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

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Message-id: <BN3PR0601MB14290AA17D24D0A20CFA8B85C8B90@BN3PR0601MB1429.namprd06.prod.outlook.com>
Date:	Sun, 28 Feb 2016 01:38:52 +0000
From:	SANKETH NALLI <nalli@...c.edu>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: tracing: Allow mmio tracer to display trace_printk() and other
 events

Hi Stephen,
I hope you are the correct person for this question.
https://lkml.org/lkml/2016/2/27/192
--
Sanketh Nalli
College of Letters and Sciences
University of Wisconsin - Madison

________________________________________
From: SANKETH NALLI
Sent: Saturday, February 27, 2016 2:30 PM
To: 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