Re: [PATCH v2 2/5] scftorture: Reject empty workloads before starting helpers

[Paul E. McKenney]

On Sun, Nov 08, 2026 at 07:02:38PM -0500, Joel Fernandes wrote:
> A module loaded with nthreads=0 starts its statistics task, but cleanup
> skips stopping that task. Unloading the module then leaves it executing
> freed module text. Reject a zero thread count before starting helpers;
> negative counts still select the online CPU count.
> 
> Also, when built as a module with reschedule-only, this leaves the
> selector empty because resched_cpu() is unavailable to modules. It warns
> while selecting an operation, invokes no callbacks, and can nevertheless
> report SUCCESS.  Reject an empty effective selector after filtering
> unsupported operations.
> 
> Both failures were reproduced in a guest without the patches.
> 
> Signed-off-by: Joel Fernandes <joelagnelf@xxxxxxxxxx>

Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxx>

If you wish, you could split this into two commits, but your call.

							Thanx, Paul

> ---
>  kernel/scftorture.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/kernel/scftorture.c b/kernel/scftorture.c
> index 603b2dba1536..ff9a8271a464 100644
> --- a/kernel/scftorture.c
> +++ b/kernel/scftorture.c
> @@ -588,6 +588,12 @@ static int __init scf_torture_init(void)
>  
>  	scftorture_print_module_parms("Start of test");
>  
> +	if (!nthreads) {
> +		SCFTORTOUT_ERRSTRING("nthreads must be nonzero");
> +		firsterr = -EINVAL;
> +		goto unwind;
> +	}
> +
>  	if (weight_resched <= 0 &&
>  	    weight_single <= 0 && weight_single_rpc <= 0 && weight_single_wait <= 0 &&
>  	    weight_many <= 0 && weight_many_wait <= 0 &&
> @@ -636,6 +642,11 @@ static int __init scf_torture_init(void)
>  	scf_sel_add(weight_many_wait1, SCF_PRIM_MANY, true);
>  	scf_sel_add(weight_all1, SCF_PRIM_ALL, false);
>  	scf_sel_add(weight_all_wait1, SCF_PRIM_ALL, true);
> +	if (!scf_sel_array_len) {
> +		SCFTORTOUT_ERRSTRING("no supported operations selected");
> +		firsterr = -EINVAL;
> +		goto unwind;
> +	}
>  	scf_sel_dump();
>  
>  	if (onoff_interval > 0) {
> -- 
> 2.54.0
>