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PO"Atomically" changing a System.Threading.Timer
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copied!<p>Let's say I have an existing System.Threading.Timer instance and I'd like to call Change on it to push it's firing time back:</p> <pre><code>var timer = new Timer(DelayCallback, null, 10000, Timeout.Infinite); // ... (sometime later but before DelayCallback has executed) timer.Change(20000, Timeout.Infinite); </code></pre> <p>I'm using this timer to perform an "idle callback" after a period of no activity. ("Idle" and "no activity" are application-defined conditions in this case...the specifics aren't terribly important.) Every time I perform an "action", I want to reset the timer so that it is always set to fire 10 seconds after that.</p> <p>However, there is an inherent race condition because when I call Change, I can't tell if the Timer has already fired based on its old settings. (I can, of course, tell if my callback has happened but I can't tell if the CLR's internal timer thread has queued my callback to the threadpool and its execution is imminent.)</p> <p>Now I know I can call Dispose on the timer instance and re-create it each time I need to "push it back". but this <em>seems</em> less efficient than just changing the existing timer. Of course it <em>may</em> not be...I'll run some micro-benchmarks in a bit and let you all know.</p> <p>Alternatively, I can always keep track of the expected firing time (via DateTime.Now.AddSeconds(10)) and, if the original Timer fires, ignore it by checking DateTime.Now in the callback. (I have a nagging concern that this may not be 100% reliable on account of the Timer using TimeSpan and my check using DateTime...this may not be an issue but I'm not completely comfortable with it for some reason...)</p> <p>My questions are:</p> <ol> <li>Is there a good way for me to call Timer.Change and be able to know whether I managed to change it before the callback was queued to the threadpool? (I don't think so, but it doesn't hurt to ask...)</li> <li>Has anyone else implemented (what I term) a "pushback timer" like this? If so, I'd love to hear how you tackled the problem.</li> </ol> <p>This question is somewhat hypothetical in nature since I already have a couple of working solutions (based on Dispose and based on DateTime.Now)...I'm mainly interested in hearing performance-related suggestions (as I'll be "pushing back" the Timer VERY frequently).</p> <p>Thanks!</p>

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