linux-kernel - Re: [PATCH v8 2/5] usb: early: add driver for xhci debug capability

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Date:   Wed, 31 May 2017 02:24:39 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Vlastimil Babka <vbabka.lkml@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        tglx@...utronix.de, peterz@...radead.org,
        linux-usb@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 2/5] usb: early: add driver for xhci debug capability

On Wed, 31 May 2017 11:27:19 +0800
Lu Baolu <baolu.lu@...ux.intel.com> wrote:

  
> >> +
> >> +#define XDBC_TRACE
> >> +#ifdef XDBC_TRACE
> >> +#define	xdbc_trace	trace_printk  
> > Did you forget to remove the #define XDBC_TRACE?
> >
> > Enabling this driver brings the "trace_printk() being used.
> > Allocating extra memory. This means that this is a DEBUG kernel and
> > it is unsafe for production use." message in 4.12-rcX dmesg.  
> 
> This feature is only for a DEBUG kernel, should not be enabled for
> any production kernel. This was the reason I enabled trace_printk()
> by default.

Yes, it is perfectly fine to use trace_printk() for debug only configs.
But if if you have it there and it is helpful to debug something that
happens in a production system, you may want to look into creating a
real tracepoint for the locations.

-- Steve