My application needs to read files from a nfs mount point. I'm using QFile::read(BUFFER_SIZE); which works as it is supposed to. The problem is, when the nfs unmounts (patchy network issues), this QFile::read() never timesout resulting in application hang. Any sensible solutions please?
Thanks.
I think this is due to how NFS works. The process is stuck in the OS system call, in uninterruptible sleep. So, I think you have two reliable options:
Move file reading to another thread. It and its event loop may get stuck, just code your main thread so that it won't matter for the whole application. There are a few ways to go about using threads for this, but if you are not reading arbitrary number of different files at the same time, it'd probably be best to launch a dedicated thread for reading the single file, and then let the thread finish once everything is read. For this, you might even just subclass QThread, and override run() method with your own reading loop (you can still emit signals for progress if you want, you just can't receive them queued without Qt's event loop).
Move file reading to another process. In other words, write a small tool program or script which does the actual reading, and sends the contents to your main process. That way you should be able to kill the reading process without killing the whole application, should that become necessary. Again you have to decide if you want a separate single-use process for each reading (so you can give file name as command line paramater, for example), or if you launch one child process and implement communication with it so you can request files (or parts of files). Qt's QProcess makes this approach easy, too.