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#include "thread-pool.hh"
#include "affinity.hh"
namespace nix {
ThreadPool::ThreadPool(size_t _maxThreads)
: maxThreads(_maxThreads)
{
restoreAffinity(); // FIXME
if (!maxThreads) {
maxThreads = std::thread::hardware_concurrency();
if (!maxThreads) maxThreads = 1;
}
debug(format("starting pool of %d threads") % maxThreads);
}
ThreadPool::~ThreadPool()
{
std::vector<std::thread> workers;
{
auto state(state_.lock());
state->quit = true;
std::swap(workers, state->workers);
}
debug(format("reaping %d worker threads") % workers.size());
work.notify_all();
for (auto & thr : workers)
thr.join();
}
void ThreadPool::enqueue(const work_t & t)
{
auto state(state_.lock());
if (state->quit)
throw ThreadPoolShutDown("cannot enqueue a work item while the thread pool is shutting down");
state->left.push(t);
if (state->left.size() > state->workers.size() && state->workers.size() < maxThreads)
state->workers.emplace_back(&ThreadPool::workerEntry, this);
work.notify_one();
}
void ThreadPool::process()
{
/* Loop until there are no active work items *and* there either
are no queued items or there is an exception. The
post-condition is that no new items will become active. */
while (true) {
auto state(state_.lock());
if (!state->active) {
if (state->exception)
std::rethrow_exception(state->exception);
if (state->left.empty())
break;
}
state.wait(done);
}
}
void ThreadPool::workerEntry()
{
bool didWork = false;
std::exception_ptr exc;
while (true) {
work_t w;
{
auto state(state_.lock());
if (didWork) {
assert(state->active);
state->active--;
if (exc) {
if (!state->exception) {
state->exception = exc;
// Tell the other workers to quit.
state->quit = true;
work.notify_all();
} else {
/* Print the exception, since we can't
propagate it. */
try {
std::rethrow_exception(exc);
} catch (std::exception & e) {
if (!dynamic_cast<Interrupted*>(&e) &&
!dynamic_cast<ThreadPoolShutDown*>(&e))
ignoreException();
} catch (...) {
}
}
}
}
/* Wait until a work item is available or another thread
had an exception or we're asked to quit. */
while (true) {
if (state->quit) {
if (!state->active)
done.notify_one();
return;
}
if (!state->left.empty()) break;
if (!state->active) {
done.notify_one();
return;
}
state.wait(work);
}
w = std::move(state->left.front());
state->left.pop();
state->active++;
}
try {
w();
} catch (...) {
exc = std::current_exception();
}
didWork = true;
}
}
}
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