在 2026/10/11 06:19, Waiman Long 写道:
> Before commit 103b08709e8a ("cgroup/cpuset: Fail if isolated and nohz_full
> don't leave any housekeeping"), the partition state can be freely switched
> from "root" to "isolated" and vice versa. After that commit, the switch
> from "root" to "isolated" can fail if it exhausts all the housekeeping
> CPUs. Later on, the switch from "isolated" to "root" can also fail if
> some of the partition CPUs are boot-time isolated by "isolcpus".
>
> A local or remote partition is made invalid when the switch fails.
> However there are 2 problems with the existing invalidation code.
>
> 1) Both the subpartitions_cpus and isolated_cpus are not properly
> updated.
> 2) In the case of remote partition with remote_partition flag set, it
> is not cleared.
>
> Fix this by calling the proper partition disabling function in this case.
>
> On an x86 test system with boot option "isolcpus=10 cgroup_debug" set
> and more than 16 cores, the following commands were executed after boot.
>
> # cd /sys/fs/cgroup
> # echo +cpuset > cgroup.subtree_control
> # cat cpuset.cpus.isolated
> 10
> # mkdir A
> # echo 10-12 > A/cpuset.cpus
> # echo isolated > A/cpuset.cpus.partition
> # cat A/cpuset.cpus.partition
> isolated
>
> Before the patch:
>
> # echo root > A/cpuset.cpus.partition
> # cat A/cpuset.cpus.partition
> root invalid (partition config conflicts with housekeeping setup)
> # cat cpuset.cpus.isolated .__DEBUG__.cpuset.cpus.subpartitions
> 10-12
> 10-12
>
> After the patch:
>
> # echo root > A/cpuset.cpus.partition
> # cat A/cpuset.cpus.partition
> root invalid (partition config conflicts with housekeeping setup)
> # cat cpuset.cpus.isolated .__DEBUG__.cpuset.cpus.subpartitions
> 10
>
> Reported-by: Tejun Heo <[email protected]>
> Link:
> https://lore.kernel.org/lkml/[email protected]/
> Fixes: 4a74e418881f ("cgroup/cpuset: Check partition conflict with
> housekeeping setup")
> Fixes: 103b08709e8a ("cgroup/cpuset: Fail if isolated and nohz_full don't
> leave any housekeeping")
> Signed-off-by: Waiman Long <[email protected]>
> ---
> kernel/cgroup/cpuset.c | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index fb41cd76add6..df1619d7a701 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -2863,6 +2863,7 @@ static int update_prstate(struct cpuset *cs, int
> new_prs)
> struct cpuset *parent = parent_cs(cs);
> struct tmpmasks tmpmask;
> bool isolcpus_updated = false;
> + bool disable_partition = false;
>
> if (old_prs == new_prs)
> return 0;
> @@ -2920,15 +2921,21 @@ static int update_prstate(struct cpuset *cs, int
> new_prs)
> */
> compute_excpus(cs, tmpmask.new_cpus);
> if (prstate_housekeeping_conflict(new_prs, parent_prs,
> - tmpmask.new_cpus, NULL))
> + tmpmask.new_cpus, NULL)) {
> + disable_partition = true;
> err = PERR_HKEEPING;
> - else
> + } else {
> isolcpus_updated = true;
> + }
> } else {
> /*
> * Switching back to member is always allowed even if it
> * disables child partitions.
> */
> + disable_partition = true;
> + }
> +
> + if (disable_partition) {
> if (is_remote_partition(cs))
> remote_partition_disable(cs, &tmpmask);
> else
> @@ -2937,7 +2944,7 @@ static int update_prstate(struct cpuset *cs, int
> new_prs)
>
> /*
> * Invalidation of child partitions will be done in
> - * update_cpumasks_hier().
> + * update_cpumasks_hier() below.
> */
> }
> out:
> @@ -2956,8 +2963,8 @@ static int update_prstate(struct cpuset *cs, int
> new_prs)
> isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus);
> spin_unlock_irq(&callback_lock);
>
> - /* Force update if switching back to member & update effective_xcpus */
> - update_cpumasks_hier(cs, &tmpmask, !new_prs);
> + /* Force update if partition is disabled & update effective_xcpus */
> + update_cpumasks_hier(cs, &tmpmask, disable_partition);
>
> /* A newly created partition must have effective_xcpus set */
> WARN_ON_ONCE(!old_prs && (new_prs > 0)
Reviewed-by: Guopeng Zhang <[email protected]>
Thanks,
Guopeng
