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From: "Michal Koutný" <mkoutny@suse.com>
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,  tj@kernel.org,
	lizefan.x@bytedance.com, hannes@cmpxchg.org,
	 yosryahmed@google.com, sinquersw@gmail.com,
	cgroups@vger.kernel.org,  bpf@vger.kernel.org
Subject: Re: [RFC PATCH bpf-next v2 2/9] cgroup: Eliminate the need for cgroup_mutex in proc_cgroup_show()
Date: Tue, 17 Oct 2023 16:04:04 +0200	[thread overview]
Message-ID: <ujaxujz3xczccobmiu2jxsstn3n7v4ly7vp72dqbgu5dyonrrw@nhzk7fhrpkkp> (raw)
In-Reply-To: <20231017124546.24608-3-laoar.shao@gmail.com>

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Hi.

I'd like this proc_cgroup_show de-contention.
(Provided the previous patch and this one can be worked out somehow.)

On Tue, Oct 17, 2023 at 12:45:39PM +0000, Yafang Shao <laoar.shao@gmail.com> wrote:
> They can ran successfully after implementing this change, with no RCU
> warnings in dmesg. It's worth noting that this change can also catch
> deleted cgroups, as demonstrated by running the following task at the
> same time:

Can those be other than v1 root cgroups? A suffix "(unmounted)" may be
more informative then.

(Non-zombie tasks prevent their cgroup removal, zombie tasks won't have
any non-trivial path rendered.)


> @@ -6256,7 +6256,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
>  	if (!buf)
>  		goto out;
>  
> -	cgroup_lock();
> +	rcu_read_lock();

What about the cgroup_path_ns_locked() that prints the path?

(I argue above that no non-trivial path is rendered but I'm not sure
whether rcu_read_lock() is sufficient sync wrt cgroup rmdir.)


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  reply	other threads:[~2023-10-17 14:04 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-17 12:45 [RFC PATCH bpf-next v2 0/9] bpf, cgroup: Add BPF support for cgroup1 hierarchy Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 1/9] cgroup: Make operations on the cgroup root_list RCU safe Yafang Shao
2023-10-17 13:20   ` Michal Koutný
2023-10-18  2:51     ` Yafang Shao
2023-10-18  9:35   ` Tejun Heo
2023-10-19  6:38     ` Yafang Shao
2023-10-19 19:08       ` Tejun Heo
2023-10-19 19:43         ` Waiman Long
2023-10-20  9:36           ` Yafang Shao
2023-10-20 17:51             ` Tejun Heo
2023-10-22  9:32               ` Yafang Shao
2023-10-25  8:06   ` kernel test robot
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 2/9] cgroup: Eliminate the need for cgroup_mutex in proc_cgroup_show() Yafang Shao
2023-10-17 14:04   ` Michal Koutný [this message]
2023-10-18  3:12     ` Yafang Shao
2023-10-18  9:38   ` Tejun Heo
2023-10-19  6:39     ` Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 3/9] cgroup: Add a new helper for cgroup1 hierarchy Yafang Shao
2023-10-18  9:44   ` Tejun Heo
2023-10-19  6:41     ` Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 4/9] bpf: Add a new kfunc " Yafang Shao
2023-10-18  9:40   ` Tejun Heo
2023-10-19  6:40     ` Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 5/9] selftests/bpf: Fix issues in setup_classid_environment() Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 6/9] selftests/bpf: Add parallel support for classid Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 7/9] selftests/bpf: Add a new cgroup helper get_classid_cgroup_id() Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 8/9] selftests/bpf: Add a new cgroup helper get_cgroup_hierarchy_id() Yafang Shao
2023-10-17 12:45 ` [RFC PATCH bpf-next v2 9/9] selftests/bpf: Add selftests for cgroup1 hierarchy Yafang Shao

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