linux-kernel - Re: Soft lockup in rt2x00usb_work

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Date:   Wed, 8 Nov 2017 11:37:30 +0100
From:   Stanislaw Gruszka <sgruszka@...hat.com>
To:     Richard Genoud <richard.genoud@...il.com>
Cc:     Helmut Schaa <helmut.schaa@...glemail.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-wireless@...r.kernel.org
Subject: Re: Soft lockup in rt2x00usb_work_rxdone()

On Tue, Nov 07, 2017 at 12:01:23PM +0100, Richard Genoud wrote:
> Le mardi 07 novembre 2017 à 11:13 +0100, Stanislaw Gruszka a écrit :
> > On Tue, Nov 07, 2017 at 11:06:39AM +0100, Richard Genoud wrote:
> > > > 3 short articles how to configure and use ftrace are here:
> > > > https://lwn.net/Articles/365835/
> > > > https://lwn.net/Articles/366796/
> > > > https://lwn.net/Articles/370423/
> > > > 
> > > 
> > > I tried with ftrace, but I don't think there's a way to dump the
> > > trace
> > > when there's a soft lock-up
> > > (I can't do anything after the unbind, even the heartbeat led
> > > stopped blinking).
> > > I saw the /proc/sys/kernel/ftrace_dump_on_oops file, but there's no
> > > /proc/sys/kernel/ftrace_dump_on_soft_lock-up file :)
> > 
> > You should configure function trace with rt2x* functions. After that
> > start tracing, unbind the device, then stop tracing and provide trace
> > output.
> Ok, I found a way to display the trace (after the unbind, the board is
> frozen and I can't type anything).
> Adding
> CONFIG_SOFTLOCKUP_DETECTOR=y
> CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC=y
> along with echo 1 > /proc/sys/kernel/ftrace_dump_on_oops does the trick

No, that not I wanted you to do. Please remove those options and just do
below on tracing directory.

echo 0 > tracing_on 
cat trace >  /dev/null
echo "function_graph" > current_tracer 
echo "rt2*" > set_ftrace_filter 
echo 1 > tracing_on
echo 1-2.2 > /sys/bus/usb/drivers/usb/unbind
echo 0 > tracing_on
cat trace > ~/trace.txt

and provide trace.txt to me (can be in private email if big).

Thanks
Stanislaw