On Thu, Nov 14, 2013 at 04:33:01PM +0100, Peter Zijlstra wrote: > On Thu, Nov 14, 2013 at 04:23:04PM +0100, Peter Zijlstra wrote: > > /* > > + * We must dis-allow sampling irq_work_exit() because perf event sampling > > + * itself can cause irq_work, which would lead to an infinite loop; > > + * > > + * 1) irq_work_exit happens > > + * 2) generates perf sample > > + * 3) generates irq_work > > + * 4) goto 1 > > + */ > > +TRACE_EVENT_PERF_PERM(irq_work_exit, is_sampling_event(p_event) ? -EPERM : > > 0); > > And the only reason this doesn't feed fwd itself into oblivion for > irq_work_enter() is because the irq_work_list must not be empty when the > interrupt is raised, and queueing further work does not re-raise the > IPI.
Right. > > > Also, we should probably do something 'smart' for kprobes, as all of > irq_work.c and plenty of perf itself is not __kprobe marked so you're > all free to insert kprobes in the middle of perf and then attach perf to > such a thing. > True, ok I'm going to comment about that on your patch. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/