mirror of
https://github.com/matrix-construct/construct
synced 2024-08-25 19:12:08 +02:00
193 lines
3.9 KiB
C++
193 lines
3.9 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2019 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#include "ctx.h"
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namespace ircd::ctx::ole
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{
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extern conf::item<size_t> thread_max;
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std::mutex mutex;
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std::condition_variable cond;
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std::deque<offload::function> queue;
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std::vector<std::thread> threads;
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bool termination;
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static offload::function pop();
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static void push(offload::function &&);
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static void worker() noexcept;
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}
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decltype(ircd::ctx::ole::thread_max)
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ircd::ctx::ole::thread_max
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{
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{ "name", "ircd.ctx.ole.thread.max" },
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{ "default", int64_t(1) },
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};
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ircd::ctx::ole::init::init()
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{
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assert(threads.empty());
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termination = false;
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}
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ircd::ctx::ole::init::~init()
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noexcept
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{
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std::unique_lock lock
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{
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mutex
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};
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termination = true;
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cond.notify_all();
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cond.wait(lock, []
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{
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return threads.empty();
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});
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}
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ircd::ctx::ole::offload::offload(const function &func)
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:offload{opts{}, func}
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{
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}
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ircd::ctx::ole::offload::offload(const opts &opts,
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const function &func)
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{
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assert(current);
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assert(opts.concurrency == 1); // not yet implemented
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// Prepare the offload package on our stack here. These objects will
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// remain here for the duration of the offload.
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latch latch{1};
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std::exception_ptr eptr;
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auto *const context(current);
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auto closure{[&func, &latch, &eptr, &context]
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() noexcept
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{
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try
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{
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func();
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}
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catch(...)
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{
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// Note that the write to eptr is taking place on a different
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// thread from where we created the eptr.
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eptr = std::current_exception();
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}
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// The ctx::signal() is a special device which executes the closure
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// as soon as the target context is not currently running on any
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// thread. This has the ability to provide the cross-thread
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// synchronization we need to hit the latch from this thread.
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assert(context);
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signal(*context, [&latch]
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{
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assert(!latch.is_ready());
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latch.count_down();
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});
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}};
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// interrupt(ctx) is suppressed while this context has offloaded some work
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// to another thread. This context must stay right here and not disappear
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// until the other thread signals back. Note that the destructor is
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// capable of throwing an interrupt that was received during this scope.
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const uninterruptible uninterruptible;
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ole::push(std::move(closure)); // scope address required for clang-7
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latch.wait();
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// Don't throw any exception if there is a pending interrupt for this ctx.
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// Two exceptions will be thrown in that case and if there's an interrupt
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// we don't care about eptr anyway.
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if(likely(!interruption_requested()))
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if(unlikely(eptr))
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std::rethrow_exception(eptr);
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}
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void
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ircd::ctx::ole::push(offload::function &&func)
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{
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if(unlikely(threads.size() < size_t(thread_max)))
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threads.emplace_back(&worker);
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const std::lock_guard lock
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{
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mutex
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};
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queue.emplace_back(std::move(func));
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cond.notify_all();
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}
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void
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ircd::ctx::ole::worker()
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noexcept try
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{
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while(1)
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{
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const auto func
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{
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pop()
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};
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func();
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}
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}
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catch(const interrupted &)
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{
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const std::lock_guard lock
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{
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mutex
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};
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const auto it
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{
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std::find_if(begin(threads), end(threads), []
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(const auto &thread)
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{
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return thread.get_id() == std::this_thread::get_id();
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})
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};
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assert(it != end(threads));
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auto &this_thread(*it);
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this_thread.detach();
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threads.erase(it);
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cond.notify_all();
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}
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ircd::ctx::ole::offload::function
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ircd::ctx::ole::pop()
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{
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std::unique_lock lock
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{
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mutex
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};
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cond.wait(lock, []
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{
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if(!queue.empty())
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return true;
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if(unlikely(termination))
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throw interrupted{};
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return false;
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});
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auto function
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{
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std::move(queue.front())
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};
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queue.pop_front();
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return function;
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}
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