Commit 99a930b0 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

documentation: Describe new expedited stall warnings 



Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent cf3620a6

Documentation/RCU/stallwarn.txt

+17 −0
Original line number Diff line number Diff line
@@ -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