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documentation: Describe new expedited stall warnings

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Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Paul E. McKenney 2015-06-30 14:54:09 -07:00
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Documentation/RCU/stallwarn.txt
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@ -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