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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <shutdown.h>
#include <logging.h>
#include <util/tokenpipe.h>
#include <config/bitcoin-config.h>
#include <assert.h>
#include <atomic>
#ifdef WIN32
#include <condition_variable>
#endif
static std::atomic<bool> fRequestShutdown(false);
#ifdef WIN32
/** On windows it is possible to simply use a condition variable. */
std::mutex g_shutdown_mutex;
std::condition_variable g_shutdown_cv;
#else
/** On UNIX-like operating systems use the self-pipe trick.
*/
static TokenPipeEnd g_shutdown_r;
static TokenPipeEnd g_shutdown_w;
#endif
bool InitShutdownState()
{
#ifndef WIN32
std::optional<TokenPipe> pipe = TokenPipe::Make();
if (!pipe) return false;
g_shutdown_r = pipe->TakeReadEnd();
g_shutdown_w = pipe->TakeWriteEnd();
#endif
return true;
}
void StartShutdown()
{
#ifdef WIN32
std::unique_lock<std::mutex> lk(g_shutdown_mutex);
fRequestShutdown = true;
g_shutdown_cv.notify_one();
#else
// This must be reentrant and safe for calling in a signal handler, so using a condition variable is not safe.
// Make sure that the token is only written once even if multiple threads call this concurrently or in
// case of a reentrant signal.
if (!fRequestShutdown.exchange(true)) {
// Write an arbitrary byte to the write end of the shutdown pipe.
int res = g_shutdown_w.TokenWrite('x');
if (res != 0) {
LogPrintf("Sending shutdown token failed\n");
assert(0);
}
}
#endif
}
void AbortShutdown()
{
if (fRequestShutdown) {
// Cancel existing shutdown by waiting for it, this will reset condition flags and remove
// the shutdown token from the pipe.
WaitForShutdown();
}
fRequestShutdown = false;
}
bool ShutdownRequested()
{
return fRequestShutdown;
}
void WaitForShutdown()
{
#ifdef WIN32
std::unique_lock<std::mutex> lk(g_shutdown_mutex);
g_shutdown_cv.wait(lk, [] { return fRequestShutdown.load(); });
#else
int res = g_shutdown_r.TokenRead();
if (res != 'x') {
LogPrintf("Reading shutdown token failed\n");
assert(0);
}
#endif
}
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