Why it's harder than it looks

Why it's harder than it looks

Posted Aug 1, 2003 16:48 UTC (Fri) by giraffedata (subscriber, #1954)
In reply to: Why it's harder than it looks by Peter
Parent article: A different approach to module races

Here's one more, that rarely gets attention:

- Any time you create a new thread executing the module code, you need a reference. The reference must exist from before the thread gets created to after the thread is dead.

By the way, there are two kinds of references involved. One type prevents the module unloader from attempting an unload. The other tells the module itself whether it's safe to be unloaded. The difference is that the module is capable of undoing some references or waiting for them to go away, whereas the module unloader isn't. E.g. while the module has a major number registered, it has a reference and cannot unload. But you wouldn't want rmmod to fail just because that reference exists. The module cleanup function can undo that reference by unregistering the major number.

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