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adding thread_group for managing async tasks

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vtnerd committed Nov 2, 2016
1 parent d51f1af commit 64094e5f4e2e909bdab0d07c3c2d16b7531d9df3
Showing with 351 additions and 100 deletions.
  1. +4 −2 src/common/CMakeLists.txt
  2. +164 −0 src/common/thread_group.cpp
  3. +133 −0 src/common/thread_group.h
  4. +50 −98 src/ringct/rctSigs.cpp
@@ -32,7 +32,8 @@ set(common_sources
dns_utils.cpp
util.cpp
i18n.cpp
perf_timer.cpp)
perf_timer.cpp
thread_group.cpp)

if (STACK_TRACE)
list(APPEND common_sources stack_trace.cpp)
@@ -55,7 +56,8 @@ set(common_private_headers
varint.h
i18n.h
perf_timer.h
stack_trace.h)
stack_trace.h
thread_group.h)

monero_private_headers(common
${common_private_headers})
@@ -0,0 +1,164 @@
// Copyright (c) 2014-2016, The Monero Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "common/thread_group.h"

#include <cassert>
#include <limits>
#include <stdexcept>

#include "common/util.h"

namespace tools
{
thread_group::thread_group(std::size_t count) : internal() {
static_assert(
std::numeric_limits<unsigned>::max() <= std::numeric_limits<std::size_t>::max(),
"unexpected truncation"
);
count = std::min<std::size_t>(count, get_max_concurrency());
count = count ? count - 1 : 0;

if (count) {
internal.emplace(count);
}
}

thread_group::data::data(std::size_t count)
: threads()
, head{nullptr}
, last(std::addressof(head))
, pending(count)
, mutex()
, has_work()
, finished_work()
, stop(false) {
threads.reserve(count);
while (count--) {
threads.push_back(std::thread(&thread_group::data::run, this));
}
}

thread_group::data::~data() noexcept {
{
const std::unique_lock<std::mutex> lock(mutex);
stop = true;
}
has_work.notify_all();
finished_work.notify_all();
for (auto& worker : threads) {
try {
worker.join();
}
catch(...) {}
}
}


void thread_group::data::sync() noexcept {
/* This function and `run()` can both throw when acquiring the lock, or in
the dispatched function. It is tough to recover from either, particularly the
lock case. These functions are marked as noexcept so that if either call
throws, the entire process is terminated. Users of the `dispatch` call are
expected to make their functions noexcept, or use std::packaged_task to copy
exceptions so that the process will continue in all but the most pessimistic
cases (std::bad_alloc). This was the existing behavior;
`asio::io_service::run` propogates errors from dispatched calls, and uncaught
exceptions on threads result in process termination. */
assert(!threads.empty());
bool not_first = false;
while (true) {
std::unique_ptr<work> next = nullptr;
{
std::unique_lock<std::mutex> lock(mutex);
pending -= std::size_t(not_first);
not_first = true;
finished_work.notify_all();

if (stop) {
return;
}

next = get_next();
if (next == nullptr) {
finished_work.wait(lock, [this] { return pending == 0 || stop; });
return;
}
}
assert(next->f);
next->f();
}
}

std::unique_ptr<thread_group::data::work> thread_group::data::get_next() noexcept {
std::unique_ptr<work> rc = std::move(head.ptr);
if (rc != nullptr) {
head.ptr = std::move(rc->next.ptr);
if (head.ptr == nullptr) {
last = std::addressof(head);
}
}
return rc;
}

void thread_group::data::run() noexcept {
// see `sync()` source for additional information
while (true) {
std::unique_ptr<work> next = nullptr;
{
std::unique_lock<std::mutex> lock(mutex);
--pending;
finished_work.notify_all();
has_work.wait(lock, [this] { return head.ptr != nullptr || stop; });
if (stop) {
return;
}
next = get_next();
}
assert(next != nullptr);
assert(next->f);
next->f();
}
}

void thread_group::data::dispatch(std::function<void()> f) {
std::unique_ptr<work> latest(new work{std::move(f), node{nullptr}});
node* const latest_node = std::addressof(latest->next);
{
const std::unique_lock<std::mutex> lock(mutex);
assert(last != nullptr);
assert(last->next == nullptr);
if (pending == std::numeric_limits<std::size_t>::max()) {
throw std::overflow_error("thread_group exceeded max queue depth");
}
last->ptr = std::move(latest);
last = latest_node;
++pending;
}
has_work.notify_one();
}
}
@@ -0,0 +1,133 @@
// Copyright (c) 2014-2016, The Monero Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include <boost/optional/optional.hpp>
#include <condition_variable>
#include <cstddef>
#include <functional>
#include <thread>
#include <utility>
#include <vector>

namespace tools
{
//! Manages zero or more threads for work dispatching
class thread_group
{
public:
//! Create `min(count, get_max_concurrency()) - 1` threads
explicit thread_group(std::size_t count);

thread_group(thread_group const&) = delete;
thread_group(thread_group&&) = delete;

//! Joins threads, but does not necessarily run all dispatched functions.
~thread_group() = default;

thread_group& operator=(thread_group const&) = delete;
thread_group& operator=(thread_group&&) = delete;

/*! Blocks until all functions provided to `dispatch` complete. Does not
destroy threads. If a dispatched function calls `this->dispatch(...)`,
`this->sync()` will continue to block until that new function completes. */
void sync() noexcept {
if (internal) {
internal->sync();
}
}

/*! Example usage:
std::unique_ptr<thread_group, thread_group::lazy_sync> sync(std::addressof(group));
which guarantees synchronization before the unique_ptr destructor returns. */
struct lazy_sync {
void operator()(thread_group* group) const noexcept {
if (group != nullptr) {
group->sync();
}
}
};

/*! `f` is invoked immediately if the thread_group is empty, otherwise
execution of `f` is queued for next available thread. If `f` is queued, any
exception leaving that function will result in process termination. Use
std::packaged_task if exceptions need to be handled. */
template<typename F>
void dispatch(F&& f) {
if (internal) {
internal->dispatch(std::forward<F>(f));
}
else {
f();
}
}

private:
class data {
public:
data(std::size_t count);
~data() noexcept;

void sync() noexcept;

void dispatch(std::function<void()> f);

private:
struct work;

struct node {
node() = delete;
std::unique_ptr<work> ptr;
};

struct work {
work() = delete;
std::function<void()> f;
node next;
};

//! Requires lock on `mutex`.
std::unique_ptr<work> get_next() noexcept;

//! Blocks until destructor is invoked, only call from thread.
void run() noexcept;

private:
std::vector<std::thread> threads;
node head;
node* last;
std::size_t pending;
std::condition_variable has_work;
std::condition_variable finished_work;
std::mutex mutex;
bool stop;
};

private:
// optionally construct elements, without separate heap allocation
boost::optional<data> internal;
};
}

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