Re: [PATCH v5 06/18] tracing/remotes: Add dmesg tracefs file

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] When CONFIG_PRINTK is disabled, dmesg redirection stalls the event iterator perpetually because `pr_info` returns 0.
--

--- Patch [6]: [PATCH v5 06/18] tracing/remotes: Add dmesg tracefs file ---
commit b41c280df86084ff7600dad9b61a6fa3dbbdf1dd
Author: Vincent Donnefort <[email protected]>

tracing/remotes: Add dmesg tracefs file

When enabled, the dmesg tracefs file enables the redirection of all
events to dmesg. This is similar to tp_printk.

> diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
> index 1fbe2f3f20e99..3a5e0d84c1722 100644
> --- a/kernel/trace/trace_remote.c
> +++ b/kernel/trace/trace_remote.c

[ ... ]

> @@ -882,6 +908,87 @@ static const struct file_operations trace_fops = {
>  	.release	= trace_release,
>  };
>  
> +static bool trace_remote_do_dmesg(struct trace_remote *remote)
> +{
> +	struct trace_remote_iterator *iter = smp_load_acquire(&remote->dmesg);
> +	unsigned int max_events = 1000;
> +
> +	if (!iter)
> +		return false;
> +
> +	trace_remote_iter_read_start(iter);
> +
> +	while (trace_remote_iter_read_event(iter)) {
> +		trace_seq_init(&iter->seq);
> +
> +		trace_remote_iter_print_event(iter);
> +		trace_seq_putc(&iter->seq, 0);
> +		if (!pr_info("%s", seq_buf_str(&iter->seq.seq)))
> +			break;

[Severity: Medium]
When CONFIG_PRINTK is disabled, pr_info() is defined as no_printk, which
unconditionally returns 0. Does this cause the loop to always break early
and skip the call to trace_remote_iter_move() below?

If so, it appears the background polling work would continually fail to drain
the trace remote buffer and run periodically without doing any work, as the
iterator never advances.

> +
> +		trace_remote_iter_move(iter);
> +
> +		if (!(--max_events))
> +			break;
> +	}
> +
> +	trace_remote_iter_read_finished(iter);
> +
> +	return !max_events;
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=6