On Sat, Nov 09, 2013 at 03:10:39PM +0100, Peter Zijlstra wrote: > On Fri, Nov 08, 2013 at 11:36:58PM +0100, Frederic Weisbecker wrote: > > [ 237.627769] perf samples too long (3397569 > 2500), lowering > > kernel.perf_event_max_sample_rate to 50000 > > [ 237.637124] INFO: NMI handler (perf_event_nmi_handler) took too long to > > run: 444.233 msecs > > > > 444 msecs is huge. > > Be glad your system lived to tell about it ;-) Calling printk() from NMI > context is Russian roulette; I'm still waiting for the first report it > actually locked up :-)
Haha, right. I dump with earlyprintk but that doesn't change the fact it passes through printk machinery. Fortunately I haven't yet got burdened with that. Although... maybe printk plays a role in the issue here... > > That said, I'm not sure what kernel you're running, but there were some > issues with time-keeping hereabouts, but more importantly that second > timing includes the printk() call of the first -- so that's always going > to be fucked. It's a recent tip:master. So the delta debug printout is certainly buggy, meanwhile these lockup only happen with Vince selftests, and they trigger a lot of these NMI-too-long issues, or may be that's the other way round :)... I'm trying to narrow down the issue, lets hope the lockup is not actually due to printk itself. -- 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/