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    Subject[PATCH tip/core/rcu 16/19] documentation: Describe new expedited stall warnings
    Date
    From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    Documentation/RCU/stallwarn.txt | 17 +++++++++++++++++
    1 file changed, 17 insertions(+)

    diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
    index 046f32637b95..efb9454875ab 100644
    --- a/Documentation/RCU/stallwarn.txt
    +++ b/Documentation/RCU/stallwarn.txt
    @@ -163,6 +163,23 @@ message will be about three times the interval between the beginning
    of the stall and the first message.


    +Stall Warnings for Expedited Grace Periods
    +
    +If an expedited grace period detects a stall, it will place a message
    +like the following in dmesg:
    +
    + INFO: rcu_sched detected expedited stalls on CPUs: { 1 2 6 } 26009 jiffies s: 1043
    +
    +This indicates that CPUs 1, 2, and 6 have failed to respond to a
    +reschedule IPI, that the expedited grace period has been going on for
    +26,009 jiffies, and that the expedited grace-period sequence counter is
    +1043. The fact that this last value is odd indicates that an expedited
    +grace period is in flight.
    +
    +It is entirely possible to see stall warnings from normal and from
    +expedited grace periods at about the same time from the same run.
    +
    +
    What Causes RCU CPU Stall Warnings?

    So your kernel printed an RCU CPU stall warning. The next question is
    --
    1.8.1.5


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