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1d92d89edb
Replace exceptions thrown by signal and wait methods with [[nodiscard]] return values. This is mostly a refactoring, but there is a slight change of behavior if AbortShutdown function fails. The original behavior which was unintentionally changed in #27861 is restored, so it now triggers an assert failure again instead of throwing an exception. (The AbortShutdown function is only ever called in the the GUI version of Bitcoin Core when corruption is detected on loading and the user tries to reindex.) Problems with using exceptions were pointed out by MarcoFalke in https://github.com/bitcoin/bitcoin/pull/27861#discussion_r1255496707.
77 lines
1.8 KiB
C++
77 lines
1.8 KiB
C++
// Copyright (c) 2022 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#include <util/signalinterrupt.h>
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#ifdef WIN32
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#include <mutex>
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#else
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#include <util/tokenpipe.h>
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#endif
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#include <ios>
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#include <optional>
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namespace util {
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SignalInterrupt::SignalInterrupt() : m_flag{false}
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{
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#ifndef WIN32
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std::optional<TokenPipe> pipe = TokenPipe::Make();
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if (!pipe) throw std::ios_base::failure("Could not create TokenPipe");
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m_pipe_r = pipe->TakeReadEnd();
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m_pipe_w = pipe->TakeWriteEnd();
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#endif
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}
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SignalInterrupt::operator bool() const
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{
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return m_flag;
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}
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bool SignalInterrupt::reset()
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{
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// Cancel existing interrupt by waiting for it, this will reset condition flags and remove
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// the token from the pipe.
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if (*this && !wait()) return false;
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m_flag = false;
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return true;
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}
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bool SignalInterrupt::operator()()
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{
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#ifdef WIN32
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std::unique_lock<std::mutex> lk(m_mutex);
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m_flag = true;
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m_cv.notify_one();
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#else
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// This must be reentrant and safe for calling in a signal handler, so using a condition variable is not safe.
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// Make sure that the token is only written once even if multiple threads call this concurrently or in
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// case of a reentrant signal.
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if (!m_flag.exchange(true)) {
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// Write an arbitrary byte to the write end of the pipe.
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int res = m_pipe_w.TokenWrite('x');
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if (res != 0) {
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return false;
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}
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}
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#endif
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return true;
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}
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bool SignalInterrupt::wait()
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{
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#ifdef WIN32
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std::unique_lock<std::mutex> lk(m_mutex);
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m_cv.wait(lk, [this] { return m_flag.load(); });
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#else
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int res = m_pipe_r.TokenRead();
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if (res != 'x') {
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return false;
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}
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#endif
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return true;
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}
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} // namespace util
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