]> git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/commit
arm64: topology: Avoid checking numa mask for scheduler MC selection
authorJeremy Linton <jeremy.linton@arm.com>
Fri, 12 Oct 2018 17:48:44 +0000 (12:48 -0500)
committerKhalid Elmously <khalid.elmously@canonical.com>
Tue, 23 Oct 2018 06:45:58 +0000 (08:45 +0200)
commit96410fcd8ba3e5029dc8107e1f928a81841fe3be
tree0b3b3fa9a55f8fc32ff9ed63ca36ca33e26ce8ae
parent8abc340044a54dfe88ea91f0dce37c75da3fe3aa
arm64: topology: Avoid checking numa mask for scheduler MC selection

The numa mask subset check can often lead to system hang or crash during
CPU hotplug and system suspend operation if NUMA is disabled. This is
mostly observed on HMP systems where the CPU compute capacities are
different and ends up in different scheduler domains. Since
cpumask_of_node is returned instead core_sibling, the scheduler is
confused with incorrect cpumasks(e.g. one CPU in two different sched
domains at the same time) on CPU hotplug.

Lets disable the NUMA siblings checks for the time being, as NUMA in
socket machines have LLC's that will assure that the scheduler topology
isn't "borken".

The NUMA check exists to assure that if a LLC within a socket crosses
NUMA nodes/chiplets the scheduler domains remain consistent. This code will
likely have to be re-enabled in the near future once the NUMA mask story
is sorted.  At the moment its not necessary because the NUMA in socket
machines LLC's are contained within the NUMA domains.

Further, as a defensive mechanism during hot-plug, lets assure that the
LLC siblings are also masked.

BugLink: http://launchpad.net/bugs/1797202
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit e156ab71a974737c279530e3b868131291fe677e)
Signed-off-by: Manoj Iyer <manoj.iyer@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
arch/arm64/kernel/topology.c