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SubjectRe: waiting on a condition
Have you looked at the wait_event() family yet?       Adapting that 
methodolgy might
suit your needs.

I don't know much about preemption yet, however I suspect it would be a
bug to allow
preemption while the spinlock was held. In other words, you might need
to do something like

disable preemption
spinlock
rc = condition
spin_unlock
enable preemption
if (rc)
...

In other words, perform the test on the condition outside of the
critical region protected by the spin lock.

-PWM


Martijn Sipkema wrote:

>L.S.
>
>I'd like to do something similar as can be done using a POSIX condition
>variable in the kernel, i.e. wait for some condition to become true. The
>pthread_cond_wait() function allows atomically unlocking a mutex and
>waiting on a condition. I think I should do something like:
>(the condition is updated from an interrupt handler)
>
>disable interrupts
>acquire spinlock
>if condition not satisfied
> add task to wait queue
> set task to sleep
>release spinlock
>restore interrupts
>schedule
>
>Now, this will only work with preemption disabled within the critical
>section. How would something like this be done whith preemption
>enabled?
>
>
>--ms
>
>
>
>
>-
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--
Peter W. Morreale email: morreale@radiantdata.com
Director of Engineering Niwot, Colorado, USA
Radiant Data Corporation voice: (303) 652-0870 x108
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