Re: Real-Time Preemption and RCU

[Esben Nielsen]

On Tue, 22 Mar 2005, Ingo Molnar wrote:

> 
> * Esben Nielsen <simlo@xxxxxxxxxx> wrote:
> 
> > +static inline void rcu_read_lock(void)
> > +{	
> > +	preempt_disable(); 
> > +	__get_cpu_var(rcu_data).active_readers++;
> > +	preempt_enable();
> > +}
> 
> this is buggy. Nothing guarantees that we'll do the rcu_read_unlock() on
> the same CPU, and hence ->active_readers can get out of sync.
> 

Ok, this have to be handled in the mitigration code somehow. I have already 
added an 
  current->rcu_read_depth++
so it ought to be painless. A simple solution would be not to mititagrate
threads with rcu_read_depth!=0.

> 	Ingo
> 

Esben

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