208 lines
3.6 KiB
C++
208 lines
3.6 KiB
C++
// SPDX-License-Identifier: GPL-2.0-or-later
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// Copyright The Music Player Daemon Project
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#include "SignalMonitor.hxx"
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#include "event/Features.h"
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#ifndef _WIN32
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#include "SocketEvent.hxx"
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#include "util/Manual.hxx"
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#include "system/Error.hxx"
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#ifdef USE_SIGNALFD
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#include "system/SignalFD.hxx"
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#else
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#include "WakeFD.hxx"
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#endif
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#ifndef USE_SIGNALFD
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#include <atomic>
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#endif
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#include <algorithm>
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#include <array>
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#include <cassert>
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#include <csignal>
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#ifdef USE_SIGNALFD
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#include <pthread.h>
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#endif
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class SignalMonitor final {
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#ifdef USE_SIGNALFD
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SignalFD fd;
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#else
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WakeFD fd;
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#endif
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SocketEvent event;
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public:
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explicit SignalMonitor(EventLoop &_loop)
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:event(_loop, BIND_THIS_METHOD(OnSocketReady)) {
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#ifndef USE_SIGNALFD
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event.Open(fd.GetSocket());
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event.ScheduleRead();
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#endif
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}
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[[nodiscard]] auto &GetEventLoop() const noexcept {
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return event.GetEventLoop();
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}
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#ifdef USE_SIGNALFD
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void Update(sigset_t &mask) noexcept {
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const bool was_open = event.IsDefined();
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fd.Create(mask);
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if (!was_open) {
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event.Open(SocketDescriptor(fd.Get()));
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event.ScheduleRead();
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}
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}
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#else
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void WakeUp() noexcept {
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fd.Write();
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}
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#endif
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private:
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void OnSocketReady(unsigned flags) noexcept;
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};
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/* this should be enough - is it? */
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static constexpr unsigned MAX_SIGNAL = 64;
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static std::array<SignalHandler, MAX_SIGNAL> signal_handlers;
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#ifdef USE_SIGNALFD
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static sigset_t signal_mask;
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#else
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static std::array<std::atomic_bool, MAX_SIGNAL> signal_pending;
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#endif
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static Manual<SignalMonitor> monitor;
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#ifdef USE_SIGNALFD
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/**
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* This is a pthread_atfork() callback that unblocks the signals that
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* were blocked for our signalfd(). Without this, our child processes
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* would inherit the blocked signals.
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*/
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static void
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at_fork_child() noexcept
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{
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sigprocmask(SIG_UNBLOCK, &signal_mask, nullptr);
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}
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#else
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static void
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SignalCallback(int signo) noexcept
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{
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assert(signal_handlers[signo]);
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if (!signal_pending[signo].exchange(true))
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monitor->WakeUp();
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}
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#endif
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void
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SignalMonitorInit(EventLoop &loop)
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{
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#ifdef USE_SIGNALFD
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sigemptyset(&signal_mask);
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pthread_atfork(nullptr, nullptr, at_fork_child);
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#endif
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monitor.Construct(loop);
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}
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#ifndef USE_SIGNALFD
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static void
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x_sigaction(int signum, const struct sigaction &act)
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{
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if (sigaction(signum, &act, nullptr) < 0)
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throw MakeErrno("sigaction() failed");
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}
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#endif
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void
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SignalMonitorFinish() noexcept
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{
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#ifdef USE_SIGNALFD
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signal_handlers = {};
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#else
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struct sigaction sa;
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sa.sa_flags = 0;
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sigemptyset(&sa.sa_mask);
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sa.sa_handler = SIG_DFL;
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for (unsigned i = 0; i < MAX_SIGNAL; ++i) {
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if (signal_handlers[i]) {
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sigaction(i, &sa, nullptr);
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signal_handlers[i] = nullptr;
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}
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}
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std::fill(signal_pending.begin(), signal_pending.end(), false);
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#endif
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monitor.Destruct();
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}
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void
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SignalMonitorRegister(int signo, SignalHandler handler)
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{
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assert(!signal_handlers[signo]);
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#ifndef USE_SIGNALFD
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assert(!signal_pending[signo]);
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#endif
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signal_handlers[signo] = handler;
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#ifdef USE_SIGNALFD
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sigaddset(&signal_mask, signo);
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if (sigprocmask(SIG_BLOCK, &signal_mask, nullptr) < 0)
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throw MakeErrno("sigprocmask() failed");
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monitor->Update(signal_mask);
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#else
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struct sigaction sa;
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sa.sa_flags = 0;
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sigemptyset(&sa.sa_mask);
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sa.sa_handler = SignalCallback;
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x_sigaction(signo, sa);
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#endif
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}
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void
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SignalMonitor::OnSocketReady(unsigned) noexcept
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{
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#ifdef USE_SIGNALFD
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int signo;
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while ((signo = fd.Read()) >= 0) {
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assert(unsigned(signo) < MAX_SIGNAL);
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assert(signal_handlers[signo]);
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signal_handlers[signo]();
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}
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#else
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fd.Read();
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for (unsigned i = 0; i < MAX_SIGNAL; ++i)
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if (signal_pending[i].exchange(false))
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signal_handlers[i]();
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#endif
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}
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#endif
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