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, 11 insertions, 0 deletions

diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 0328a537846a..e2ac8ee415bb 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -239,6 +239,12 @@ struct rcu_data {
         bool            preemptible;    /* Preemptible RCU? */
         struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
         unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
+#ifdef CONFIG_RCU_CPU_STALL_INFO
+        unsigned long   ticks_this_gp;  /* The number of scheduling-clock */
+                                        /*  ticks this CPU has handled */
+                                        /*  during and after the last grace */
+                                        /* period it is aware of. */
+#endif /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
 
         /* 2) batch handling */
         /*
@@ -466,5 +472,10 @@ static void __cpuinit rcu_prepare_kthreads(int cpu);
 static void rcu_prepare_for_idle_init(int cpu);
 static void rcu_cleanup_after_idle(int cpu);
 static void rcu_prepare_for_idle(int cpu);
+static void print_cpu_stall_info_begin(void);
+static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
+static void print_cpu_stall_info_end(void);
+static void zero_cpu_stall_ticks(struct rcu_data *rdp);
+static void increment_cpu_stall_ticks(void);
 
 #endif /* #ifndef RCU_TREE_NONCORE */