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SubjectRe: [PATCH net 3/3] netdevsim: psp: rcu protect psp_dev reference
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On 5/6/26 3:34 PM, Willem de Bruijn wrote:
> Daniel Zahka wrote
>> static ssize_t
>> @@ -228,16 +237,23 @@ nsim_psp_rereg_write(struct file *file, const char __user *data, size_t count,
>> loff_t *ppos)
>> {
>> struct netdevsim *ns = file->private_data;
>> - int err;
>> + struct psp_dev *psd;
>> + ssize_t ret;
>>
>> mutex_lock(&ns->psp.rereg_lock);
>> - __nsim_psp_uninit(ns);
>> + __nsim_psp_uninit(ns, false);
>> +
>> + psd = psp_dev_create(ns->netdev, &nsim_psp_ops, &nsim_psp_caps, ns);
>> + if (IS_ERR(psd)) {
>> + ret = PTR_ERR(psd);
>> + goto out;
>> + }
> Do you want to create the new device first and only delete the old
> state if that succeeds? To avoid a netdevsim in state without dev.
>
>>
>> - ns->psp.dev = psp_dev_create(ns->netdev, &nsim_psp_ops,
>> - &nsim_psp_caps, ns);
>> - err = PTR_ERR_OR_ZERO(ns->psp.dev);
>> + rcu_assign_pointer(ns->psp.dev, psd);
>> + ret = count;
>> +out:
>> mutex_unlock(&ns->psp.rereg_lock);
>> - return err ?: count;
>> + return ret;
>> }
>>

Unfortunately, the way we have psp_dev_unregister() written, it would
clear out the main_netdev->psp_dev field from the second
psp_dev_create() call. I don't believe there is use case to do this in a
real driver, so I'm not sure we need to change how the create/unregister
paths work.



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