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    SubjectRe: rcu self-detected stall messages on OMAP3, 4 boards
    Hi Paul

    On Sat, 22 Sep 2012, Paul E. McKenney wrote:

    > Strangely enough, I believe that I have inadvertently fixed this in
    > my -rcu tree:
    > git:// rcu/next
    > Nevertheless, if you get a chance to try it, I would be interested to
    > hear if my guess is correct.

    Yes, good news: the stall warnings go away with that branch.

    > The trick is that a kthread drives the grace period in -rcu, regardless
    > of whether or not there are callbacks.

    This is "rcu: Move quiescent-state forcing into kthread" ?

    Added some debugging into rcu_gp_kthread() after that commit and can
    confirm that the quiescent-state forcing loop does start a few times when
    there are zero callbacks pending (modulo any races in my measurement

    > However, the backport would not be something that -stable would be happy
    > with, so I will be putting together a fix for mainline. This thing
    > has been in the kernel since about 2004, not sure why you didn't hit
    > it earlier.

    One other data point in that regard - noticed the warnings don't appear
    when the board is booted with:

    commit 4fa3b6cb1bc8c14b81b4c8ffdfd3f2500a7e9367
    Author: Paul E. McKenney <>
    Date: Tue Jun 5 15:53:53 2012 -0700

    rcu: Fix qlen_lazy breakage


    - Paul

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