On Thu, 2007-08-16 at 09:01 -0700, Paul E. McKenney wrote:
> On Thu, Aug 16, 2007 at 04:25:07PM +0200, Peter Zijlstra wrote:
> >
> > There seem to be some unbalanced rcu_read_{,un}lock() issues of late,
> > how about doing something like this:
>
> This will break when rcu_read_lock() and rcu_read_unlock() are invoked
> from NMI/SMI handlers -- the raw_local_irq_save() in lock_acquire() will
> not mask NMIs or SMIs.
>
> One approach would be to check for being in an NMI/SMI handler, and
> to avoid calling lock_acquire() and lock_release() in those cases.
It seems:
#define nmi_enter() do { lockdep_off(); __irq_enter(); } while (0)
#define nmi_exit() do { __irq_exit(); lockdep_on(); } while (0)
Should make it all work out just fine. (for NMIs at least, /me fully
ignorant of the workings of SMIs)
> Another approach would be to use sparse, which has checks for
> rcu_read_lock()/rcu_read_unlock() nesting.
Yeah, but one more method can never hurt, no? :-)
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