566e2
Use improved shutdown logic even when building as static lib, because…
ras0219-msft Jan 24, 2018
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2 changes: 1 addition & 1 deletion Release/include/pplx/threadpool.h
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Original file line number Diff line number Diff line change
Expand Up @@ -52,7 +52,7 @@ using java_local_ref = std::unique_ptr<typename std::remove_pointer<T>::type, ja
class threadpool
{
public:
static threadpool& shared_instance();
_ASYNCRTIMP static threadpool& shared_instance();
_ASYNCRTIMP static std::unique_ptr<threadpool> __cdecl construct(size_t num_threads);

virtual ~threadpool() = default;
Expand Down
65 changes: 34 additions & 31 deletions Release/src/pplx/threadpool.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,16 +9,7 @@
#if !defined(CPPREST_EXCLUDE_WEBSOCKETS) || !defined(_WIN32)
#include "pplx/threadpool.h"

#if !defined(_WIN32)
#define CPPREST_PTHREADS
#endif

#if defined(CPPREST_PTHREADS)
#include <pthread.h>
#else
#include <thread>
#endif

#include <boost/asio/detail/thread.hpp>
#include <vector>

#if defined(__ANDROID__)
Expand All @@ -44,27 +35,14 @@ struct threadpool_impl final : crossplat::threadpool
m_service.stop();
for (auto iter = m_threads.begin(); iter != m_threads.end(); ++iter)
{
#if defined(CPPREST_PTHREADS)
pthread_t t = *iter;
void* res;
pthread_join(t, &res);
#else
iter->join();
#endif
(*iter)->join();
}
}

private:
void add_thread()
{
#ifdef CPPREST_PTHREADS
pthread_t t;
auto result = pthread_create(&t, nullptr, &thread_start, this);
if (result == 0)
m_threads.push_back(t);
#else
m_threads.push_back(std::thread(&thread_start, this));
#endif
m_threads.push_back(std::unique_ptr<boost::asio::detail::thread>(new boost::asio::detail::thread([&]{ thread_start(this); })));
}

#if defined(__ANDROID__)
Expand All @@ -89,11 +67,7 @@ struct threadpool_impl final : crossplat::threadpool
return arg;
}

#if defined(CPPREST_PTHREADS)
std::vector<pthread_t> m_threads;
#else
std::vector<std::thread> m_threads;
#endif
std::vector<std::unique_ptr<boost::asio::detail::thread>> m_threads;
boost::asio::io_service::work m_work;
};
}
Expand Down Expand Up @@ -133,6 +107,35 @@ threadpool& threadpool::shared_instance()
return s_shared;
}

#elif defined(_WIN32)

// if linked into a DLL, the threadpool shared instance will be destroyed at DLL_PROCESS_DETACH,
// at which stage joining threads causes deadlock, hence this dance
threadpool& threadpool::shared_instance()
{
static bool terminate_threads = false;
static struct restore_terminate_threads
{
~restore_terminate_threads()
{
boost::asio::detail::thread::set_terminate_threads(terminate_threads);
}
} destroyed_after;

static threadpool_impl s_shared(40);

static struct enforce_terminate_threads
{
~enforce_terminate_threads()
{
terminate_threads = boost::asio::detail::thread::terminate_threads();
boost::asio::detail::thread::set_terminate_threads(true);
}
} destroyed_before;

return s_shared;
}

#else

// initialize the static shared threadpool
Expand All @@ -156,4 +159,4 @@ std::unique_ptr<crossplat::threadpool> crossplat::threadpool::construct(size_t n
{
return std::unique_ptr<crossplat::threadpool>(new threadpool_impl(num_threads));
}
#endif
#endif