Comment 107 for bug 93546

So what should FirefoxB do when FirefoxA has the history file locked and it wants to update it? Queue those things for later? Block the UI? How should it communicate to the calling code that the write it wanted didn't really complete? How to keep other code in that app from reading stale data?

We could litter our code with O_NONBLOCK/WOULDBLOCK checks, but that is neither easy nor nice. I don't know of other applications that store profile-like data as frequently as we do (browsing history), and manage to not interfere with other instances. If you can point us at some, we might be able to adapt their techniques.