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Subject[PATCH RFC tip/core/rcu 09/28] rcu: Document failing tick as cause of RCU CPU stall warning
Date
One of lclaudio's systems was seeing RCU CPU stall warnings from idle.
These turned out to be caused by a bug that stopped scheduling-clock
tick interrupts from being sent to a given CPU for several hundred seconds.
This commit therefore updates the documentation to call this out as a
possible cause for RCU CPU stall warnings.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
Documentation/RCU/stallwarn.txt | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt
index 4e95920..f3e0625 100644
--- a/Documentation/RCU/stallwarn.txt
+++ b/Documentation/RCU/stallwarn.txt
@@ -101,6 +101,11 @@ o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that
CONFIG_TREE_PREEMPT_RCU case, you might see stall-warning
messages.

+o A hardware or software issue shuts off the scheduler-clock
+ interrupt on a CPU that is not in dyntick-idle mode. This
+ problem really has happened, and seems to be most likely to
+ result in RCU CPU stall warnings for CONFIG_NO_HZ=n kernels.
+
o A bug in the RCU implementation.

o A hardware failure. This is quite unlikely, but has occurred
--
1.7.3.2


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