Re: [RFC patch 17/18] MIPS : Trace clock

Mathieu Desnoyers
2008-11-07T17:44:57Z

* Peter Zijlstra (a.p.zijlstra@chello.nl) wrote:
> On Fri, 2008-11-07 at 00:23 -0500, Mathieu Desnoyers wrote:
> > Note for Peter Zijlstra :
> > You should probably have a look at lockdep.c raw_spinlock_t lockdep_lock usage.
> > I suspect it may be used with preemption enabled in graph_lock(). (not sure
> > though, but it's worth double-checking.
>
> Are you worried about the graph_lock() instance in
> lookup_chain_cache() ?
>
> That is the locking for validate_chain,
>
> __lock_acquire()
> validate_chain()
> look_up_chain_cache()
> graph_lock()
> check_prevs_add()
> check_prev_add()
> graph_unlock()
> graph_lock()
> graph_unlock()
>
> which is all done without modifying IRQ state.
>
> However, __lock_acquire() is only called with IRQs disabled:
>
> lock_acquire()
> raw_local_irq_save()
> __lock_acquire()
>
> lock_release()
> raw_local_irq_save()
> __lock_release()
> lock_release_nested()
> __lock_acquire()
> lock_release_non_nested()
> __lock_acquire()
>
> lock_set_subclass()
> raw_local_irq_save()
> __lock_set_subclass()
> __lock_acquire()
>
> So I think we're good.
>

Yep, looks good.

Mathieu

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Mathieu Desnoyers
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