Kernel lock order

Is there a list describing the lock hierarchy ?
If not:
Does do_swap_page() (in mm/memory.c) release mm->page_table_lock because one cannot hold this lock when lookup_swap_cache() ... __find_get_page() takes pagecache_lock ? Or does it do only for shorten the locked path ? (Can I keep mm->page_table_lock when I call __find_get_page() ?)

Thanks,

Zoltan Menyhart

There is indeed Documentation/vm/locking - but I wouldn't trust it for an instant! These details change from time to time, Documentation is likely to lag far behind, the source must be your reference.

There is also a very useful "NOTE:" in the 2.4 mm/filemap.c, which did get updated in 2.4.14; but that doesn't mention the page_table_lock.

I deduce from "pagecache_lock" that you're asking about current 2.4, though I think an equivalent answer would apply to current 2.5. It does it to shorten the locked path, you could hold mm->page_table_lock when you call __find_get_page(): a precedent is where do_swap_page() holds page_table_lock while calling remove_exclusive_swap_page(), which may take the pagecache_lock.

But tomorrow... who knows?

Hugh