When is to preempt safe?

[Daniel Baluta]

On Sat, Oct 8, 2011 at 7:19 PM, Parmenides <mobile.parmenides at gmail.com> wrote:
> 2011/10/8 Chetan Nanda <chetannanda at gmail.com>:
>>
>> New task pick by scheduler may try to get the same lock resulting in
>> deadlock
>
> It seems that this kind of deadlock may be removed eventually. Suppose
> that we have a task A, which is holding a spinlock. If A is preempted
> by task B which try to obtain the same spinlock. Although B has to
> busy wait, it will end up with be preempted owing to using up its
> timeslice. Therefore, A has chance to be selected by shechedler and
> release the spinlock. Then, B will go on when it is selected by the
> secheduler next time.

Well, I think that if task B has higher priority than task A, then A would
never have the chance to release the lock.

thanks,
Daniel.