Re: [PATCH v8 08/21] tracing/remotes: Add dmesg tracefs file

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] tracing: trace_remote_do_dmesg() stalls iterator when
  !CONFIG_PRINTK
--

commit 8ec4000ae15e5140e201a48a2cd1db29b0828760
Author: Vincent Donnefort <vdonnefort@google.com>

tracing/remotes: Add dmesg tracefs file

This commit adds a dmesg tracefs file to trace remotes that redirects
remote trace events to dmesg when enabled.

> diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
> index 08a89b7315c3c..3dbb4912dbd6d 100644
> --- a/kernel/trace/trace_remote.c
> +++ b/kernel/trace/trace_remote.c

[ ... ]

> @@ -883,6 +909,87 @@ 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;
> +
> +		trace_remote_iter_move(iter);

[Severity: Low]
Does this stall the iterator when CONFIG_PRINTK is disabled?

With !CONFIG_PRINTK, the _printk() stub returns 0, so the loop breaks
before trace_remote_iter_move() consumes the peeked event.  Enabling the
dmesg file then keeps poll_work running and pins the remote trace buffer
open while repeatedly peeking the same first event without making progress.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261106180657.2460376-1-vdonnefort@google.com?part=8