From: Tejun Heo <tj@kernel.org>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com,
andrii@kernel.org, martin.lau@linux.dev, song@kernel.org,
yonghong.song@linux.dev, kpsingh@kernel.org, sdf@google.com,
haoluo@google.com, jolsa@kernel.org, lizefan.x@bytedance.com,
hannes@cmpxchg.org, bpf@vger.kernel.org, cgroups@vger.kernel.org
Subject: Re: [PATCH bpf-next 3/4] bpf: Add new kfunc bpf_cpumask_set_from_pid
Date: Sat, 23 Dec 2023 02:51:26 +0900 [thread overview]
Message-ID: <ZYXMns6PV1byBWtg@mac.lan> (raw)
In-Reply-To: <20231222113102.4148-4-laoar.shao@gmail.com>
Hello,
On Fri, Dec 22, 2023 at 11:31:01AM +0000, Yafang Shao wrote:
> Introducing a new kfunc: bpf_cpumask_set_from_pid. This function serves the
> purpose of retrieving the cpumask associated with a specific PID. Its
> utility is particularly evident within container environments. For
> instance, it allows for extracting the cpuset of a container using the
> init task within it.
>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
...
> +__bpf_kfunc bool bpf_cpumask_set_from_pid(struct cpumask *cpumask, u32 pid)
> +{
> + struct task_struct *task;
> +
> + if (!cpumask)
> + return false;
> +
> + task = get_pid_task(find_vpid(pid), PIDTYPE_PID);
> + if (!task)
> + return false;
> +
> + cpumask_copy(cpumask, task->cpus_ptr);
> + put_task_struct(task);
> + return true;
> +}
This seems awfully specific. Why is this necessary? Shouldn't the BPF prog
get the task and bpf_cpumask_copy() its ->cpus_ptr instead?
Thanks.
--
tejun
next prev parent reply other threads:[~2023-12-22 17:51 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-22 11:30 [PATCH bpf-next 0/4] bpf: Add bpf_iter_cpumask Yafang Shao
2023-12-22 11:30 ` [PATCH bpf-next 1/4] cgroup, psi: Init PSI of root cgroup to psi_system Yafang Shao
2023-12-22 17:47 ` Tejun Heo
2023-12-24 3:14 ` Yafang Shao
2023-12-22 23:49 ` kernel test robot
2023-12-23 7:26 ` kernel test robot
2023-12-22 11:31 ` [PATCH bpf-next 2/4] bpf: Add bpf_iter_cpumask kfuncs Yafang Shao
2024-01-02 22:13 ` Andrii Nakryiko
2024-01-04 2:30 ` Yafang Shao
2023-12-22 11:31 ` [PATCH bpf-next 3/4] bpf: Add new kfunc bpf_cpumask_set_from_pid Yafang Shao
2023-12-22 17:51 ` Tejun Heo [this message]
2023-12-24 3:05 ` Yafang Shao
2023-12-22 11:31 ` [PATCH bpf-next 4/4] selftests/bpf: Add selftests for cpumask iter Yafang Shao
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