Re: [patch 05/15] Generic Mutex Subsystem, mutex-core.patch

[Ingo Molnar]

* Oleg Nesterov <oleg@xxxxxxxxxx> wrote:

> But why we can't add the waiter to ->wait_list _after_ xchg() ? What 
> makes the difference? Fastpath atomic op can happen before or after 
> xchg(), this is ok. Unlock path will look at ->wait_list only after 
> taking spinlock, at this time we already added this waiter to the 
> ->wait_list.
> 
> In other words: we are holding ->wait_lock, nobody can even look at 
> ->wait_list. We can add the waiter to ->wait_list before or after 
> atomic_xchg() - it does not matter.

hm, you are right - i've added this optimization.

	Ingo
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