ACK: [SRU][J][PATCH 0/5][v5] kernel hard lockup in cgroups during eBPF workload

[Kuba Pawlak]

On 7.03.2025 20:16, 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.
>
> I have also run the cgroup selftests on this kernel to test it.
>
>
> [Where problems could occur]
>
> Further upstream stable changes to the cgroup code may cause merge conflicts, but this should be mitigated as I indent to try to upstream these changes to the upstream stable kernel.
>
>
> v2: added prerequisite commits
> v3: Added more prerequisite commits to reduce context changes
> v4: change to patches 2/5 and 5/5 due to code review comments
> v5: adjusted patch [5/5] for code review comments, and added buglinks to all commit messages
>
> --
>
> Lin Feng (1):
>    cgroup.c: add helper __cset_cgroup_from_root to cleanup duplicated
>      codes
>
> Michal Koutný (3):
>    cgroup: cgroup: Honor caller's cgroup NS when resolving cgroup id
>    cgroup: Homogenize cgroup_get_from_id() return value
>    cgroup: Reorganize css_set_lock and kernfs path processing
>
> Tejun Heo (1):
>    cgroup: Make cgroup_get_from_id() prettier
>
>   include/linux/blk-cgroup.h |   4 +-
>   include/linux/cgroup.h     |   5 --
>   kernel/cgroup/cgroup.c     | 111 ++++++++++++++++++++++---------------
>   3 files changed, 69 insertions(+), 51 deletions(-)
>
Acked-by: Kuba Pawlak <kuba.pawlak at canonical.com>
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