Re: [PATCH v8 1/5] soc: qcom: pdr: protect locator_addr with the main mutex

[Dmitry Baryshkov]

On Thu, 6 Jun 2024 at 01:48, Chris Lew <quic_clew@xxxxxxxxxxx> wrote:
>
> Hi Dmitry,
>
> On 5/11/2024 2:56 PM, Dmitry Baryshkov wrote:
> ...
> > @@ -76,12 +76,12 @@ static int pdr_locator_new_server(struct qmi_handle *qmi,
> >                                             locator_hdl);
> >       struct pdr_service *pds;
> >
> > +     mutex_lock(&pdr->lock);
> >       /* Create a local client port for QMI communication */
> >       pdr->locator_addr.sq_family = AF_QIPCRTR;
> >       pdr->locator_addr.sq_node = svc->node;
> >       pdr->locator_addr.sq_port = svc->port;
> >
> > -     mutex_lock(&pdr->lock);
> >       pdr->locator_init_complete = true;
> >       mutex_unlock(&pdr->lock);
> >
> > @@ -104,10 +104,10 @@ static void pdr_locator_del_server(struct qmi_handle *qmi,
> >
> >       mutex_lock(&pdr->lock);
> >       pdr->locator_init_complete = false;
> > -     mutex_unlock(&pdr->lock);
> >
> >       pdr->locator_addr.sq_node = 0;
> >       pdr->locator_addr.sq_port = 0;
> > +     mutex_unlock(&pdr->lock);
> >   }
> >
> >   static const struct qmi_ops pdr_locator_ops = {
> > @@ -365,6 +365,7 @@ static int pdr_get_domain_list(struct servreg_get_domain_list_req *req,
> >       if (ret < 0)
> >               return ret;
> >
> > +     mutex_lock(&pdr->lock);
> >       ret = qmi_send_request(&pdr->locator_hdl,
> >                              &pdr->locator_addr,
> >                              &txn, SERVREG_GET_DOMAIN_LIST_REQ,
> > @@ -373,15 +374,16 @@ static int pdr_get_domain_list(struct servreg_get_domain_list_req *req,
> >                              req);
> >       if (ret < 0) {
> >               qmi_txn_cancel(&txn);
> > -             return ret;
> > +             goto err_unlock;
> >       }
> >
> >       ret = qmi_txn_wait(&txn, 5 * HZ);
> >       if (ret < 0) {
> >               pr_err("PDR: %s get domain list txn wait failed: %d\n",
> >                      req->service_name, ret);
> > -             return ret;
> > +             goto err_unlock;
> >       }
> > +     mutex_unlock(&pdr->lock);
>
> I'm not sure it is necessary to hold the the mutex during the
> qmi_txn_wait() since the only variable we are trying to protect is
> locator_addr.
>
> Wouldn't this delay other work like new/del server notifications if this
> qmi service is delayed or non-responsive?
>

I've verified, the addr is stored inside the message data by the
enqueueing functions, so the locator_addr isn't referenced after the
function returns. I'll reduce the locking scope.


-- 
With best wishes
Dmitry