Using Monitor class directly is more complex but we win in performance. Using lock statement is the easiest way to go but not very performant under unexpected situations.
Suspend itimer while in handler c how to#
There are few ways how to avoid it and here were three of these shown. Overlapping timer callbacks may cause a lot of trouble in system. Before using this method be sure that it fits your scenario and running timer exactly after given interval is not hard requirement. We let it wait ten seconds before going to next round and its interval will also be ten seconds. I there was successfully acquired lock then we have to activate timer again.
Suspend itimer while in handler c code#
When code in try block is executed then call in finally block is called. The code above stops timer before work is made in callback. _timer.Change(TimerInterval, TimerInterval) _timer.Change( Timeout.Infinite, Timeout.Infinite) _timer = new Timer(Callback, null, 0, TimerInterval) Private const long TimerInterval = 10000 For this we change timer start time and interval to Timeout.Infinite. We can get rid of those “empty” calls introduced in previous point by stopping timer while callback is running. This method is also good for cases when some work in timer callback must be done at every call and there’s also some work that can’t be done in parallel by multiple threads. Calls to timer callback still happen but they quit fast when failing to acquire lock. Now we almost got rid of overlapping calls but not completely. To get better idea how things work internally, please read my blog post Are lock and Monitor the same in C#? The sample below uses Monitor.TryEnter() instead of Monitor.Enter() to acquire lock. Lock in C# is actually syntactic sugar that transforms to try-finally block that hosts Monitor class. To avoid callback calls forming a long waiting row we can use Monitor class to jump out from calls that failed to acquire lock.
As soon as lock is released the next call that successfully acquires lock starts executing lock body. There are no overlapping calls anymore but there is still one problem – if callback takes minute to execute for some unexpected reason then there will be six calls waiting after lock. _timer = new Timer(Callback, null, 3000, 2000) Private static object _locker = new object() If we want to avoid overlapping then first and simplest idea to come out with is locking the part of callback body where actual work is done. If callback is not finished after ten seconds then next next call to it is made by timer in parallel. We have no controls for overlapping calls here. _timer = new Timer(Callback, null, 0, 10000) Let’s start with simple class that hosts timer that fires callback after every ten seconds.
This post introduces some options to avoid overlapping timer calls. It may also end up by making unexpected parallel data processing that distorts the results. It may end up with loading some external system too much. With real scenarios we can easily face situations where timer calls its callback again but previous call is not finished yet. With timers we can execute code with specified interval. You don't need to do anything with it in your handler.Timers are useful. Just set it_interval to zero, and you'll get a one-shot timer. I tried to set the setitimer interval to 0, but I am not sure how to use the same timer within the TimerStop signal handler function Printf("Timer ran out! Stopping timer\n") If (setitimer(ITIMER_REAL, &it_val, NULL) = -1) set interval timer, returns SIGALRM on expiration
If (signal(SIGALRM, TimerStop) = SIG_ERR) #define INTERVAL 2 // number of seconds to go off I want StopTimer to handle the signal to stop the timer #include I am trying to have a signal handler stop a timer without exiting my program.
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