On 16/05/2016 20:56, Linus Torvalds wrote: > On Mon, May 16, 2016 at 11:37 AM, Andy Lutomirski <l...@amacapital.net> wrote: >> >> All of those fixes were intended to fix incorrect times being >> reported, not segfaults. Weird. > > I'm assuming it's "time going backwards". I can easily see that > causing segfaults.
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1450584 says the crashes occurs "more frequently on a vbox vm with multiple CPUs configured". If vbox tells the VM to use the vdso when it shouldn't (because the TSC is not stable on the host), bad things could happen. However, based on the Xamarin bug comments and http://lists.ximian.com/pipermail/mono-devel-list/2015-August/043181.html, it looks like vbox after all doesn't use pvclock and the trigger seems to be https://github.com/torvalds/linux/commit/c70e1b475f37: With __always_inline on vread_pvclock, mono crashed. With noinline on vread_pvclock, mono doesn't crash. Weirdest part is that the pvclock isn't even used during my tests. Oleg, what is your environment exactly? You mentioned Docker, but are you also virtualizing and if so what is your hypervisor? Taloth, do you know if it can it be reproduced under Xen or KVM or bare-metal? I'd trust them more than VirtualBox regarding timekeeping. I saw Amazon Linux mentioned in the mono mailing list archives which would point to Xen. Xen doesn't use the pvclock vdso code either, though. Thanks, Paolo
