[Bug 1864045] Re: [SRU] Hibernation events sometimes missed on repeated attempts

[Andrea Righi]

@rbalint unfortunately bisecting the kernel is not a trivial task...
there are many changes between the stock 4.15 and the 5.0 kernels and
the process is probably going to take a long time. I'll check if it's
possible to identify only a subset of potential commits that might have
caused this problem.

The steps that I've used to verify that the problem was fixed (or at
least it thought it was fixed) were pretty easy: I got acpid from
https://salsa.debian.org/debian/acpid.git (version 2.0.32-1), recompiled
it, moved it to /usr/sbin/acpid (replacing the stock 2.0.28) and then
tested multiple hibernate/resume cycles via the AWS APIs.

With this "custom" acpid I wasn't able to trigger any failure. It's also
worth mentioning that I was using 5.0.0-1019-aws. I'll repeat my tests
again with the latest bionic aws 5.0 kernel and will check if I can
reproduce the failures.

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Title:
  [SRU] Hibernation events sometimes missed on repeated attempts

Status in acpid package in Ubuntu:
  Confirmed
Status in linux package in Ubuntu:
  Incomplete
Status in acpid source package in Bionic:
  Incomplete
Status in linux source package in Bionic:
  Incomplete
Status in acpid source package in Eoan:
  Confirmed
Status in linux source package in Eoan:
  Incomplete

Bug description:
  When testing hibernation / resume on AWS with 5.0 or 5.3 kernels on
  bionic (using acpid 1:2.0.28-1ubuntu1), we sometimes see failure with
  repeated attempts. The first attempt will always be triggered, but the
  next attempt may not. The result is the agent never triggers the
  hibernation process and the instance will be forced to shutdown after
  a timeout period.

  Two workarounds have been identified. The first is to restart acpid
  during the resume handler. The second is to use the latest upstream
  acpid (as of Feb 1, 2020). This second workaround indicates there may
  be a patch missing in the acpid in bionic (1:2.0.28-1ubuntu1) to work
  with the 5.0+ kernels.

  To reproduce this problem:

  1) Launch an c4, c5, m4, m5, r4, r5 instance type with a 5.0 or 5.3 kernel on a bionic image with on-demand hibernation support enabled.
  2) Hibernate and resume the instance, ensuring the system is fully resumed afterward and the swap file has been removed.
  3) Hibernate and resume another time. The hibernate should be triggered immediately and the instance should become unresponsive as it saves state to disk.
  4) Resume the instance, it should come back with the same processes running.
  5) Repeat 3) - 4) as necessary.
  --- 
  ProblemType: Bug
  ApportVersion: 2.20.9-0ubuntu7.9
  Architecture: amd64
  DistroRelease: Ubuntu 18.04
  Ec2AMI: ami-0edf3b95e26a682df
  Ec2AMIManifest: (unknown)
  Ec2AvailabilityZone: us-west-2a
  Ec2InstanceType: m4.large
  Ec2Kernel: unavailable
  Ec2Ramdisk: unavailable
  Package: acpid 1:2.0.28-1ubuntu1
  PackageArchitecture: amd64
  ProcEnviron:
   TERM=screen
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=C.UTF-8
   SHELL=/bin/bash
  ProcVersionSignature: User Name 5.0.0-1025.28-aws 5.0.21
  Tags:  bionic ec2-images
  Uname: Linux 5.0.0-1025-aws x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm audio cdrom dialout dip floppy lxd netdev plugdev sudo video
  _MarkForUpload: True

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