linux-kernel - Re: [PATCH v2 1/2] locktorture: doesn't check nreaders

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Date:   Sat, 19 Sep 2020 11:25:45 +0800
From:   Hou Tao <houtao1@...wei.com>
To:     <paulmck@...nel.org>
CC:     Josh Triplett <josh@...htriplett.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        <linux-kernel@...r.kernel.org>, <rcu@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] locktorture: doesn't check nreaders_stress when no
 readlock support

Hi Paul,

On 2020/9/19 1:59, Paul E. McKenney wrote:
> 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@...wei.com>
> 
> 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.
> 
Thanks for your edit, it looks more clearer.

Regards,
Tao
> 							Thanx, Paul
> 
> commit 4985c52e3b5237666265e59f56856f485ee36e71
> Author: Hou Tao <houtao1@...wei.com>
> 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@...wei.com>
>     Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> 
> 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;
> .
>