Re: [RFC,PATCH] use rcu for fasync_lock

[Manfred Spraul]

Jamie Lokier wrote:

> Manfred Spraul wrote:
>  
>
> > What about switching to rcu?
> >    
>
> What about killing fasync_helper altogether and using the method that
> epoll uses to register "listeners" which send a signal when the poll
> state of a device changes?
I think it would be a step in the wrong direction: poll should go away 
from a simple wake-up to an interface that transfers the band info 
(POLL_IN, POLL_OUT, etc). Right now at least two passes over the f_poll 
functions are necessary, because the info which event actually triggered 
is lost. kill_fasync transfers the band info, thus I don't want to 
remove it.

> That would trim off code all over the place, make the fast paths a
> little bit faster (in the case that there aren't any listeners), and
> most importantly make SIGIO reliable for every kind of file descriptor,
> instead of the pot luck you get now.
>
> Just an idea :)
It's a good idea, but requires lots of changes - perhaps it will be 
necessary to change the pollwait and f_poll prototypes.

--
   Manfred

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