Re: lockdep oddity

Ingo Molnar
2006-09-05T19:45:57Z

* Ingo Molnar <mingo@elte.hu> wrote:

> * Ingo Molnar <mingo@elte.hu> wrote:
>
> > > The reason is that the BUILD_LOCK_OPS macros in kernel/lockdep.c
> > > don't contain any of the *_acquire calls, while all of the _unlock
> > > functions contain a *_release call. Hence I get immediately
> > > unbalanced locks.
> >
> > hmmm ... that sounds like a bug. Weird - i recently ran
> > PREEMPT+SMP+LOCKDEP kernels and didnt notice this.
>
> ok, the reason i didnt find this problem is because this is fixed in
> my tree, but i didnt realize that it's a fix also for upstream ...

actually ... it works fine in the upstream kernel due to this:

* If lockdep is enabled then we use the non-preemption spin-ops
* even on CONFIG_PREEMPT, because lockdep assumes that interrupts are
* not re-enabled during lock-acquire (which the preempt-spin-ops do):
*/
#if !defined(CONFIG_PREEMPT) || !defined(CONFIG_SMP) || \
defined(CONFIG_DEBUG_LOCK_ALLOC)

so i'm wondering, how did you you manage to get into the
BUILD_LOCK_OPS() branch?

Ingo