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Date:   Wed, 15 Nov 2023 22:34:10 -0500
MIME-Version: 1.0
Subject: Re: [PATCH 2/3] bpf: bpf_iter_task_next: use __next_thread() rather
 than next_thread()
Content-Language: en-GB
To:     Oleg Nesterov <oleg@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>
Cc:     Chuyi Zhou <zhouchuyi@bytedance.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Kui-Feng Lee <kuifeng@fb.com>, linux-kernel@vger.kernel.org,
        bpf@vger.kernel.org
References: <20231114163237.GA897@redhat.com>
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From:   Yonghong Song <yonghong.song@linux.dev>
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On 11/14/23 11:32 AM, Oleg Nesterov wrote:
> Lockless use of next_thread() should be avoided, kernel/bpf/task_iter.c
> is the last user and the usage is wrong.
>
> bpf_iter_task_next() can loop forever, "kit->pos == kit->task" can never
> happen if kit->pos execs. Change this code to use __next_thread().
>
> With or without this change the usage of kit->pos/task and next_task()
> doesn't look nice, see the next patch.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Yonghong Song <yonghong.song@linux.dev>