Re: preempt_disable() as synchronization tool

On Fri, Oct 9, 2009 at 9:13 AM, Daniel Rodrick <[email protected]> wrote:
> Hi List,
>
> I have few queries related to preempt_disable() and would appreciate
> any answers to it.
>
> Firstly, Does preempt_disable() disable the preemption on all the
> processors or on just the local processor?

I guess just local processor as the preempt count is maintained in
current thread_info struct. Correct me if I am wrong here.

>
> Secondly, a preempt_disable() a sufficient synchronization technique
> to guard a data that is shared only among process context code on a
> Uni-processor? And on SMP?

It is sufficient only in case of uni-processor (Actually spin_lock
also just disables preemption in case of uni-processor)

>
> Lastly, is it allowable to schedule / sleep immediately after a call
> to preempt_disable()?

No I guess kernel will panic with some error like , "scheduling while
in Atomic Context".

>
> Thanks & Best Regards,
>
> Dan
>
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