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SubjectRe: __update_max_tr: rcu_read_lock() used illegally while idle!
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On Tue, 2012-07-31 at 07:44 -0700, Paul E. McKenney wrote:

> > Found it (and Cc'd David).
> >
> > In __update_max_tr() we have:
> >
> > max_data = task_uid(tsk);
> >
> > where task_uid() is:
> >
> > #define task_uid(task) (task_cred_xxx((task), uid))
> >
> > #define task_cred_xxx(task, xxx) \
> > ({ \
> > __typeof__(((struct cred *)NULL)->xxx) ___val; \
> > rcu_read_lock(); \
> > ___val = __task_cred((task))->xxx; \
> > rcu_read_unlock(); \
> > ___val; \
> > })
> >
> > The __update_max_tr() is called at every location interrupts are enabled
> > (and a max time is discovered). But now this can include places that
> > rcu_read_lock can not be called, I'm not sure how to handle this. Is
> > there a non rcu way to get a tasks uid?
>
> OK, I will bite. How about using something like RCU_NONIDLE(), either
> directly or open-coded, to make it a legal call site?

OK, then something like:

RCU_NONIDLE(max_data = task_uid(tsk));

would work when called normally or with idle?

-- Steve




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