rcu: Add more debug info on "kthread starved" RCU CPU stall warnings

This commit adds grace number and command-flags information to the
"kthread starved" message that is sometimes printed out as part of
RCU CPU stall warnings.  This message is caused by the corresponding
RCU grace-period kthread not having run for at least two seconds, and
this added information can be helpful when debugging.

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

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7d369b8..52f064a 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1136,8 +1136,9 @@ static void rcu_check_gp_kthread_starvation(struct rcu_state *rsp)
        j = jiffies;
        gpa = READ_ONCE(rsp->gp_activity);
        if (j - gpa > 2 * HZ)
-               pr_err("%s kthread starved for %ld jiffies!\n",
-                      rsp->name, j - gpa);
+               pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x\n",
+                      rsp->name, j - gpa,
+                      rsp->gpnum, rsp->completed, rsp->gp_flags);
 }
 
 /*