On Mon, Jan 4, 2016 at 8:09 AM, Dominique Martinet <dominique.martinet@xxxxxx> wrote: > Peter Zijlstra wrote on Mon, Jan 04, 2016 at 04:59:15PM +0100: >> On Tue, Dec 29, 2015 at 10:43:26PM -0800, Andy Lutomirski wrote: >> > [add cc's] >> > >> > Hi scheduler people: >> > >> > This is relatively easy for me to reproduce. Any hints for debugging >> > it? Could we really have a bug in which processes that are >> > schedulable as a result of mutex unlock aren't always reliably >> > scheduled? >> >> I would expect that to cause wide-spread fail, then again, virt is known >> to tickle timing issues that are improbable on actual hardware so >> anything is possible. >> >> Does it reproduce with DEBUG_MUTEXES set? (I'm not seeing a .config >> here). > > The config has CONFIG_DEBUG_MUTEXES=y > > It got attached a while ago, reposting it here. > >> If its really easy you could start by tracing events/sched/sched_switch >> events/sched/sched_wakeup, those would be the actual scheduling events. > > I'm sure I've missed something in /Documentation but I'm not aware how > to trace these? (I'm happy to save Andy some precious time as I've got a > reproducer all set up now) My reproducer, at least, would make this tricky -- the system ends up mostly hung, so I don't know how I'd read out the result. Maybe I'd try to get something to dump the ftrace buffer to serial console after a delay and stick all that in initramfs where it wouldn't get stuck behind the same mutex as everything else. Or is there a way to tell the kernel to do that for us? --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
