Re: [PATCH 2/3][RFC] tracing: Add optional percpu buffers for trace_printk()

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 2011-10-10 at 15:04 +0200, Peter Zijlstra wrote:
> On Mon, 2011-10-10 at 08:37 -0400, Steven Rostedt wrote:
> 
> > This will make debugging some of my embedded boards difficult (the ones
> > where I have no way to add kernel command lines). If there's a problem
> > at boot up, I will have to modify the kernel to get this to print.
> > 
> > For those that don't know the tracing code, it will just simply break.
> > 
> > Unless you want me to keep the kconfig option that enables it
> > permanently. Then I could do this.
> 
> There's a fairly easy fix for that, initialize it at boot, and free once
> userspace it up and running if no trace_printk() came by.

Hmm, I could do that. Of course this will add a check for a global
variable in all trace_printks. I could make it a read_mostly variable,
as it only gets updated once, or even encapsulate the entire check with
a static_switch() :)


> 
> > I also expect tglx to throw frozen sharks at me for "why doesn't
> > trace_printk() work anymore?!!!!"
> 
> I'm sure you'll get over that :-)

I've had too many, I'm not sure my head could take much more.

-- Steve