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authorMax Kellermann <max@duempel.org>2013-01-10 00:57:18 +0100
committerMax Kellermann <max@duempel.org>2013-01-10 00:57:18 +0100
commit5c3c5066382a22b1bf19ebbcc320e222b6812bfb (patch)
tree482eb1db3aba5df012ea598db39a346993644360 /src/GlobalEvents.cxx
parentecd5eb02c5094d3160db9d92937f7011e172c254 (diff)
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GlobalEvents: lock-less operation using std::atomic
Use a bit field instead of a mutex-protected bool array.
Diffstat (limited to 'src/GlobalEvents.cxx')
-rw-r--r--src/GlobalEvents.cxx39
1 files changed, 8 insertions, 31 deletions
diff --git a/src/GlobalEvents.cxx b/src/GlobalEvents.cxx
index a483e31b4..664803ca3 100644
--- a/src/GlobalEvents.cxx
+++ b/src/GlobalEvents.cxx
@@ -20,9 +20,10 @@
#include "config.h"
#include "GlobalEvents.hxx"
#include "event/WakeFD.hxx"
-#include "thread/Mutex.hxx"
#include "mpd_error.h"
+#include <atomic>
+
#include <assert.h>
#include <glib.h>
#include <string.h>
@@ -34,8 +35,7 @@
namespace GlobalEvents {
static WakeFD wake_fd;
static guint source_id;
- static Mutex mutex;
- static bool flags[MAX];
+ static std::atomic_uint flags;
static Handler handlers[MAX];
}
@@ -59,15 +59,10 @@ GlobalEventCallback(G_GNUC_UNUSED GIOChannel *source,
if (!GlobalEvents::wake_fd.Read())
return true;
- bool events[GlobalEvents::MAX];
- GlobalEvents::mutex.lock();
- memcpy(events, GlobalEvents::flags, sizeof(events));
- memset(GlobalEvents::flags, 0,
- sizeof(GlobalEvents::flags));
- GlobalEvents::mutex.unlock();
+ const unsigned flags = GlobalEvents::flags.fetch_and(0);
for (unsigned i = 0; i < GlobalEvents::MAX; ++i)
- if (events[i])
+ if (flags & (1u << i))
/* invoke the event handler */
InvokeGlobalEvent(GlobalEvents::Event(i));
@@ -113,25 +108,7 @@ GlobalEvents::Emit(Event event)
{
assert((unsigned)event < MAX);
- mutex.lock();
- if (flags[event]) {
- /* already set: don't write */
- mutex.unlock();
- return;
- }
-
- flags[event] = true;
- mutex.unlock();
-
- wake_fd.Write();
-}
-
-void
-GlobalEvents::FastEmit(Event event)
-{
- assert((unsigned)event < MAX);
-
- flags[event] = true;
-
- wake_fd.Write();
+ const unsigned mask = 1u << unsigned(event);
+ if ((GlobalEvents::flags.fetch_or(mask) & mask) == 0)
+ wake_fd.Write();
}