Messages in this thread | | | Date | Tue, 24 Apr 2001 08:40:58 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] rw_semaphores, optimisations try #3 |
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On Tue, 24 Apr 2001, David Howells wrote: > > Yes but the "struct rwsem_waiter" batch would have to be entirely deleted from > the list before any of them are woken, otherwise the waking processes may > destroy their "rwsem_waiter" blocks before they are dequeued (this destruction > is not guarded by a spinlock).
Look again.
Yes, they may destroy the list, but nobody cares.
Why?
- nobody will look up the list because we do have the spinlock at this point, so a destroyed list doesn't actually _matter_ to anybody
You were actually depending on this earlier, although maybe not on purpose.
- list_remove_between() doesn't care about the integrity of the entries it destroys. It only uses, and only changes, the entries that are still on the list.
Subtlety is fine. It might warrant a comment, though.
Linus
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