SharpSvn SvnClient.GetLog throws AccessViolationException

Question

My application is crashing with the following unhandled exception:

System.AccessViolationException was unhandled
  HResult=-2147467261
  Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
  Source=SharpSvn
  StackTrace:
       at apr_pool_destroy(apr_pool_t* )
       at SharpSvn.Implementation.AprPool.Destroy()
       at SharpSvn.Implementation.AprPool.Dispose(Boolean )
       at SharpSvn.Implementation.AprPool.Dispose()
       at SharpSvn.SvnClient.InternalLog(ICollection`1 targets, Uri logRoot, SvnRevision altPegRev, SvnLogArgs args, EventHandler`1 logHandler)
       at SharpSvn.SvnClient.Log(Uri target, SvnLogArgs args, EventHandler`1 logHandler)
       at SharpSvn.SvnClient.GetLog(Uri target, SvnLogArgs args, Collection`1& logItems)
       at SourceLog.Plugin.Subversion.SubversionPlugin.CheckForNewLogEntries(Object state)
       at System.Threading.TimerQueueTimer.CallCallbackInContext(Object state)
       at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
       at System.Threading.TimerQueueTimer.CallCallback()
       at System.Threading.TimerQueueTimer.Fire()
       at System.Threading.TimerQueue.FireQueuedTimerCompletion(Object state)
       at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
       at System.Threading.ThreadPoolWorkQueue.Dispatch()
       at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
  InnerException: 

The call to SharpSvn.SvnClient.GetLog is here: https://github.com/tomhunter-gh/SourceLog/blob/2fa0632665550c18c9cd23500610704e3eaa35a2/SourceLog.Plugin.Subversion/SubversionPlugin.cs#L39

Answer 1

Looks like this is due to multiple timer callback instances calling GetLog at the same time and the fact that the method (SharpSvn in general?) isn't thread-safe. I've added a static lock object to ensure only one thread calls GetLog at a time.