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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: bpf <bpf@vger.kernel.org>,
	Network Development <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <kernel-team@fb.com>,
	"Paul E . McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH bpf 1/2] bpf: fix a rcu_sched stall issue with bpf task/task_file iterator
Date: Tue, 18 Aug 2020 10:06:47 -0700	[thread overview]
Message-ID: <CAADnVQL-2PKh8rzVWjCWCSSO6WkdhS+azFUtcLmNT=1Wj1hH+A@mail.gmail.com> (raw)
In-Reply-To: <20200818162408.836816-1-yhs@fb.com>

On Tue, Aug 18, 2020 at 9:24 AM Yonghong Song <yhs@fb.com> wrote:
> index f21b5e1e4540..885b14cab2c0 100644
> --- a/kernel/bpf/task_iter.c
> +++ b/kernel/bpf/task_iter.c
> @@ -27,6 +27,8 @@ static struct task_struct *task_seq_get_next(struct pid_namespace *ns,
>         struct task_struct *task = NULL;
>         struct pid *pid;
>
> +       cond_resched();
> +
>         rcu_read_lock();
>  retry:
>         pid = idr_get_next(&ns->idr, tid);
> @@ -137,6 +139,8 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info,
>         struct task_struct *curr_task;
>         int curr_fd = info->fd;
>
> +       cond_resched();
> +

Instead of adding it to every *seq_get_next() it probably should be in
bpf_seq_read().
If cond_resched() is needed in task_file_seq_get_next() it should
probably be after 'again:'.

  parent reply	other threads:[~2020-08-18 17:07 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-18 16:24 [PATCH bpf 0/2] bpf: two fixes for bpf task/task_file iterators Yonghong Song
2020-08-18 16:24 ` [PATCH bpf 1/2] bpf: fix a rcu_sched stall issue with bpf task/task_file iterator Yonghong Song
2020-08-18 16:48   ` Andrii Nakryiko
2020-08-18 17:07     ` Yonghong Song
2020-08-18 17:06   ` Alexei Starovoitov [this message]
2020-08-18 17:13     ` Yonghong Song
2020-08-18 16:24 ` [PATCH bpf 2/2] bpf: avoid visit same object multiple times Yonghong Song

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