[UPSTREAM] Attempt at improving ADC access

[Andy Green]

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Somebody in the thread at some point said:
| On Thu, Oct 16, 2008 at 12:18:50AM +0100, Andy Green wrote:
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|> Somebody in the thread at some point said:
|>
|> | Also, don't the queue head/tail manipulation functions require
locking ?
|>
|> When I wrote them I recall coming to the idea that no locking is needed
|> because each of the "threads" only controls the head or the tail
|> exclusively.
|>
|
| Hmm.. I don't understand. Since the queue update statement is not
| atomic, it could be preempted anywhere 'in between' by an interrupt
| handler which might also want to add to the queue. This can lead
| to problems. Isn't it? Is there any reason why this can't happen ?
| Please explain.

The explanation is you are quite right... it should lock interrupts in
the add to queue thing.  Maybe you can take care of this?

- -Andy
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