rcu: Provide more diagnostics for stalled GP kthread

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

1 files changed, 8 insertions, 2 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 65137bc28b2b..1c58cbd03922 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1178,9 +1178,11 @@ 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! g%lu c%lu f%#x\n",
+                pr_err("%s kthread starved for %ld jiffies! g%lu c%lu f%#x s%d ->state=%#lx\n",
                        rsp->name, j - gpa,
-                       rsp->gpnum, rsp->completed, rsp->gp_flags);
+                       rsp->gpnum, rsp->completed,
+                       rsp->gp_flags, rsp->gp_state,
+                       rsp->gp_kthread ? rsp->gp_kthread->state : 0);
 }
 
 /*
@@ -2041,6 +2043,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
                         wait_event_interruptible(rsp->gp_wq,
                                                  READ_ONCE(rsp->gp_flags) &
                                                  RCU_GP_FLAG_INIT);
+                        rsp->gp_state = RCU_GP_DONE_GPS;
                         /* Locking provides needed memory barrier. */
                         if (rcu_gp_init(rsp))
                                 break;
@@ -2073,6 +2076,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
                                         (!READ_ONCE(rnp->qsmask) &&
                                          !rcu_preempt_blocked_readers_cgp(rnp)),
                                         j);
+                        rsp->gp_state = RCU_GP_DONE_FQS;
                         /* Locking provides needed memory barriers. */
                         /* If grace period done, leave loop. */
                         if (!READ_ONCE(rnp->qsmask) &&
@@ -2110,7 +2114,9 @@ static int __noreturn rcu_gp_kthread(void *arg)
                 }
 
                 /* Handle grace-period end. */
+                rsp->gp_state = RCU_GP_CLEANUP;
                 rcu_gp_cleanup(rsp);
+                rsp->gp_state = RCU_GP_CLEANED;
         }
 }