Tianyu reported a crash with SMP=y and HOTPLUG_CPU=n plus 'nosmt' on the kernel command line.
https://lkml.kernel.org/r/1553521883-20868-1-git-send-email-tianyu....@microsoft.com The reason is a bug in the hotplug code which does not handle the fact, that HOTPLUG_CPU=n cannot tear down a CPU completely. Unfortunately HOTPLUG_CPU cannot be enforced as some architectures do not support it at all. The fix is only a workaround because a full solution is not possible due to the limitations of HOTPLUG_CPU=n. So the CPU stays around in an undead state. As 'nosmt' has become popular recently, the proper solution for X86 is to enforce HOTPLUG_CPU when SMP is enabled. Thanks, tglx ---- arch/x86/Kconfig | 8 +------- kernel/cpu.c | 20 ++++++++++++++++++-- 2 files changed, 19 insertions(+), 9 deletions(-)
