linux-kernel - Re: [PATCH v8 1/5] soc: qcom: pdr: protect locator

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Date: Wed, 5 Jun 2024 15:48:08 -0700
From: Chris Lew <quic_clew@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Bjorn Andersson
	<andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Sibi Sankar
	<quic_sibis@...cinc.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
CC: <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>,
        Johan Hovold <johan+linaro@...nel.org>,
        Xilin Wu <wuxilin123@...il.com>,
        Bryan O'Donoghue
	<bryan.odonoghue@...aro.org>,
        Steev Klimaszewski <steev@...i.org>,
        "Alexey
 Minnekhanov" <alexeymin@...tmarketos.org>,
        Neil Armstrong
	<neil.armstrong@...aro.org>
Subject: Re: [PATCH v8 1/5] soc: qcom: pdr: protect locator_addr with the main
 mutex

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?

Thanks,
Chris

>   
>   	if (resp->resp.result != QMI_RESULT_SUCCESS_V01) {
>   		pr_err("PDR: %s get domain list failed: 0x%x\n",
> @@ -390,6 +392,11 @@ static int pdr_get_domain_list(struct servreg_get_domain_list_req *req,
>   	}
>   
>   	return 0;
> +
> +err_unlock:
> +	mutex_unlock(&pdr->lock);
> +
> +	return ret;
>   }
>