Re: race condition in schedule_on_each_cpu()

[weiqi@xxxxxxxxxxxxxx]

In the previous  message,You mentioned:


> > by the way, I'm wondering about  what's the race condition before
which  doesn't exist now


> Before the commit you originally quoted, the calling thread could be
preempted and migrated to another CPU before get_online_cpus() thus
ending up executing the function twice on the new cpu but skipping the
old one.


does this situation will happen in "Full preemption" config, on 3.0.30-rt50?







ä 2013å06æ07æ 09:34, weiqi@xxxxxxxxxxxxxx åé:
> it's preemption mode related ,
>
> on the 3.0.30-rt50, only   config kernel  with highest preemption 
> level (Fully Preemptible Kernel (RT)) in cpu preemption model
> will cause problem
>
> and even i use the "Preemptible Kernel" or "Preemptible Kernel 
> (Low-Latency Desktop)"  the problem would not happen..
>
>
> > I looked through the logs but the only worker depletion related 
> patches which pop up are around CPU hotplugs, so I don't think they 
> apply here. If the problem is relatively easy to reproduce && you 
> can't move onto a newer kernel, I'm afraid bisection probably is the 
> best option. Thanks!


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