There is something odd being reported in Ubuntu. There's a Mono SIGSEGV that was bisected to Andy's commit 1ddf0b1b11aa ("x86, vdso: Use asm volatile in __getcpu"), and then reported to be fixed with commits
80f7fdb1c7f0 ("x86: vdso: fix pvclock races with task migration") 0a4e6be9ca17 ("x86: kvm: Revert "remove sched notifier for cross-cpu migrations"") and when those were backported all looked well. But then those two commits in turn were reverted with 73459e2a1ada ("x86: pvclock: Really remove the sched notifier for cross-cpu migrations") and people seem to report that it's back as a result: https://bugzilla.xamarin.com/show_bug.cgi?id=29212#c16 so apparently that task migration notifier somehow does matter. Comments? Linus On Mon, May 16, 2016 at 1:13 AM, <okhal...@team.vestbery.com> wrote: > > Hello Linus, > > Am am sorry to bother you, but it seems that the bug from old kernels was > copied to new >=4.1 kernels. We use Ubuntu/Docker/Mono and we had to > rollback to 3.19.0-54 kernel for the work around. > > We found that a year ago there was a discussion on the launchpad > (https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1450584) regarding > SIGSEGV on multi-cpu vm. > It seems to me that the commits around that bug > https://github.com/torvalds/linux/commits/master/arch/x86/kernel/pvclock.c > caused 4.1 and up kernels to keep that bug. > Please review pvclock.c to fix that problem. > > Kiitos! Thank you! > > -- > Oleg Khalzov > SDE > Vestbery >