[tip: core/rcu] locktorture: Ignore nreaders_stress if no readlock support

[tip-bot2 for Hou Tao]

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

Commit-ID:     e5ace37d83af459bd491847df570b6763c602344
Gitweb:        https://git.kernel.org/tip/e5ace37d83af459bd491847df570b6763c602344
Author:        Hou Tao <houtao1@xxxxxxxxxx>
AuthorDate:    Fri, 18 Sep 2020 19:44:24 +08:00
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Fri, 06 Nov 2020 17:13:52 -08:00

locktorture: Ignore nreaders_stress if no readlock support

Exclusive locks do not have readlock support, which means that a
locktorture run with the following module parameters will do nothing:

 torture_type=mutex_lock nwriters_stress=0 nreaders_stress=1

This commit therefore rejects this combination for exclusive locks by
returning -EINVAL during module init.

Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 kernel/locking/locktorture.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 316531d..046ea2d 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -870,7 +870,8 @@ static int __init lock_torture_init(void)
 		goto unwind;
 	}
 
-	if (nwriters_stress == 0 && nreaders_stress == 0) {
+	if (nwriters_stress == 0 &&
+	    (!cxt.cur_ops->readlock || nreaders_stress == 0)) {
 		pr_alert("lock-torture: must run at least one locking thread\n");
 		firsterr = -EINVAL;
 		goto unwind;