From: Scott Wood <scottwood@freescale•com>
To: saikrishna gajula <saysai.gajula@gmail•com>
Cc: linuxppc-dev@lists•ozlabs.org
Subject: Re: PowerPC, P2020RDB, application debug when the application is in tight loop, Sysrq
Date: Wed, 1 May 2013 14:54:17 -0500 [thread overview]
Message-ID: <1367438057.29231.9@snotra> (raw)
In-Reply-To: <CAGstqXHrHWdiE=RvZ=1sV+=mPd9LiUZHL0gHPa89AVZRSND2Tg@mail.gmail.com> (from saysai.gajula@gmail.com on Wed Apr 17 00:04:10 2013)
On 04/17/2013 12:04:10 AM, saikrishna gajula wrote:
> HI All,
>=20
> I am new to this group. I am working on Freescale P2020
> platform running linux 2.6.21. I am looking for debug =20
> mechanism/utility,
> when a multi threaded application running on linux , appears to be =20
> hung (
> running in a tight loop,deadlock) while not able to access the board
> through serial/SSH/Telnet.
>=20
> I was looking at Magic sysrq option in linux to generate the stack,
> register dump when the application is hung. I am able to dump the call
> trace in normal working conditions. But i can't use echo t >
> /proc/sysrq-trigger and debug when the application hung.
>=20
> I am using below piece of code(drivers/serial/8250.c) on P2020RDB to =20
> debug
> the application where in , in hung situation, when i press 'y' =20
> followed by
> 't' on serial console it should go to sysrq handler, and dump the =20
> call
> trace, but it is not happening.(simply board hung)
>=20
> {
> if(sysrq_enable_flag)
> handle_sysrq(ch, up->port.info->tty);
>=20
> sysrq_enable_flag =3D 0;
>=20
> if(ch =3D=3D 'y')
> sysrq_enable_flag =3D 1;
> }
>=20
> It would be helpful if you provide any hint on the issue, or any =20
> other way
> to debug the application in hang situations.
There's an erratum regarding breaks in Freescale's serial port =20
implementation that has been worked around in more recent kernels. =20
2.6.21 is six years old. If you update to a kernel that has the =20
workaround, or backport the workaround yourself to your old kernel, you =20
should be able to use a break instead of hacking in a check for 'y'.
Other than that, either the kernel is hung too badly to respond to =20
serial input at all (in which case use JTAG to debug) or there's =20
something wrong with your 'y' hack (sysrq_enable_flag doesn't even =20
appear in current kernels so I can't see if this is the case without =20
digging through old code).
In any case, upgrade to a newer kernel -- maybe you're hitting a bug =20
that has been fixed since then.
-Scott=
next prev parent reply other threads:[~2013-05-01 19:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-17 5:04 PowerPC, P2020RDB, application debug when the application is in tight loop, Sysrq saikrishna gajula
2013-05-01 19:54 ` Scott Wood [this message]
2013-05-05 14:35 ` saikrishna gajula
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