linux-kernel - [PATCH tip/core/rcu 03/18] rcutorture: Refrain from callback flooding during boot

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Date:   Fri, 14 Feb 2020 16:36:56 -0800
From:   paulmck@...nel.org
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH tip/core/rcu 03/18] rcutorture: Refrain from callback flooding during boot

From: "Paul E. McKenney" <paulmck@...nel.org>

Additional rcutorture aggression can result in, believe it or not,
boot times in excess of three minutes on large hyperthreaded systems.
This is long enough for rcutorture to decide to do some callback flooding,
which seems a bit excessive given that userspace cannot have started
until long after boot, and it is userspace that does the real-world
callback flooding.  Worse yet, because Tiny RCU lacks forward-progress
functionality, the looping-in-the-kernel tests can also be problematic
during early boot.

This commit therefore causes rcutorture to hold off on callback
flooding until about the time that init is spawned, and the same
for looping-in-the-kernel tests for Tiny RCU.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/rcutorture.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 9ba4978..08fa4ef 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1994,8 +1994,11 @@ static int rcu_torture_fwd_prog(void *args)
 		schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
 		WRITE_ONCE(rcu_fwd_emergency_stop, false);
 		register_oom_notifier(&rcutorture_oom_nb);
-		rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
-		rcu_torture_fwd_prog_cr(rfp);
+		if (!IS_ENABLED(CONFIG_TINY_RCU) ||
+		    rcu_inkernel_boot_has_ended())
+			rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
+		if (rcu_inkernel_boot_has_ended())
+			rcu_torture_fwd_prog_cr(rfp);
 		unregister_oom_notifier(&rcutorture_oom_nb);

 		/* Avoid slow periods, better to test when busy. */
-- 
2.9.5