lkml.org 
[lkml]   [2012]   [Sep]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: rcu self-detected stall messages on OMAP3, 4 boards
    On Sat, Sep 22, 2012 at 05:45:12PM +0200, Frederic Weisbecker wrote:
    > 2012/9/22 Paul E. McKenney <paulmck@linux.vnet.ibm.com>:
    > > On Fri, Sep 21, 2012 at 01:31:49PM -0700, Tony Lindgren wrote:
    > >> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> [120921 12:58]:
    > >> >
    > >> > Just to make sure I understand the combinations:
    > >> >
    > >> > o All stalls have happened when running a minimal userspace.
    > >> > o CONFIG_NO_HZ=n suppresses the stalls.
    > >> > o CONFIG_RCU_FAST_NO_HZ (which depends on CONFIG_NO_HZ=y) has
    > >> > no observable effect on the stalls.
    > >>
    > >> The reason why you may need minimal userspace is to cut down
    > >> the number of timers waking up the system with NO_HZ.
    > >> Booting with init=/bin/sh might also do the trick for that.
    > >
    > > Good point! This does make for a very quiet system, but does not
    > > reproduce the problem under kvm, even after waiting for four minutes.
    > > I will leave it for more time, but it looks like I really might need to
    > > ask Linaro for remote access to a Panda.
    >
    > I have one. I'm currently installing Ubuntu on it and I'll try to
    > manage to build
    > a kernel and reproduce the issue.
    >
    > I'll give more news soon.

    Thank you!

    My bet is that you have to have a userspace that is so small that it
    registers only a few (but at least one!) RCU callback at boot time,
    then never registers any callbacks ever again. I have coded up a
    crude test case, using Tony Lindgren's suggestion of "init=/bin/sh",
    but I appear to have inadvertently fixed this bug in current -rcu
    (git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git,
    branch rcu/next).

    But I have been wrong a few times already on this particular bug...

    Thanx, Paul



    \
     
     \ /
      Last update: 2012-09-22 18:41    [W:0.030 / U:2.260 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site