[Bug 1954676] Re: jammy 5.15 soft lockup when zfs.ko is loaded on s390x

[Andrea Righi]

** Also affects: gcc-11 (Ubuntu)
   Importance: Undecided
       Status: New

** Description changed:

  [Impact]
  
  Installing zfs-dkms seems to trigger a soft lockup issue as soon as
  zfs.ko is loaded. When the soft lockup happens the system isn't
  reachable anymore via ssh and on the console we can see some exlicit rcu
  stall warnings.
+ 
+ This seems to happen only when zfs is compile with gcc >=
+ 11.2.0-10ubuntu1. Downgrading gcc to previous versions doesn't show the
+ problem and zfs is working just fine.
  
  [Test case]
  
  On s390x install the latest 5.15 Jammy kernel and run:
  apt install zfs-dkms
  
  [Fix]
  
  Moving to zfs 2.1.1 (from Debian) seems to fix the problem.
  
  [Regression potential]
  
  It is a major zfs update so we may introduce zfs regressions, but it
  seems sane to be aligned with the upstream zfs version. Also the zfs
  smoke tests passed across all architectures, so moving to this new
  version seems the right thing to do.

** Description changed:

  [Impact]
  
  Installing zfs-dkms seems to trigger a soft lockup issue as soon as
  zfs.ko is loaded. When the soft lockup happens the system isn't
  reachable anymore via ssh and on the console we can see some exlicit rcu
  stall warnings.
  
  This seems to happen only when zfs is compile with gcc >=
  11.2.0-10ubuntu1. Downgrading gcc to previous versions doesn't show the
  problem and zfs is working just fine.
  
  [Test case]
  
  On s390x install the latest 5.15 Jammy kernel and run:
  apt install zfs-dkms
  
  [Fix]
  
- Moving to zfs 2.1.1 (from Debian) seems to fix the problem.
- 
- [Regression potential]
- 
- It is a major zfs update so we may introduce zfs regressions, but it
- seems sane to be aligned with the upstream zfs version. Also the zfs
- smoke tests passed across all architectures, so moving to this new
- version seems the right thing to do.
+ Temporary workaround is to downgrade gcc.

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https://bugs.launchpad.net/bugs/1954676

Title:
  jammy 5.15 kernel soft lockup when zfs.ko is loaded on s390x w/ gcc >=
  11.2.0-10ubuntu1

Status in gcc-11 package in Ubuntu:
  New
Status in zfs-linux package in Ubuntu:
  New
Status in gcc-11 source package in Jammy:
  New
Status in zfs-linux source package in Jammy:
  New

Bug description:
  [Impact]

  Installing zfs-dkms seems to trigger a soft lockup issue as soon as
  zfs.ko is loaded. When the soft lockup happens the system isn't
  reachable anymore via ssh and on the console we can see some exlicit
  rcu stall warnings.

  This seems to happen only when zfs is compile with gcc >=
  11.2.0-10ubuntu1. Downgrading gcc to previous versions doesn't show
  the problem and zfs is working just fine.

  [Test case]

  On s390x install the latest 5.15 Jammy kernel and run:
  apt install zfs-dkms

  [Fix]

  Temporary workaround is to downgrade gcc.

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