Re: preempt_disable() as synchronization tool

[vinit dhatrak <vinit.dhatrak@xxxxxxxxx>]

On Sat, Oct 10, 2009 at 10:16 AM, askb <askb23@xxxxxxxxx> wrote:
>
>> >
>> > 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".
>
> Sorry, I somehow missed out reading this. Can you let me know why its
> not possible to schedule within preempt_disable() and preempt_enable()?
> >From the code the schedule functions starts by disabling preemption?
> Thanks in advance. - Anil
>
>

Because, preempt_disable increments the preempt count and before
scheduling the next task, schedule() function checks for the preempt
count for the previous task. If its greater than 0 then it will throw
an error "BUG: scheduling while atomic:"

-Vinit
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