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SubjectRe: [PATCH RFC tip/core/rcu 05/11] rcu: add comment saying why DEBUG_OBJECTS_RCU_HEAD depends on PREEMPT.
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On Wed, 2011-02-23 at 08:59 -0500, Mathieu Desnoyers wrote:

> #ifdef CONFIG_PREEMPT
> /*
> * Ensure that queued callbacks are all executed.
> * If we detect that we are nested in a RCU read-side
> * critical
> * section, we should simply fail, otherwise we would
> * deadlock.
> */
> if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
> irqs_disabled()) {
> WARN_ON(1);
> return 0;
> }
> rcu_barrier();
> rcu_barrier_sched();
> rcu_barrier_bh();
> debug_object_init(head, &rcuhead_debug_descr);
> return 1;
> #else
> return 0;
> #endif
>
> instead, no ?

BTW, if you do end up doing such a thing...

#ifndef CONFIG_PREEMPT
return 0;
#endif

before all that would be much cleaner.

Just make sure any non defined in PREEMPT macros/functions are defined
as nops in !CONFIG_PREEMPT

-- Steve




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