* Greg KH (greg@xxxxxxxxx) wrote: > On Thu, Dec 01, 2011 at 04:57:00PM -0500, Christoph Hellwig wrote: > > On Thu, Dec 01, 2011 at 04:41:13PM -0500, Mathieu Desnoyers wrote: > > > LTTng needs this symbol exported. It calls it to ensure its tracing > > > buffers and allocated data structures never trigger a page fault. This > > > is required to handle page fault handler tracing and NMI tracing > > > gracefully. > > > > We: > > > > a) don't export symbols unless they have an intree-user > > lttng is now in-tree in the drivers/staging/ area. See linux-next for > details if you are curious. > > > b) especially don't export something as lowlevel as this one. > > Mathieu, there's nothing else you can do to get this information? Or > does lttng really want such lowlevel data? LTTng calls vmalloc_sync_all() to make sure it won't crash the system (due to recursive page fault) when hooking on the page fault handler and on any hook that would happen to sit in a function hit by NMI context. So it really goes beyond just extracting information for this one I'm afraid: it's a matter of execution correctness. This is a point I'm really anal about: the tracer should _never_ crash the traced system, _ever_, in any foreseeable condition. Thanks, Mathieu > > thanks, > > greg k-h -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>