Re: [PATCH] dynamic debug: allow printing to trace event

[Steven Rostedt]

On Thu, 23 Jul 2020 12:57:35 +0200
Vincent Whitchurch <vincent.whitchurch@xxxxxxxx> wrote:

> Would it be acceptable to just use a fixed size for the event?  At least
> for my own debugging use cases it's preferable to just have to increase
> the trace buffer size in case it's insufficient, rather than to have to
> restort to one-off debugging code.

There's two other options.

Option 1, is to allocate 256 bytes times 4 (in case of interruption,
where you have a separate buffer for every context - normal, softirq,
irq, nmi), and use it like I do for stack traces in the latest kernel
(see __ftrace_stack_trace() in kernel/trace/trace.c)

Option 2, would be to use trace_array_vprintk(), but you need to create
your own instance to do so to keep from messing with the top level buffer.

-- Steve