lp:~arighi/ubuntu/+source/linux-aws/+git/groovy

Author: Eduardo Valentin
Author Date: 2018-04-09 20:50:29 UTC

UBUNTU: SAUCE: x86: tsc: avoid system instability in hibernation

BugLink: https://bugs.launchpad.net/bugs/1913410

System instability are seen during resume from hibernation when system
is under heavy CPU load. This is due to the lack of update of sched
clock data, and the scheduler would then think that heavy CPU hog
tasks need more time in CPU, causing the system to freeze
during the unfreezing of tasks. For example, threaded irqs,
and kernel processes servicing network interface may be delayed
for several tens of seconds, causing the system to be unreachable.

Situation like this can be reported by using lockup detectors
such as workqueue lockup detectors:

[root@ip-172-31-67-114 ec2-user]# echo disk > /sys/power/state

Message from syslogd@ip-172-31-67-114 at May 7 18:23:21 ...
 kernel:BUG: workqueue lockup - pool cpus=0 node=0 flags=0x0 nice=0 stuck for 57s!

Message from syslogd@ip-172-31-67-114 at May 7 18:23:21 ...
 kernel:BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 57s!

Message from syslogd@ip-172-31-67-114 at May 7 18:23:21 ...
 kernel:BUG: workqueue lockup - pool cpus=3 node=0 flags=0x1 nice=0 stuck for 57s!

Message from syslogd@ip-172-31-67-114 at May 7 18:29:06 ...
 kernel:BUG: workqueue lockup - pool cpus=3 node=0 flags=0x1 nice=0 stuck for 403s!

The fix for this situation is to mark the sched clock as unstable
as early as possible in the resume path, leaving it unstable
for the duration of the resume process. This will force the
scheduler to attempt to align the sched clock across CPUs using
the delta with time of day, updating sched clock data. In a post
hibernation event, we can then mark the sched clock as stable
again, avoiding unnecessary syncs with time of day on systems
in which TSC is reliable.

Reviewed-by: Erik Quanstrom <quanstro@amazon.com>
Reviewed-by: Frank van der Linden <fllinden@amazon.com>
Reviewed-by: Balbir Singh <sblbir@amazon.com>
Reviewed-by: Munehisa Kamata <kamatam@amazon.com>
Tested-by: Anchal Agarwal <anchalag@amazon.com>
Signed-off-by: Eduardo Valentin <eduval@amazon.com>

CR: https://cr.amazon.com/r/8440112/
(cherry picked from aae9984b06c262e9bb9995c7015c940932307427 https://github.com/amazonlinux/linux.git)
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>

Author: Andrea Righi
Author Date: 2020-11-04 12:28:30 UTC

UBUNTU: test kernel 5.8.0-1011.11+arighi20201105

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>

Author: Andrea Righi
Author Date: 2020-11-04 16:33:00 UTC

UBUNTU: [Config] [aws] remove all sound-related modules

BugLink: https://bugs.launchpad.net/bugs/1902926

Sound modules are not needed in the AWS cloud.

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>

Author: Andrea Righi
Author Date: 2020-08-07 09:17:20 UTC

UBUNTU: test kernel 5.8.0-1001.1+arighi20200807

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>