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    SubjectRe: [PATCH tip/core/rcu 11/15] rcu: Avoid spurious RCU CPU stall warnings
    On Thu, Aug 30, 2012 at 11:56:24AM -0700, Paul E. McKenney wrote:
    > From: "Paul E. McKenney" <paul.mckenney@linaro.org>
    >
    > If a given CPU avoids the idle loop but also avoids starting a new
    > RCU grace period for a full minute, RCU can issue spurious RCU CPU
    > stall warnings. This commit fixes this issue by adding a check for
    > ongoing grace period to avoid these spurious stall warnings.
    >
    > Reported-by: Becky Bruce <bgillbruce@gmail.com>
    > Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
    > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

    Reviewed-by: Josh Triplett <josh@joshtriplett.org>

    > ---
    > kernel/rcutree.c | 3 ++-
    > 1 files changed, 2 insertions(+), 1 deletions(-)
    >
    > diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    > index fbe43b0..e58097b 100644
    > --- a/kernel/rcutree.c
    > +++ b/kernel/rcutree.c
    > @@ -820,7 +820,8 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
    > j = ACCESS_ONCE(jiffies);
    > js = ACCESS_ONCE(rsp->jiffies_stall);
    > rnp = rdp->mynode;
    > - if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
    > + if (rcu_gp_in_progress(rsp) &&
    > + (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
    >
    > /* We haven't checked in, so go dump stack. */
    > print_cpu_stall(rsp);
    > --
    > 1.7.8
    >


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