Re: [PATCH v6 06/18] tracing/remotes: Add dmesg tracefs file

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Infinite loop/stuck iterator in `trace_remote_do_dmesg()` when `CONFIG_PRINTK` is disabled.
--

--- Patch [6]: [PATCH v6 06/18] tracing/remotes: Add dmesg tracefs file ---
commit dcbacd33ccf7193b3ba94b1298b0c78d75002d92
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 = {
> +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]
Does this cause an infinite loop if CONFIG_PRINTK is disabled?

When CONFIG_PRINTK is not set, pr_info() evaluates to 0. If that happens,
!pr_info() will always evaluate to true, causing the loop to break early
before trace_remote_iter_move() is called. 

Could this leave the iterator stuck on the same event indefinitely during
the next polling intervals?

> +
> +		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