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// OpenVPN -- An application to securely tunnel IP networks
// over a single port, with support for SSL/TLS-based
// session authentication and key exchange,
// packet encryption, packet authentication, and
// packet compression.
//
// Copyright (C) 2012-2022 OpenVPN Inc.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License Version 3
// as published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program in the COPYING file.
// If not, see <http://www.gnu.org/licenses/>.
#ifndef OPENVPN_COMMON_PTHREADCOND_H
#define OPENVPN_COMMON_PTHREADCOND_H
#include <mutex>
#include <condition_variable>
#include <chrono>
#include <openvpn/common/stop.hpp>
namespace openvpn {
// Barrier class that is useful in cases where all threads
// need to reach a known point before executing some action.
// Note that this barrier implementation is
// constructed using C++11 condition variables.
class PThreadBarrier
{
enum State
{
UNSIGNALED = 0, // initial state
SIGNALED, // signal() was called
ERROR_THROWN, // error() was called
};
public:
// status return from wait()
enum Status
{
SUCCESS = 0, // successful
CHOSEN_ONE, // successful and chosen (only one thread is chosen)
TIMEOUT, // timeout
ERROR_SIGNAL, // at least one thread called error()
};
PThreadBarrier(const int initial_limit = -1)
: stop(nullptr),
limit(initial_limit)
{
}
PThreadBarrier(Stop *stop_arg, const int initial_limit = -1)
: stop(stop_arg),
limit(initial_limit)
{
}
// All callers will increment count and block until
// count == limit. CHOSEN_ONE will be returned to
// the first caller to reach limit. This caller can
// then release all the other callers by calling
// signal().
int wait(const unsigned int seconds)
{
// allow asynchronous stop
Stop::Scope stop_scope(stop, [this]()
{ error(); });
bool timeout = false;
int ret;
std::unique_lock<std::mutex> lock(mutex);
const unsigned int c = ++count;
while (state == UNSIGNALED
&& (limit < 0 || c < static_cast<unsigned int>(limit))
&& !timeout)
timeout = (cv.wait_for(lock, std::chrono::seconds(seconds)) == std::cv_status::timeout);
if (timeout)
ret = TIMEOUT;
else if (state == ERROR_THROWN)
ret = ERROR_SIGNAL;
else if (state == UNSIGNALED && !chosen)
{
ret = CHOSEN_ONE;
chosen = true;
}
else
ret = SUCCESS;
return ret;
}
void set_limit(const int new_limit)
{
std::unique_lock<std::mutex> lock(mutex);
limit = new_limit;
cv.notify_all();
}
// Generally, only the CHOSEN_ONE calls signal() after its work
// is complete, to allow the other threads to pass the barrier.
void signal()
{
signal_(SIGNALED);
}
// Causes all threads waiting on wait() (and those which call wait()
// in the future) to exit with ERROR_SIGNAL status.
void error()
{
signal_(ERROR_THROWN);
}
private:
void signal_(const State newstate)
{
std::unique_lock<std::mutex> lock(mutex);
if (state == UNSIGNALED)
{
state = newstate;
cv.notify_all();
}
}
std::mutex mutex;
std::condition_variable cv;
Stop *stop;
State state{UNSIGNALED};
bool chosen = false;
int count = 0;
int limit;
};
} // namespace openvpn
#endif
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