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event/DeferredMonitor: make fully thread-safe

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Instead of creating a new eventfd for each DeferredMonitor instance,
reuse EventLoop's eventfd, and add a std::list to EventLoop that
manages the list of pending DeferredMonitors.  This std::list is
protected by the same mutex as the "calls" list.

The bottom line is: reduced overhead because the per-instance eventfd
was eliminated, slightly added overhead due to Mutex usage (but
negligible), and we're thread-safe now.

This subsystem is now good enough to replace EventLoop::AddCall().
This commit is contained in:
Max Kellermann
2014-01-04 14:56:02 +01:00
parent 48c96bbaea
commit a357d84dce
4 changed files with 77 additions and 54 deletions
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43
src/event/DeferredMonitor.hxx
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@@ -23,11 +23,6 @@
#include "check.h"
#include "Compiler.h"
#ifdef USE_INTERNAL_EVENTLOOP
#include "SocketMonitor.hxx"
#include "WakeFD.hxx"
#endif
#ifdef USE_GLIB_EVENTLOOP
#include <glib.h>
#endif
@@ -39,31 +34,24 @@ class EventLoop;
/**
* Defer execution of an event into an #EventLoop.
*
* This class is thread-safe, however the constructor must be called
* from the thread that runs the #EventLoop
* This class is thread-safe.
*/
class DeferredMonitor
class DeferredMonitor {
EventLoop &loop;
#ifdef USE_INTERNAL_EVENTLOOP
: private SocketMonitor
#endif
{
#ifdef USE_INTERNAL_EVENTLOOP
std::atomic_bool pending;
WakeFD fd;
friend class EventLoop;
bool pending;
#endif
#ifdef USE_GLIB_EVENTLOOP
EventLoop &loop;
std::atomic<guint> source_id;
#endif
public:
#ifdef USE_INTERNAL_EVENTLOOP
DeferredMonitor(EventLoop &_loop)
:SocketMonitor(_loop), pending(false) {
SocketMonitor::Open(fd.Get());
SocketMonitor::Schedule(SocketMonitor::READ);
}
:loop(_loop), pending(false) {}
#endif
#ifdef USE_GLIB_EVENTLOOP
@@ -72,24 +60,11 @@ public:
#endif
~DeferredMonitor() {
#ifdef USE_INTERNAL_EVENTLOOP
/* avoid closing the WakeFD twice */
SocketMonitor::Steal();
#endif
#ifdef USE_GLIB_EVENTLOOP
Cancel();
#endif
}
EventLoop &GetEventLoop() {
#ifdef USE_INTERNAL_EVENTLOOP
return SocketMonitor::GetEventLoop();
#endif
#ifdef USE_GLIB_EVENTLOOP
return loop;
#endif
}
void Schedule();
@@ -99,10 +74,6 @@ protected:
virtual void RunDeferred() = 0;
private:
#ifdef USE_INTERNAL_EVENTLOOP
virtual bool OnSocketReady(unsigned flags) override final;
#endif
#ifdef USE_GLIB_EVENTLOOP
void Run();
static gboolean Callback(gpointer data);