Re: [PATCH v2 1/2] locktorture: doesn't check nreaders_stress when no readlock support

From: Paul E. McKenney
Date: Fri Sep 18 2020 - 13:59:14 EST

On Fri, Sep 18, 2020 at 07:44:24PM +0800, Hou Tao wrote:
> When do locktorture for exclusive lock which doesn't have readlock
> support, the following module parameters will be considered as valid:
> torture_type=mutex_lock nwriters_stress=0 nreaders_stress=1
> But locktorture will do nothing useful, so instead of permitting
> these useless parameters, let's reject these parameters by returning
> -EINVAL during module init.
> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>

Much better, much easier for people a year from now to understand.
Queued for v5.11, thank you!

I did edit the commit log a bit as shown below, so please let me
know if I messed anything up.

Thanx, Paul

commit 4985c52e3b5237666265e59f56856f485ee36e71
Author: Hou Tao <houtao1@xxxxxxxxxx>
Date: Fri Sep 18 19:44:24 2020 +0800

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>

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;