Re: hashed waitqueues

[Andrew Morton <akpm@zip.com.au>]

Andrew Morton wrote:
> 
> > +       /*
> > +        * Although the default semantics of wake_up() are
> > +        * to wake all, here the specific function is used
> > +        * to make it even more explicit that a number of
> > +        * pages are being waited on here.
> > +        */
> > +       if(waitqueue_active(page_waitqueue(page)))
> > +               wake_up_all(page_waitqueue(page));
> ...
> 
> Also, why wake_up_all()?  That will wake all tasks which are sleeping
> in __lock_page(), even though they've asked for exclusive wakeup
> semantics.  Will a bare wake_up() here not suffice?
> 

Doh.  It helps to read the comment.  Suggest that __lock_page()
be changed to use add_wait_queue().

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