Messages in this thread | | | Date | Thu, 18 Jun 2015 09:30:16 -0700 | From | "Paul E. McKenney" <> | Subject | Re: perf: aux area related crash and warnings |
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On Thu, Jun 18, 2015 at 11:09:55AM +0200, Ingo Molnar wrote: > > * Alexander Shishkin <alexander.shishkin@linux.intel.com> wrote: > > > +void rb_free_aux(struct ring_buffer *rb) > > +{ > > + /* > > + * hold rb::refcount to make sure rb doesn't disappear > > + * before aux pages are freed > > + */ > > + if (WARN_ON_ONCE(!atomic_inc_not_zero(&rb->refcount))) > > + return; > > + > > + if (atomic_dec_and_test(&rb->aux_refcount)) > > + call_rcu(&rb->rcu_head, rb_free_rcu); > > + else > > + ring_buffer_put(rb); /* matches the increment above */ > > Is call_rcu() NMI-safe? I don't think so ...
Definitely not! ;-)
> I think the life time rules of this object are really messed up if they can be > freed from any fast path. How come the freeing can happen in NMI context? > Shouldn't the hardware first stop, then we can free things from the system call > path, or so? > > Thanks, > > Ingo >
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