Commit 2c01531f authored by Paul E. McKenney's avatar Paul E. McKenney

rcu: Document failing tick as cause of RCU CPU stall warning

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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 91afaf30
...@@ -101,6 +101,11 @@ o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that ...@@ -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 CONFIG_TREE_PREEMPT_RCU case, you might see stall-warning
messages. 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 bug in the RCU implementation.
o A hardware failure. This is quite unlikely, but has occurred o A hardware failure. This is quite unlikely, but has occurred
......
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