0efb67b51e
Turns out the lock-free code using atomics was not thread-safe. The given callback could be invoked by GLib before the source_id attribute was assigned. This commit changes the DeferredMonitor class to use a Mutex to block the event loop until source_id is assigned. This bug does not exist in the 0.19 branch because it does not use the GLib main loop anymore.
102 lines
2.1 KiB
C++
102 lines
2.1 KiB
C++
/*
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* Copyright (C) 2003-2013 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef MPD_SOCKET_DEFERRED_MONITOR_HXX
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#define MPD_SOCKET_DEFERRED_MONITOR_HXX
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#include "check.h"
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#include "Compiler.h"
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#ifdef USE_EPOLL
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#include "SocketMonitor.hxx"
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#include "WakeFD.hxx"
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#else
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#include "thread/Mutex.hxx"
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#include <glib.h>
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#endif
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#include <atomic>
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class EventLoop;
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/**
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* Defer execution of an event into an #EventLoop.
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*/
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class DeferredMonitor
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#ifdef USE_EPOLL
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: private SocketMonitor
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#endif
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{
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#ifdef USE_EPOLL
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std::atomic_bool pending;
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WakeFD fd;
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#else
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EventLoop &loop;
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Mutex mutex;
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guint source_id;
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#endif
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public:
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#ifdef USE_EPOLL
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DeferredMonitor(EventLoop &_loop)
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:SocketMonitor(_loop), pending(false) {
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SocketMonitor::Open(fd.Get());
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SocketMonitor::Schedule(SocketMonitor::READ);
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}
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#else
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DeferredMonitor(EventLoop &_loop)
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:loop(_loop), source_id(0) {}
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#endif
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~DeferredMonitor() {
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#ifdef USE_EPOLL
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/* avoid closing the WakeFD twice */
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SocketMonitor::Steal();
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#else
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Cancel();
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#endif
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}
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EventLoop &GetEventLoop() {
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#ifdef USE_EPOLL
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return SocketMonitor::GetEventLoop();
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#else
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return loop;
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#endif
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}
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void Schedule();
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void Cancel();
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protected:
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virtual void RunDeferred() = 0;
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private:
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#ifdef USE_EPOLL
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virtual bool OnSocketReady(unsigned flags) override final;
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#else
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void Run();
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static gboolean Callback(gpointer data);
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#endif
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};
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#endif /* MAIN_NOTIFY_H */
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