Re: [PATCH] tracing: Export tracing_start() and tracing_stop()

From: Vincent Whitchurch
Date: Tue Jun 08 2021 - 08:59:32 EST

On Mon, Jun 07, 2021 at 03:14:32PM +0200, Steven Rostedt wrote:
> That said though, tracing_stop() is probably not what is wanted
> (unless its for a suspend to ram thing). According to the above
> description, the author really wants to use "tracing_off()" and not
> "tracing_stop()" as tracing_off() is faster and can be turned back on
> in user-space with the "tracing_on" file in tracefs, where as,
> tracing_stop() can not be. tracing_stop() needs a tracing_start() to
> get it going again.
> And tracing_off() is already EXPORT_SYMBOL_GPL() (as it is commonly
> used for debugging of modules). Again, it shouldn't have any in-kernel
> users in modules, because, like I stated above, it's similar to
> trace_printk() which should be removed before pushing to Linus.
> I'll NAK this patch for a different reason. Use tracing_off() instead.

Right, thanks, that's certainly much simpler. I'd only used
tracing_stop() before and never noticed that tracing_on can't be used to
restart tracing, probably because the kind of problems I used it for
usually resulted in the system needing a restart anyway to be usable.