Databases
StackOverflow2013
Postsdbo
POIssue with ManualResetEvent not releasing all waiting threads consistently
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POIssue with ManualResetEvent not releasing all waiting threads consistently
    primarykey
    data
    text
    <p>I'm trying to implement a class which uses a simple cache for holding data retrieved from an internal service. I'm using a ManualResetEvent to block multiple threads which may try to refresh the cached data at the same time with the first thread to succeed signalling the others to proceed once the data has been retrieved by calling Set() and then Reset(). When testing I've noticed that sometimes all of the threads are released and sometimes 1 or more are not and are left to time out, almost as if I am calling Reset before all of the threads were released. Can someone explain what I am doing wrong?</p> <p>I've included a cut down version of the code below.</p> <pre><code> private bool _updating; private const int WaitTimeout = 20000; private DateTime _lastRefresh; private object _cacheData; private readonly ManualResetEvent _signaller = new ManualResetEvent(false); private void RefreshCachedData() { Console.WriteLine("ThreadId {0}: Refreshing Cache", Thread.CurrentThread.ManagedThreadId); if (_updating) { Console.WriteLine("ThreadId {0}: Cache Refresh in progress, waiting on signal.", Thread.CurrentThread.ManagedThreadId); // another thread is currently updating the cache so wait for a signal to continue if (!_signaller.WaitOne(WaitTimeout)) Console.WriteLine("ThreadId {0}: Thread timed out ({1}s) waiting for a signal that the cache had been refreshed", Thread.CurrentThread.ManagedThreadId,WaitTimeout); Console.WriteLine("ThreadId {0}: Signal recieved to use refreshed cache.", Thread.CurrentThread.ManagedThreadId); } else { try { _updating = true; var result = _requestHandler.GetNewData(); if (!result.Success) { Console.WriteLine("Failed to retrieve new data."); } else { // switch the cache with the new data _cacheData = result.Data; Console.WriteLine( "ThreadId {0}: Cache refresh success.", Thread.CurrentThread.ManagedThreadId); Thread.Sleep(8000); } } catch (Exception ex) { Console.WriteLine("Error occured: {0}", ex); } finally { // Set the refresh date time regardless of whether we succeded or not _lastRefresh = DateTime.Now; _updating = false; // signal any other threads to to carry on and use the refreshed cache Console.WriteLine("ThreadId {0}: Signalling other threads that cache is refreshed.", Thread.CurrentThread.ManagedThreadId); _signaller.Set(); _signaller.Reset(); } } } </code></pre>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USgouldos
    1. USgouldos
    plurals
    1. This table or related slice is empty.
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POIssue with ManualResetEvent not releasing all waiting threads consistently
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POIssue with ManualResetEvent not releasing all waiting threads consistently
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POIssue with ManualResetEvent not releasing all waiting threads consistently
      1. This table or related slice is empty.
      1. VTUpMod
    1. CO`Thread.Sleep(8000)` and `WaitOne` sounds like it wont play along nicely.
      singulars
      1. POIssue with ManualResetEvent not releasing all waiting threads consistently
      1. USleppie
    2. COThe Thread sleep was there just for the purposes off testing to make sure that all the other threads entered the wait before the thread refreshing the cache released them
      singulars
      1. POIssue with ManualResetEvent not releasing all waiting threads consistently
      1. USgouldos
    3. COThis may be a red herring but if I put a thread sleep of 50ms between the set and reset, I have yet to see in testing any of the threads not be released.
      singulars
      1. POIssue with ManualResetEvent not releasing all waiting threads consistently
      1. USgouldos
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload