Re: [RESEND][PATCH v15 2/4] perf: Support deferred user callchains

[Peter Zijlstra <peterz@infradead.org>]

On Mon, Sep 08, 2025 at 01:14:14PM -0400, Steven Rostedt wrote:
> +	/*
> +	 * All accesses related to the event are within the same RCU section in
> +	 * perf_event_callchain_deferred(). The RCU grace period before the
> +	 * event is freed will make sure all those accesses are complete by then.
> +	 */
> +	rcuwait_wait_event(&event->pending_unwind_wait, !event->pending_unwind_callback, TASK_UNINTERRUPTIBLE);

You need a narrower terminal, this is again excessive. I mostly code
with my screen split in 4 columns (3 if I can't find my glasses), and
that gets me around 90 character columns.

> +	if (event->attr.defer_callchain)
> +		init_task_work(&event->pending_unwind_work,
> +			       perf_event_callchain_deferred);

And let me hand you a bucket of {}, I've heard they're getting expensive
over in the US due to this tariff nonsense :-)