[tip: core/rcu] rcutorture: Make rcu_torture_boost_failed() check for GP end

[tip-bot2 for Paul E. McKenney]

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     bcd4af44e2f173074328980b60178fdbb1853e4f
Gitweb:        https://git.kernel.org/tip/bcd4af44e2f173074328980b60178fdbb1853e4f
Author:        Paul E. McKenney <paulmck@xxxxxxxxxx>
AuthorDate:    Thu, 08 Apr 2021 10:46:55 -07:00
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Mon, 10 May 2021 16:05:06 -07:00

rcutorture: Make rcu_torture_boost_failed() check for GP end

It is possible that a delayed grace period that rcu_torture_boost()
was polling for ended while rcu_torture_boost_failed() was printing the
failure splat.  It would be good to know when this happens.  This commit
therefore has rcu_torture_boost_failed() recheck the grace period after
printing the splat, and printing a message indicating whether or not
the grace period has ended.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 kernel/rcu/rcutorture.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 31338b2..02a14df 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -919,6 +919,7 @@ static void rcu_torture_enable_rt_throttle(void)
 static bool rcu_torture_boost_failed(unsigned long gp_state, unsigned long start, unsigned long end)
 {
 	static int dbg_done;
+	bool gp_done;
 
 	if (end - start > test_boost_duration * HZ - HZ / 2) {
 		// Recheck after checking time to avoid false positives.
@@ -931,6 +932,11 @@ static bool rcu_torture_boost_failed(unsigned long gp_state, unsigned long start
 			pr_info("Boost inversion thread ->rt_priority %u gp_state %lu jiffies %lu\n",
 				current->rt_priority, gp_state, end - start);
 			cur_ops->gp_kthread_dbg();
+			// Recheck after print to flag grace period ending during splat.
+			gp_done = cur_ops->poll_gp_state(gp_state);
+			pr_info("Boost inversion: GP %lu %s.\n", gp_state,
+				gp_done ? "ended already" : "still pending");
+
 		}
 
 		return true; // failed