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SubjectRe: [PATCH v3 1/3] soc: qcom: Introduce Protection Domain Restart helpers
Hey Bjorn,

Thanks for taking time to review
the series.

On 2020-01-03 02:15, Bjorn Andersson wrote:
> On Sun 29 Dec 21:00 PST 2019, Sibi Sankar wrote:
> [..]
>> diff --git a/drivers/soc/qcom/pdr_interface.c
>> b/drivers/soc/qcom/pdr_interface.c
> [..]
>> +static int servreg_locator_new_server(struct qmi_handle *qmi,
>> + struct qmi_service *svc)
>> +{
>> + struct pdr_handle *pdr = container_of(qmi, struct pdr_handle,
>> + servloc_client);
>> + struct pdr_service *pds, *tmp;
>> +
>> + /* Create a Local client port for QMI communication */
>> + pdr->servloc_addr.sq_family = AF_QIPCRTR;
>> + pdr->servloc_addr.sq_node = svc->node;
>> + pdr->servloc_addr.sq_port = svc->port;
>> +
>> + mutex_lock(&pdr->locator_lock);
>> + pdr->locator_available = true;
>> + mutex_unlock(&pdr->locator_lock);
>> +
>> + /* Service pending lookup requests */
>> + mutex_lock(&pdr->list_lock);
>> + list_for_each_entry_safe(pds, tmp, &pdr->lookups, node) {
>
> No need to make this _safe, as you're not modifying the list in the
> loop.

sure I'll do that

>
>> + if (pds->need_servreg_lookup)
>> + schedule_work(&pdr->servloc_work);
>> + }
>> + mutex_unlock(&pdr->list_lock);
>> +
>> + return 0;
>> +}
> [..]
>> +static void pdr_servreg_link_create(struct pdr_handle *pdr,
>> + struct pdr_service *pds)
>> +{
>> + struct pdr_service *pds_iter, *tmp;
>> + bool link_exists = false;
>> +
>> + /* Check if a QMI link to SERVREG instance already exists */
>> + mutex_lock(&pdr->list_lock);
>> + list_for_each_entry_safe(pds_iter, tmp, &pdr->lookups, node) {
>> + if (pds_iter->instance == pds->instance &&
>
> Flip this condition around and continue if it's not a match, to save
> indentation and to split the two expressions into two distinct checks.

sure I'll do that

>
>> + strcmp(pds_iter->service_path, pds->service_path)) {
>
> Isn't this just saying:
> if (pds_iter == pds)
> continue;
>
> With the purpose of link_exists to be !empty(set(lookups) - pds) ?

More like:
!empty(set(lookups_with_same_instance) - pds)

servreg_link_create was added to re-use
an existing qmi_lookup i.e deal with
PDs running on the same remote processor.
This can be identified by looking for
a lookup with the same instance value
but with a different service path. We
still need to register the service_path
with the servreg service once its up.

>
> But if I read pdr_add_lookup() correctly it's possible that a client
> could call pdr_add_lookup() more than once before pdr_servloc_work() is
> scheduled, in which case "set(lookup) - pds" isn't empty and as such
> you
> won't add the lookup?

holding the lock over entire servloc_work
should handle that scenario? That way we
can ensure qmi_lookup is called atleast
once.

>
>> + link_exists = true;
>> + pds->service_connected = pds_iter->service_connected;
>> + if (pds_iter->service_connected)
>> + pds->need_servreg_register = true;
>> + else
>> + pds->need_servreg_remove = true;
>> + queue_work(pdr->servreg_wq, &pdr->servreg_work);
>> + break;
>> + }
>> + }
> [..]
>> +static void pdr_servloc_work(struct work_struct *work)
>> +{
>> + struct pdr_handle *pdr = container_of(work, struct pdr_handle,
>> + servloc_work);
>> + struct pdr_service *pds, *tmp;
>> + int ret;
>> +
>> + /* Bail out early if PD Mapper is not up */
>> + mutex_lock(&pdr->locator_lock);
>> + if (!pdr->locator_available) {
>> + mutex_unlock(&pdr->locator_lock);
>> + pr_warn("PDR: SERVICE LOCATOR service not available\n");
>> + return;
>> + }
>> + mutex_unlock(&pdr->locator_lock);
>> +
>> + mutex_lock(&pdr->list_lock);
>> + list_for_each_entry_safe(pds, tmp, &pdr->lookups, node) {
>
> As written right now you don't need _safe here, because in the only
> case
> you're modifying the list you end up exiting the loop.

sure

>
>> + if (!pds->need_servreg_lookup)
>> + continue;
>> +
>> + pds->need_servreg_lookup = false;
>> + mutex_unlock(&pdr->list_lock);
>
> You should probably just hold on to list_lock over this entire loop.
>
>> +
>> + ret = pdr_locate_service(pdr, pds);
>> + if (ret < 0) {
>> + if (ret == -ENXIO)
>> + pds->state = SERVREG_LOCATOR_UNKNOWN_SERVICE;
>> + else if (ret == -EAGAIN)
>> + pds->state = SERVREG_LOCATOR_DB_UPDATED;
>
> Isn't this something that we should recover from?

yes its a case where the json
referenced by pd-mapper has been
updated mid lookup. Calling lookup
again should ideally fix this but
we'll have to decide on the max
number of retries. I guess I can
simulate such a scenario with
a custom json file and pd-mapper
changes.

>
>> + else
>> + pds->state = SERVREG_LOCATOR_ERR;
>> +
>> + pr_err("PDR: service lookup for %s failed: %d\n",
>> + pds->service_name, ret);
>> +
>> + /* Remove from lookup list */
>> + mutex_lock(&pdr->list_lock);
>> + list_del(&pds->node);
>
> What should I do in my driver when this happens?

db_updated -> retry should fix
this error

unknown_service -> lookup not found.

^^ With the way pd-mapper is implemented
its not really recoverable until pd-mapper
is restarted with different args.

locator_err -> not really recoverable

>
>> + mutex_unlock(&pdr->list_lock);
>> +
>> + /* Notify Lookup failed */
>> + mutex_lock(&pdr->status_lock);
>> + pdr->status(pdr, pds);
>> + mutex_unlock(&pdr->status_lock);
>> + kfree(pds);
>> + } else {
>> + pdr_servreg_link_create(pdr, pds);
>> + }
>> +
>> + return;
>
> There might be more pds entries with need_servreg_lookup in the list,
> shouldn't we allow this to continue?

but we've already scheduled a
number of workers to deal with
this.

>
> This would though imply that you should hold onto the list_lock over
> the
> entire loop, which I think looks fine.

sure

>
>> + }
>> + mutex_unlock(&pdr->list_lock);
>> +}
>> +
>> +/**
>> + * pdr_add_lookup() - register a tracking request for a PD
>> + * @pdr: PDR client handle
>> + * @service_name: service name of the tracking request
>> + * @service_path: service path of the tracking request
>> + *
>> + * Registering a pdr lookup allows for tracking the life cycle of the
>> PD.
>> + *
>> + * Return: 0 on success, negative errno on failure.
>> + */
>> +int pdr_add_lookup(struct pdr_handle *pdr, const char *service_name,
>> + const char *service_path)
>> +{
>> + struct pdr_service *pds, *pds_iter, *tmp;
>> + int ret;
>> +
>> + if (!service_name || strlen(service_name) > SERVREG_NAME_LENGTH ||
>> + !service_path || strlen(service_path) > SERVREG_NAME_LENGTH)
>> + return -EINVAL;
>> +
>> + pds = kzalloc(sizeof(*pds), GFP_KERNEL);
>> + if (!pds)
>> + return -ENOMEM;
>> +
>> + pds->service = SERVREG_NOTIFIER_SERVICE;
>> + strcpy(pds->service_name, service_name);
>> + strcpy(pds->service_path, service_path);
>> + pds->need_servreg_lookup = true;
>> +
>> + mutex_lock(&pdr->list_lock);
>> + list_for_each_entry_safe(pds_iter, tmp, &pdr->lookups, node) {
>
> No _safe

Thanks will update

>
>> + if (!strcmp(pds_iter->service_path, service_path)) {
>> + mutex_unlock(&pdr->list_lock);
>> + ret = -EALREADY;
>> + goto err;
>> + }
>> + }
>> +
>> + list_add(&pds->node, &pdr->lookups);
>> + mutex_unlock(&pdr->list_lock);
>> +
>> + schedule_work(&pdr->servloc_work);
>> +
>> + return 0;
>> +err:
>> + kfree(pds);
>> +
>> + return ret;
>> +}
>> +EXPORT_SYMBOL(pdr_add_lookup);
>> +
>> +/**
>> + * pdr_restart_pd() - restart PD
>> + * @pdr: PDR client handle
>> + * @service_path: service path of restart request
>> + *
>> + * Restarts the PD tracked by the PDR client handle for a given
>> service path.
>> + *
>> + * Return: 0 on success, negative errno on failure.
>> + */
>> +int pdr_restart_pd(struct pdr_handle *pdr, const char *service_path)
>> +{
>> + struct servreg_restart_pd_req req;
>> + struct servreg_restart_pd_resp resp;
>> + struct pdr_service *pds = NULL, *pds_iter, *tmp;
>> + struct qmi_txn txn;
>> + int ret;
>> +
>> + if (!service_path || strlen(service_path) > SERVREG_NAME_LENGTH)
>> + return -EINVAL;
>> +
>> + mutex_lock(&pdr->list_lock);
>> + list_for_each_entry_safe(pds_iter, tmp, &pdr->lookups, node) {
>> + if (!pds_iter->service_connected)
>> + continue;
>> +
>> + if (!strcmp(pds_iter->service_path, service_path)) {
>> + pds = pds_iter;
>> + break;
>> + }
>> + }
>> + mutex_unlock(&pdr->list_lock);
>> +
>> + if (!pds)
>
> Given that you may only call pdr_restart_pd() on something created by
> first calling pdr_add_lookup(), how about returning the struct
> pdr_service from pdr_add_lookup() instead and then have the client pass
> that as an argument to this function.
>
> Most clients doesn't care about pdr_restart_pd() so they would only
> have
> to IS_ERR(pdr_add_lookup()) anyways, and the ones that care can carry
> the returned pointer.
>
>
> Note that the struct pdr_service doesn't have to be defined in a way
> that it's possible to dereference by clients.

sure will update the design in the
next re-spin.

>
>> + return -EINVAL;
>> +
>> + /* Prepare req message */
>> + strcpy(req.service_path, pds->service_path);
>> +
>> + ret = qmi_txn_init(&pdr->servreg_client, &txn,
>> + servreg_restart_pd_resp_ei,
>> + &resp);
>> + if (ret < 0)
>> + return ret;
>> +
>> + ret = qmi_send_request(&pdr->servreg_client, &pdr->servreg_addr,
>> + &txn, SERVREG_RESTART_PD_REQ,
>> + SERVREG_RESTART_PD_REQ_MAX_LEN,
>> + servreg_restart_pd_req_ei, &req);
>> + if (ret < 0) {
>> + qmi_txn_cancel(&txn);
>> + return ret;
>> + }
>> +
>> + ret = qmi_txn_wait(&txn, 5 * HZ);
>> + if (ret < 0) {
>> + pr_err("PDR: %s PD restart txn wait failed: %d\n",
>> + pds->service_path, ret);
>> + return ret;
>> + }
>> +
>> + /* Check response if PDR is disabled */
>> + if (resp.resp.result == QMI_RESULT_FAILURE_V01 &&
>> + resp.resp.error == QMI_ERR_DISABLED_V01) {
>> + pr_err("PDR: %s PD restart is disabled: 0x%x\n",
>> + pds->service_path, resp.resp.error);
>> + return -EOPNOTSUPP;
>> + }
>> +
>> + /* Check the response for other error case*/
>> + if (resp.resp.result != QMI_RESULT_SUCCESS_V01) {
>> + pr_err("PDR: %s request for PD restart failed: 0x%x\n",
>> + pds->service_path, resp.resp.error);
>> + return -EREMOTEIO;
>> + }
>> +
>> + return ret;
>> +}
>> +EXPORT_SYMBOL(pdr_restart_pd);
> [..]
>> +/**
>> + * struct pdr_service - context to track lookups/restarts
>> + * @service_name: name of the service running on the PD
>> + * @service_path: service path of the PD
>> + * @service_data_valid: indicates if service_data field has valid
>> data
>> + * @service_data: service data provided by servreg_locator service
>> + * @need_servreg_lookup: state flag for tracking servreg lookup
>> requests
>> + * @need_servreg_register: state flag for tracking pending servreg
>> register
>> + * @need_servreg_remove: state flag for tracking pending servreg
>> remove
>> + * @service_connected: current state of servreg_notifier qmi service
>> + * @state: current state of PD
>> + * @service: servreg_notifer service type
>> + * @instance: instance id of the @service
>> + * @priv: handle for client's use
>> + * @node: list_head for house keeping
>> + */
>> +struct pdr_service {
>
> This is primarily internal bookkeeping, how about not exposing it to
> the
> clients? This would imply that status() would have to be called with
> pdr_service->priv and pdr_service->state as arguments instead.

sure will update the design in the
next re-spin.

>
>> + char service_name[SERVREG_NAME_LENGTH + 1];
>> + char service_path[SERVREG_NAME_LENGTH + 1];
>> +
>> + u8 service_data_valid;
>> + u32 service_data;
>> +
>> + bool need_servreg_lookup;
>> + bool need_servreg_register;
>> + bool need_servreg_remove;
>> + bool service_connected;
>> + int state;
>> +
>> + unsigned int instance;
>> + unsigned int service;
>> +
>> + void *priv;
>> + struct list_head node;
>> +};
>> +
> [..]
>> + void (*status)(struct pdr_handle *pdr, struct pdr_service *pds);
>> +};
>
> Regards,
> Bjorn

--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project.

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