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authorMax Horn2004-03-27 18:30:30 +0000
committerMax Horn2004-03-27 18:30:30 +0000
commitab64ef93ec638cd094ac8f8811ec54dd16ad2346 (patch)
treeb0cb48d58e056a9f147a6dc25aead512fccf8010
parentc33712e3d6b41442bd65e3f51c52e278a521bb08 (diff)
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clarify OSystem specification (setTimerCallback() must be 'atomic')
svn-id: r13391
-rw-r--r--common/system.h7
-rw-r--r--common/timer.cpp12
2 files changed, 9 insertions, 10 deletions
diff --git a/common/system.h b/common/system.h
index 73e89155ab..2a8d178e19 100644
--- a/common/system.h
+++ b/common/system.h
@@ -421,9 +421,14 @@ public:
* the previous one. In particular, passing a callback pointer value of 0
* is legal and can be used to clear the current timer callback.
* @see Common::Timer
+ * @note The implementation of this method must be 'atomic' in the sense
+ * that when the method returns, the previously set callback must
+ * not be in use anymore (in particular, if timers are implemented
+ * via threads, then it must be ensured that the timer thread is
+ * not using the old callback function anymore).
*
* @param callback pointer to the callback. May be 0 to reset the timer
- * @param interval the intervall (in milliseconds) between invocations
+ * @param interval the interval (in milliseconds) between invocations
* of the callback
*/
virtual void setTimerCallback(TimerProc callback, int interval) = 0;
diff --git a/common/timer.cpp b/common/timer.cpp
index 1655a2770c..f1e09a9ff0 100644
--- a/common/timer.cpp
+++ b/common/timer.cpp
@@ -51,6 +51,9 @@ Timer::Timer(OSystem *system) :
}
Timer::~Timer() {
+ // Remove the timer callback.
+ // Note: backends *must* gurantee that after this method call returns,
+ // the handler is not in use anymore; else race condtions could occurs.
_system->setTimerCallback(0, 0);
{
@@ -62,15 +65,6 @@ Timer::~Timer() {
}
}
-
- // FIXME: There is still a potential race condition here, depending on how
- // the system backend implements setTimerCallback: If timers are done using
- // threads, and if setTimerCallback does *not* gurantee that after it terminates
- // that timer thread is not run anymore, we are fine. However, if the timer
- // is still running in parallel to this destructor, then it might be that
- // it is still waiting for the _mutex. So, again depending on the backend,
- // we might end up unlocking the mutex then immediately deleting it, while
- // the timer thread is about to lock it.
_system->deleteMutex(_mutex);
}