On Wed, Jun 18, 2014 at 11:32:53PM +0200, Jiri Kosina wrote: > On Wed, 18 Jun 2014, Paul E. McKenney wrote: > > > > I agree that it might work nicely for RCU stall detector indeed. I was > > > looking for solution that'd work nicely both for RCU and for sysrq-l > > > (where we can't rely on processess being stuck in any way). > > > > Agreed. And if some more generally useful approach appears, I will be > > quite happy to adjust RCU to use it. In the meantime, I expect that > > my patch will be helpful. > > Agreed. And we'll look into fixing sysrq-l in parallel I guess; once there > is a working solution (hangs with sysrq-l can be trivially reproduced > almost immediately), we can then migrate RCU to it. > > Still, I feel bad about the fact that we are now hostages of our printk() > implementation, which doesn't allow for any fixes/improvements. Having the > possibility to printk() from NMI would be nice and more robust ... > otherwise, we'll be getting people trying to do it in the future over and > over again, even if we now get rid of it at once.
Well, we could always have printk() splat if invoke in_nmi(). Oh, wait... ;-) More seriously, an in_nmi() printk() could taint the kernel, set a flag that results in a deferred splat, do a trace_printk(), or any number of things to let the developer know that this was a bad idea. Thanx, Paul -- 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/