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From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     rcu@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org,
        jiangshanlai@gmail.com, akpm@linux-foundation.org,
        mathieu.desnoyers@efficios.com, josh@joshtriplett.org,
        tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org,
        dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com,
        oleg@redhat.com, joel@joelfernandes.org,
        "Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 19/26] rcutorture: Make rcu_torture_boost_failed() check for GP end
Date:   Tue, 11 May 2021 16:12:16 -0700
Message-Id: <20210511231223.2895398-19-paulmck@kernel.org>
In-Reply-To: <20210511231149.GA2895263@paulmck-ThinkPad-P17-Gen-1>
References: <20210511231149.GA2895263@paulmck-ThinkPad-P17-Gen-1>
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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@kernel.org>
---
 kernel/rcu/rcutorture.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 31338b2d6609..02a14dfcae67 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
-- 
2.31.1.189.g2e36527f23