rcu: Diagnostics for grace-period startup hangs
This commit causes a splat if RCU is idle and a request for a new grace
period is ignored for more than one second. This splat normally indicates
that some code path asked for a new grace period, but failed to wake up
the RCU grace-period kthread.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Fix bug located by Dan Carpenter and his static checker. ]
[ paulmck: Fix self-deadlock bug located 0day test robot. ]
[ paulmck: Disable unless CONFIG_PROVE_RCU=y. ]
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 7365ac5..3c19421 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -374,6 +374,8 @@ struct rcu_state {
/* but in jiffies. */
unsigned long gp_activity; /* Time of last GP kthread */
/* activity in jiffies. */
+ unsigned long gp_req_activity; /* Time of last GP request */
+ /* in jiffies. */
unsigned long jiffies_stall; /* Time at which to check */
/* for CPU stalls. */
unsigned long jiffies_resched; /* Time at which to resched */