On 5/29/25 11:58 AM, Ihor Solodrai wrote:
On 4/3/25 6:10 PM, JP Kobryn wrote:
This non-functional change serves as preparation for moving to
subsystem-based rstat trees. The base stats are not an actual subsystem,
but in future commits they will have exclusive rstat trees just as other
subsystems will.
Moving the base stat objects into a new struct allows the
cgroup_rstat_cpu
struct to become more compact since it now only contains the minimum
amount
of pointers needed for rstat participation. Subsystems will (in future
commits) make use of the compact cgroup_rstat_cpu struct while
avoiding the
memory overhead of the base stat objects which they will not use.
An instance of the new struct cgroup_rstat_base_cpu was placed on the
cgroup struct so it can retain ownership of these base stats common
to all
cgroups. A helper function was added for looking up the cpu-specific
base
stats of a given cgroup. Finally, initialization and variable names were
adjusted where applicable.
Signed-off-by: JP Kobryn <inwardvessel@xxxxxxxxx>
---
include/linux/cgroup-defs.h | 38 ++++++++++-------
kernel/cgroup/cgroup.c | 8 +++-
kernel/cgroup/rstat.c | 84 ++++++++++++++++++++++---------------
3 files changed, 79 insertions(+), 51 deletions(-)
Hi everyone.
BPF CI started failing after recent upstream merges (tip: 90b83efa6701).
I bisected the issue to this patch, see a log snippet below [1]:
##[error]#44/9 btf_tag/btf_type_tag_percpu_vmlinux_helper
load_btfs:PASS:could not load vmlinux BTF 0 nsec
test_btf_type_tag_vmlinux_percpu:PASS:btf_type_tag_percpu 0 nsec
libbpf: prog 'test_percpu_helper': BPF program load failed: -EACCES
libbpf: prog 'test_percpu_helper': -- BEGIN PROG LOAD LOG --
0: R1=ctx() R10=fp0
; int BPF_PROG(test_percpu_helper, struct cgroup *cgrp, const char
*path) @ btf_type_tag_percpu.c:58
0: (79) r1 = *(u64 *)(r1 +0)
func 'cgroup_mkdir' arg0 has btf_id 437 type STRUCT 'cgroup'
1: R1_w=trusted_ptr_cgroup()
; cpu = bpf_get_smp_processor_id(); @ btf_type_tag_percpu.c:63
1: (7b) *(u64 *)(r10 -8) = r1 ; R1_w=trusted_ptr_cgroup()
R10=fp0 fp-8_w=trusted_ptr_cgroup()
2: (85) call bpf_get_smp_processor_id#8 ;
R0_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=1,var_off=(0x0; 0x1))
3: (79) r1 = *(u64 *)(r10 -8) ; R1_w=trusted_ptr_cgroup()
R10=fp0 fp-8_w=trusted_ptr_cgroup()
; cgrp->self.rstat_cpu, cpu); @ btf_type_tag_percpu.c:65
4: (79) r1 = *(u64 *)(r1 +32) ;
R1_w=percpu_ptr_css_rstat_cpu()
; rstat = (struct cgroup_rstat_cpu *)bpf_per_cpu_ptr( @
btf_type_tag_percpu.c:64
5: (bc) w2 = w0 ;
R0_w=scalar(id=1,smin=smin32=0,smax=umax=smax32=umax32=1,var_off=(0x0;
0x1))
R2_w=scalar(id=1,smin=smin32=0,smax=umax=smax32=umax32=1,var_off=(0x0;
0x1))
6: (85) call bpf_per_cpu_ptr#153 ;
R0=ptr_or_null_css_rstat_cpu(id=2)
; if (rstat) { @ btf_type_tag_percpu.c:66
7: (15) if r0 == 0x0 goto pc+1 ; R0=ptr_css_rstat_cpu()
; *(volatile int *)rstat; @ btf_type_tag_percpu.c:68
8: (61) r1 = *(u32 *)(r0 +0)
cannot access ptr member updated_children with moff 0 in struct
css_rstat_cpu with off 0 size 4
processed 9 insns (limit 1000000) max_states_per_insn 0
total_states 1 peak_states 1 mark_read 1
-- END PROG LOAD LOG --
libbpf: prog 'test_percpu_helper': failed to load: -EACCES
libbpf: failed to load object 'btf_type_tag_percpu'
libbpf: failed to load BPF skeleton 'btf_type_tag_percpu': -EACCES
test_btf_type_tag_vmlinux_percpu:FAIL:btf_type_tag_percpu_helper
unexpected error: -13 (errno 13)
The test in question [2]:
SEC("tp_btf/cgroup_mkdir")
int BPF_PROG(test_percpu_helper, struct cgroup *cgrp, const char *path)
{
struct cgroup_rstat_cpu *rstat;
__u32 cpu;
cpu = bpf_get_smp_processor_id();
rstat = (struct cgroup_rstat_cpu
*)bpf_per_cpu_ptr(cgrp->rstat_cpu, cpu);
if (rstat) {
/* READ_ONCE */
*(volatile int *)rstat; // BPF verification fails here
}
return 0;
}
Any ideas about how to properly fix this?
The struct cgroup_rstat_cpu is renamed to css_rstat_cpu. Most likely the test needs
change. I will take a look.
Thanks.
[1]
https://github.com/kernel-patches/bpf/actions/runs/15316839796/job/43125242673
[2]
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/tools/testing/selftests/bpf/progs/btf_type_tag_percpu.c#n68
[...]
