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 <20240512-qcom-pd-mapper-v8-1-5ecbb276fcc0@linaro.org> <d9a2004a-0a3b-41a6-92a4-eea7b1b3f804@quicinc.com>
In-Reply-To: <d9a2004a-0a3b-41a6-92a4-eea7b1b3f804@quicinc.com>
From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date: Thu, 6 Jun 2024 12:15:41 +0300
Message-ID: <CAA8EJpq=vuvWMcPf65nezDXFmWjhwMziuMzVtSDiM81_HD5UMA@mail.gmail.com>
Subject: Re: [PATCH v8 1/5] soc: qcom: pdr: protect locator_addr with the main mutex
To: Chris Lew <quic_clew@quicinc.com>
Cc: Bjorn Andersson <andersson@kernel.org>, Konrad Dybcio <konrad.dybcio@linaro.org>, 
	Sibi Sankar <quic_sibis@quicinc.com>, Mathieu Poirier <mathieu.poirier@linaro.org>, 
	linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, 
	linux-remoteproc@vger.kernel.org, Johan Hovold <johan+linaro@kernel.org>, 
	Xilin Wu <wuxilin123@gmail.com>, "Bryan O'Donoghue" <bryan.odonoghue@linaro.org>, 
	Steev Klimaszewski <steev@kali.org>, Alexey Minnekhanov <alexeymin@postmarketos.org>, 
	Neil Armstrong <neil.armstrong@linaro.org>
Content-Type: text/plain; charset="UTF-8"

On Thu, 6 Jun 2024 at 01:48, Chris Lew <quic_clew@quicinc.com> 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