Re: [PATCH v7 08/20] tracing/remotes: Add dmesg tracefs file

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] tracing: infinite polling loop when pr_info returns 0
--

commit 84b99572dcf19a3615c7c7c55a76f23735f8f5c9
Author: Vincent Donnefort <vdonnefort@google.com>

tracing/remotes: Add dmesg tracefs file

This commit introduces a dmesg tracefs file for the tracing remotes subsystem.
When enabled, it redirects all events to dmesg, acting similarly to tp_printk.

> diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
> --- a/kernel/trace/trace_remote.c
> +++ b/kernel/trace/trace_remote.c

[ ... ]

> @@ -883,6 +909,87 @@ static const struct file_operations trace_fops = {
> +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]
What happens here in trace_remote_do_dmesg() if the kernel is compiled with
CONFIG_PRINTK disabled?

When CONFIG_PRINTK=n, the pr_info() macro unconditionally returns 0. If
pr_info() returns 0, this loop breaks immediately before calling
trace_remote_iter_move() to consume the event.

Could this result in the same event being infinitely polled without making
progress, wedging the remote trace integration?

> +
> +		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/20260924145754.1285146-1-vdonnefort@google.com?part=8