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SubjectRe: [RESEND PATCH bpf-next v6 8/8] selftests/bpf: Add tests for open-coded task and css iter
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Hello,

在 2023/10/20 08:03, Alexei Starovoitov 写道:
> On Tue, Oct 17, 2023 at 11:18 PM Chuyi Zhou <zhouchuyi@bytedance.com> wrote:
>>
>> +
>> +SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
>> +__failure __msg("css_task_iter is only allowed in bpf_lsm and bpf iter-s")
>> +int BPF_PROG(iter_css_task_for_each)
>> +{
>> + u64 cg_id = bpf_get_current_cgroup_id();
>> + struct cgroup *cgrp = bpf_cgroup_from_id(cg_id);
>> + struct cgroup_subsys_state *css;
>> + struct task_struct *task;
>> +
>> + if (cgrp == NULL)
>> + return 0;
>> + css = &cgrp->self;
>> +
>> + bpf_for_each(css_task, task, css, CSS_TASK_ITER_PROCS) {
>> +
>> + }
>> + bpf_cgroup_release(cgrp);
>> + return 0;
>> +}
>
> I think we should relax allowlist in patch 2 further.
> Any sleepable is safe.
> Allowlist is needed to avoid dead locking on css_set_lock.
> Any lsm and any iter (even non-sleepable) and any sleepable
> seems to be safe.
>
> Then the above test would need s/fentry.s/fentry/ to stay relevant.
>
> I would also add:
>
> SEC("iter/cgroup")
> int cgroup_id_printer(struct bpf_iter__cgroup *ctx)
> {
> struct seq_file *seq = ctx->meta->seq;
> struct cgroup *cgrp = ctx->cgroup;
>
> /* epilogue */
> if (cgrp == NULL) ..
>
> bpf_for_each(css_task, task, css, CSS_TASK_ITER_PROCS) {
> BPF_SEQ_PRINTF(); // something about task
> }
>
> To demonstrate how new kfunc iter can be combined with cgroup iter and
> it won't deadlock, though cgroup iter is not sleepable.
>

OK.

> I've applied the current set. Pls send a follow up. Thanks


I would try to send a follow up patch next week.

Thank.

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