Re: [PATCH 1/1] stp: rt: force to enable preempt

[yzhu1 <Yanjun dot Zhu at windriver dot com>]

On 10/26/2015 10:21 PM, Frank Ch. Eigler wrote:
> Zhu Yanjun <yanjun.zhu@windriver.com> writes:
>
> > -rt mode preempt lead to __might_sleep calltrace.
> > Enabling preempt solves the problem.
> > [...]
> > After this patch is applied, the above backtrace disappears.
> Could you elaborate why this change is a good idea, beyond defeating
> the kernel warning?  (It is possible that the warning is less bad than
> a race condition or something that preemption in that area might
> enable.)
>
> - FChE
Hi,

Thanks for your reply.

Yes, this patch will introduce the race condition risk. But if this is 
not enabled,
-rt system can not get the preemption.

In a -rt system, I think it is the first. Compared with the race 
condition risk, I think
preemption is more important.

Sometimes we can not get the both(less race condition risk and better rt 
preemption),
we have to pay more attention to one side.

This patch pays more attention to rt preemption. So maybe the race 
condition is payed less
attention.

Best Regards!
Zhu Yanjun