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Currently I am working on a Delphi XE3 client/server application to transfer files (with the Indy FTP components). The client part monitors a folder, gets a list of the files inside, uploads them to the server and deletes the originals. The uploading is done by a separate thread, which processes files one by one. The files can range from 0 to a few thousand and their sizes also vary a lot. It is a Firemonkey app compiled for both OSX and Windows, so I had to use TThread instead of OmniThreadLibrary, which I preferred. My customer reports that the application randomly freezes. I could not duplicate it, but since I don't have so much experience with TThread, I might have put deadlock condition somewhere. I read quite a lot of examples, but I'm still not sure about some of the multithread specifics. The app structure is simple: A timer in the main thread checks the folder and gets information about each file into a record, which goes into a generic TList. This list keeps information about the names of the files, size, the progress, whether the file is completely uploaded or has to be retried. All that is displayed in a grid with progress bars, etc. This list is accessed only by the main thread. After that the items from the list are sent to the thread by calling the AddFile method (code below). The thread stores all files in a thread-safe queue like this one http://delphihaven.wordpress.com/2011/05/06/using-tmonitor-2/ When the file is uploaded the uploader thread notifies the main thread with a call to Synchronize. The main thread periodically calls the Uploader.GetProgress method to check the current file progress and display it. This function is not actually thread-safe, but could it cause a deadlock, or only wrong data returned? What would be a safe and efficient way to do the progress check? So is this approach OK or I have missed something?

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