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. 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. -- 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/
