Re: [PATCH 6/6] cpuset dirty limits

[Christoph Lameter]

On Fri, 14 Sep 2007, Andrew Morton wrote:

> > +	mutex_lock(&callback_mutex);
> > +	*cs_int = val;
> > +	mutex_unlock(&callback_mutex);
> 
> I don't think this locking does anything?

Locking is wrong here. The lock needs to be taken before the cs pointer 
is dereferenced from the caller.

> > +	return 0;
> > +}
> > +
> >  /*
> >   * Frequency meter - How fast is some event occurring?
> >   *
> > ...
> > +void cpuset_get_current_ratios(int *background_ratio, int *throttle_ratio)
> > +{
> > +	int background = -1;
> > +	int throttle = -1;
> > +	struct task_struct *tsk = current;
> > +
> > +	task_lock(tsk);
> > +	background = task_cs(tsk)->background_dirty_ratio;
> > +	throttle = task_cs(tsk)->throttle_dirty_ratio;
> > +	task_unlock(tsk);
> 
> ditto?

It is required to take the task lock while dereferencing the tasks cpuset 
pointer.
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