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[rcu,v2,08/10] rcutorture: Create nocb kthreads only when testing rcu in CONFIG_RCU_NOCB_CPU=y kernels

Message ID 20230323043935.1221184-9-boqun.feng@gmail.com (mailing list archive)
State Accepted
Commit 4f02ac237813a31d4fcb4c9eb9b699b15956b53b
Headers show
Series RCU torture test and tool updates for v6.4 | expand

Commit Message

Boqun Feng March 23, 2023, 4:39 a.m. UTC 
From: Zqiang <qiang1.zhang@intel.com>

Given a non-zero rcutorture.nocbs_nthreads module parameter, the specified
number of nocb kthreads will be created, regardless of whether or not
the RCU implementation under test is capable of offloading callbacks.
Please note that even vanilla RCU is incapable of offloading in kernels
built with CONFIG_RCU_NOCB_CPU=n.  And when the RCU implementation is
incapable of offloading callbacks, there is no point in creating those
kthreads.

This commit therefore checks the cur_ops.torture_type module parameter and
CONFIG_RCU_NOCB_CPU Kconfig option in order to avoid creating unnecessary
nocb tasks.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[ boqun: Fix checkpatch warning ]
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
 kernel/rcu/rcutorture.c | 6 ++++++
 1 file changed, 6 insertions(+)
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Patch

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index c0b2fd687bbb..e046d2c6fe10 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -3525,6 +3525,12 @@  rcu_torture_init(void)
 		pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
 		fqs_duration = 0;
 	}
+	if (nocbs_nthreads != 0 && (cur_ops != &rcu_ops ||
+				    !IS_ENABLED(CONFIG_RCU_NOCB_CPU))) {
+		pr_alert("rcu-torture types: %s and CONFIG_RCU_NOCB_CPU=%d, nocb toggle disabled.\n",
+			 cur_ops->name, IS_ENABLED(CONFIG_RCU_NOCB_CPU));
+		nocbs_nthreads = 0;
+	}
 	if (cur_ops->init)
 		cur_ops->init();