rcu: Print scheduling-clock information on RCU CPU stall-warning messages

There have been situations where RCU CPU stall warnings were caused by
issues in scheduling-clock timer initialization.  To make it easier to
track these down, this commit causes the RCU CPU stall-warning messages
to print out the number of scheduling-clock interrupts taken in the
current grace period for each stalled CPU.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 3cc419d05f2f..d27a2aa3e815 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -927,6 +927,20 @@ config RCU_CPU_STALL_VERBOSE
 
           Say Y if you want to enable such checks.
 
+config RCU_CPU_STALL_INFO
+        bool "Print additional diagnostics on RCU CPU stall"
+        depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
+        default n
+        help
+          For each stalled CPU that is aware of the current RCU grace
+          period, print out additional per-CPU diagnostic information
+          regarding scheduling-clock ticks, idle state, and,
+          for RCU_FAST_NO_HZ kernels, idle-entry state.
+
+          Say N if you are unsure.
+
+          Say Y if you want to enable such diagnostics.
+
 config RCU_TRACE
         bool "Enable tracing for RCU"
         depends on DEBUG_KERNEL