ACK: [SRU][J][PATCH 0/1] kernel hard lockup in cgroups during eBPF workload

[Thibault Ferrante]

Acked-by: Thibault Ferrante <thibault.ferrante at canonical.com>


On 06-01-2025 23:15, Philip Cox wrote:
> 
> BugLink: https://bugs.launchpad.net/bugs/2089318
> 
> SRU Justification:
> 
> [Impact]
> 
> There is a kernel hard lockup where all CPUs are stuck acquiring an already-locked spinlock (css_set_lock) within the cgroup subsystem when the user is running a certain eBPF program.
> 
> This has been hit in focal 5.15 backport kernels.
> 
> [Fix]
> The bug was introduced in 5.15 via commit 74e4b956eb1c and fixed in 5.16 via 46307fd6e27a.
> 
> 
> [Test Plan]
> 
> This change has been tested by the LP user maxwolffe who opened the ticket and helped with the investigation.
> 
> 
> [Where problems could occur]
> 
> Due to the changes in the cgroup code between 5.15 and 5.16, the code was not a direct cherry-pick and had to be altered a bit.  This could cause issues in the future if there are further backports to the 5.15 kernel that touch the same area of the cgroup code.
> 
> --
> 
> Michal Koutný (1):
>    cgroup: Reorganize css_set_lock and kernfs path processing
> 
>   kernel/cgroup/cgroup.c | 86 ++++++++++++++++++++++++++++++------------
>   1 file changed, 62 insertions(+), 24 deletions(-)
>