cc'ing Marcelo On Mon, Dec 22, 2014 at 04:06:02PM +1100, Cyril Bur wrote: > When the hypervisor pauses a virtualised kernel the kernel will observe a jump > in timebase, this can cause spurious messages from the softlockup detector. > > Whilst these messages are harmless, they are accompanied with a stack trace > which causes undue concern and more problematically the stack trace in the > guest has nothing to do with the observed problem and can only be misleading. > > Futhermore, on POWER8 this is completely avoidable with the introduction of > the Virtual Time Base (VTB) register.
Hi Cyril, Your solution seems simple and doesn't disturb the softlockup code as much as the x86 solution does. The only small issue I had was the use of sched_clock instead of local_clock. I keep forgetting the difference (unstable clock is the biggest reason I think). Other than that, I am not the biggest fan of putting multiple virtual guest solutions for the same problem into the watchdog code. I would prefer a common solution/framework to leverage. I have the x86 folks focusing on the steal_time stuff. It started with KVM and I believe VMWare is working on utilizing it too (and maybe Xen). Not sure if that is useful or could be incoporated into the power8 code. Though to be honest I am curious if the steal_time code could be ported to your solution as it seems the watchdog code could remove all the steal_time warts. I have cc'd Marcelo into this discussion as he was the last person I remember talking with about this problem. Cheers, Don -- 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/
