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/*
* Copyright 2003-2018 The Music Player Daemon Project
* http://www.musicpd.org
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "SignalMonitor.hxx"
#include "config.h"
#ifndef _WIN32
#include "SocketMonitor.hxx"
#include "util/Manual.hxx"
#include "system/Error.hxx"
#ifdef USE_SIGNALFD
#include "system/SignalFD.hxx"
#else
#include "WakeFD.hxx"
#endif
#ifndef USE_SIGNALFD
#include <atomic>
#endif
#include <algorithm>
#ifdef USE_SIGNALFD
#include <pthread.h>
#endif
#include <assert.h>
#include <signal.h>
class SignalMonitor final : private SocketMonitor {
#ifdef USE_SIGNALFD
SignalFD fd;
#else
WakeFD fd;
#endif
public:
SignalMonitor(EventLoop &_loop)
:SocketMonitor(_loop) {
#ifndef USE_SIGNALFD
SocketMonitor::Open(SocketDescriptor(fd.Get()));
SocketMonitor::ScheduleRead();
#endif
}
using SocketMonitor::GetEventLoop;
#ifdef USE_SIGNALFD
void Update(sigset_t &mask) noexcept {
const bool was_open = SocketMonitor::IsDefined();
fd.Create(mask);
if (!was_open) {
SocketMonitor::Open(SocketDescriptor(fd.Get()));
SocketMonitor::ScheduleRead();
}
}
#else
void WakeUp() noexcept {
fd.Write();
}
#endif
private:
bool OnSocketReady(unsigned flags) noexcept override;
};
/* this should be enough - is it? */
static constexpr unsigned MAX_SIGNAL = 64;
static SignalHandler signal_handlers[MAX_SIGNAL];
#ifdef USE_SIGNALFD
static sigset_t signal_mask;
#else
static std::atomic_bool signal_pending[MAX_SIGNAL];
#endif
static Manual<SignalMonitor> monitor;
#ifdef USE_SIGNALFD
/**
* This is a pthread_atfork() callback that unblocks the signals that
* were blocked for our signalfd(). Without this, our child processes
* would inherit the blocked signals.
*/
static void
at_fork_child() noexcept
{
sigprocmask(SIG_UNBLOCK, &signal_mask, nullptr);
}
#else
static void
SignalCallback(int signo) noexcept
{
assert(signal_handlers[signo]);
if (!signal_pending[signo].exchange(true))
monitor->WakeUp();
}
#endif
void
SignalMonitorInit(EventLoop &loop)
{
#ifdef USE_SIGNALFD
sigemptyset(&signal_mask);
pthread_atfork(nullptr, nullptr, at_fork_child);
#endif
monitor.Construct(loop);
}
#ifndef USE_SIGNALFD
static void
x_sigaction(int signum, const struct sigaction &act)
{
if (sigaction(signum, &act, nullptr) < 0)
throw MakeErrno("sigaction() failed");
}
#endif
void
SignalMonitorFinish() noexcept
{
#ifdef USE_SIGNALFD
std::fill_n(signal_handlers, MAX_SIGNAL, nullptr);
#else
struct sigaction sa;
sa.sa_flags = 0;
sigemptyset(&sa.sa_mask);
sa.sa_handler = SIG_DFL;
for (unsigned i = 0; i < MAX_SIGNAL; ++i) {
if (signal_handlers[i]) {
sigaction(i, &sa, nullptr);
signal_handlers[i] = nullptr;
}
}
std::fill_n(signal_pending, MAX_SIGNAL, false);
#endif
monitor.Destruct();
}
void
SignalMonitorRegister(int signo, SignalHandler handler)
{
assert(!signal_handlers[signo]);
#ifndef USE_SIGNALFD
assert(!signal_pending[signo]);
#endif
signal_handlers[signo] = handler;
#ifdef USE_SIGNALFD
sigaddset(&signal_mask, signo);
if (sigprocmask(SIG_BLOCK, &signal_mask, nullptr) < 0)
throw MakeErrno("sigprocmask() failed");
monitor->Update(signal_mask);
#else
struct sigaction sa;
sa.sa_flags = 0;
sigemptyset(&sa.sa_mask);
sa.sa_handler = SignalCallback;
x_sigaction(signo, sa);
#endif
}
bool
SignalMonitor::OnSocketReady(unsigned) noexcept
{
#ifdef USE_SIGNALFD
int signo;
while ((signo = fd.Read()) >= 0) {
assert(unsigned(signo) < MAX_SIGNAL);
assert(signal_handlers[signo]);
signal_handlers[signo]();
}
#else
fd.Read();
for (unsigned i = 0; i < MAX_SIGNAL; ++i)
if (signal_pending[i].exchange(false))
signal_handlers[i]();
#endif
return true;
}
#endif
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