linux-kernel - tracing: Allow mmio tracer to display trace

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Message-id: <BN3PR0601MB1429A05BA8D900B0D716381EC8B80@BN3PR0601MB1429.namprd06.prod.outlook.com>
Date:	Sat, 27 Feb 2016 20:30:49 +0000
From:	SANKETH NALLI <nalli@...c.edu>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: tracing: Allow mmio tracer to display trace_printk() and other events

Hi,

I am trying to print trace markers from inside the kernel using the mmio-tracer's 
mmiotrace_printk routine but it doesn't get printed.  Looking back, i found this thread
and applied the said patch but that didn't work either.

https://lkml.org/lkml/2010/5/4/465

Thereafter, I followed the code path starting at mmiotrace_printk which lead to __trace_array_vprintk
and in there, 

       tbuffer = get_trace_buf();
        if (!tbuffer) {
             /*   pr_info("invalid buffer.\n"); */
                len = 0;
                goto out;
        }

tbuffer turns out to be null which is why the call to mmiotrace_printk returns without printing my marker.

Has this been fixed or looked into ? Any help would be much appreciated.
Thanks.

--
Sanketh Nalli
College of Letters and Sciences
University of Wisconsin - Madison