mtd: pxa3xx_nand: issue with command time out

[Ezequiel Garcia]

On 3 March 2016 at 17:16, Hamish Martin
<Hamish.Martin at alliedtelesis.co.nz> wrote:
> Hi Ezequiel,
>
> I'm glad my analysis was correct and we more fully understand the
> problem now. CONFIG_PREEMPT seems to work for us now, but it does seem
> like the wrong fix, and if you guys think it will not guarantee
> preventing the issue then we'd rather back that change out.
>

Do you have any good reason for NOT enabling CONFIG_PREEMPT?

I've had very bad experiences on embedded systems when not
using CONFIG_PREEMPT, and came to the conclusion that
enable full preemption, unless there's a good reason not to.

Enabling CONFIG_PREEMPT would result in slightly lower throughput,
but maximum latency will be greatly reduced.

For instance, in a kernel without preemption, a UBI static volume check
(which happens on the first UBI static volume open call), can take
several seconds.

> I had contemplated using wait_for_completion_interruptible() but was a
> bit unsure if it was safe. Do you have a proposed patch? We would be
> happy to apply it to our system, turn off CONFIG_PREEMPT, and see how it
> goes. Out issue is highly reproducible so I think it would be a good
> first test for a change?
>

Sure, I can try to cook a patch for you.
-- 
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar