[PATCH V2] lglock: add read-preference local-global rwlock

[Michel Lespinasse]

On Sun, Mar 3, 2013 at 9:40 AM, Oleg Nesterov <oleg at redhat.com> wrote:
>> However, I still think that FALLBACK_BASE only adds the unnecessary
>> complications. But even if I am right this is subjective of course, please
>> feel free to ignore.

Would it help if I sent out that version (without FALLBACK_BASE) as a
formal proposal ?

> Hmm. But then I do not understand the lglock annotations. Obviously,
> rwlock_acquire_read() in lg_local_lock() can't even detect the simplest
> deadlock, say, lg_local_lock(LOCK) + lg_local_lock(LOCK). Not to mention
> spin_lock(X) + lg_local_lock(Y) vs lg_local_lock(Y) + spin_lock(X).
>
> OK, I understand that it is not easy to make these annotations correct...

I am going to send out a proposal to fix the existing lglock
annotations and detect the two cases you noticed. It's actually not
that hard :)

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.