[PATCH RFC tip/core/rcu 14/14] documentation: Describe new expedited stall warnings

Paul E. McKenney
2015-06-30T22:27:24Z

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
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1.8.1.5