Re: [PATCH bpf-next v3 2/3] bpf: Add wakeup_source iterator

[bot+bpf-ci@kernel.org]

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> diff --git a/kernel/bpf/wakeup_source_iter.c b/kernel/bpf/wakeup_source_iter.c
> new file mode 100644
> index 000000000000..ab83d212a1f9
> --- /dev/null
> +++ b/kernel/bpf/wakeup_source_iter.c

[ ... ]

> +static void wakeup_source_iter_seq_stop(struct seq_file *seq, void *v)
> +{
> +	int *srcuidx = seq->private;
> +
> +	if (*srcuidx >= 0)
> +		wakeup_sources_read_unlock(*srcuidx);
> +	*srcuidx = -1;
> +}

Should this function call __wakeup_source_seq_show(seq, v, true) when v is
NULL to notify the BPF program that iteration has completed?

Looking at other BPF iterators like map_iter, prog_iter, link_iter,
task_iter, and kmem_cache_iter, they all invoke the BPF program with
in_stop=true when the stop callback receives a NULL pointer. For example,
map_iter does:

    static void bpf_map_seq_stop(struct seq_file *seq, void *v)
    {
        if (!v)
            (void)__bpf_map_seq_show(seq, v, true);
        ...
    }

The bpf_seq_read() function in kernel/bpf/bpf_iter.c has this comment at
the stop label: "/* bpf program called if !p */", which suggests this
callback is expected.

The __wakeup_source_seq_show() function already accepts an in_stop
parameter but is never called with true. Without this callback, BPF
programs using this iterator cannot detect when iteration has finished.


---
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