Re: [PATCH v3 1/4] remoteproc: sysmon: Ensure remote notification ordering

On 2020-11-21 21:41, Bjorn Andersson wrote:

The reliance on the remoteproc's state for determining when to send sysmon notifications to a remote processor is racy with regard to concurrent remoteproc operations.

Further more the advertisement of the state of other remote processor to a newly started remote processor might not only send the wrong state, but might result in a stream of state changes that are out of order.

Address this by introducing state tracking within the sysmon instances themselves and extend the locking to ensure that the notifications are consistent with this state.

Fixes: 1f36ab3f6e3b ("remoteproc: sysmon: Inform current rproc about all active rprocs") Fixes: 1877f54f75ad ("remoteproc: sysmon: Add notifications for events") Fixes: 1fb82ee806d1 ("remoteproc: qcom: Introduce sysmon") Cc: stable@vger.kernel.org Signed-off-by: Bjorn Andersson bjorn.andersson@linaro.org

---

Changes since v2:

• Hold sysmon_lock during traversal of sysmons in sysmon_start()

drivers/remoteproc/qcom_sysmon.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/remoteproc/qcom_sysmon.c b/drivers/remoteproc/qcom_sysmon.c index 9eb2f6bccea6..b37b111b15b3 100644 --- a/drivers/remoteproc/qcom_sysmon.c +++ b/drivers/remoteproc/qcom_sysmon.c @@ -22,6 +22,9 @@ struct qcom_sysmon { struct rproc_subdev subdev; struct rproc *rproc;

• int state;

• struct mutex state_lock;

• struct list_head node;

  const char *name;

@@ -448,7 +451,10 @@ static int sysmon_prepare(struct rproc_subdev *subdev) .ssr_event = SSCTL_SSR_EVENT_BEFORE_POWERUP };

• mutex_lock(&sysmon->state_lock);

• sysmon->state = SSCTL_SSR_EVENT_BEFORE_POWERUP; blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)&event);

• mutex_unlock(&sysmon->state_lock);

  return 0;

} @@ -472,20 +478,25 @@ static int sysmon_start(struct rproc_subdev *subdev) .ssr_event = SSCTL_SSR_EVENT_AFTER_POWERUP };

• mutex_lock(&sysmon->state_lock);

• sysmon->state = SSCTL_SSR_EVENT_AFTER_POWERUP; blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)&event);

• mutex_unlock(&sysmon->state_lock);

  mutex_lock(&sysmon_lock); list_for_each_entry(target, &sysmon_list, node) {

• if (target == sysmon ||
  

•     target->rproc->state != RPROC_RUNNING)
  

• if (target == sysmon)
  continue;
  
  

• mutex_lock(&target->state_lock);
  

  event.subsys_name = target->name;

• event.ssr_event = target->state;
  
  

  if (sysmon->ssctl_version == 2) ssctl_send_event(sysmon, &event); else if (sysmon->ept) sysmon_send_event(sysmon, &event);

• mutex_unlock(&target->state_lock);
  

  } mutex_unlock(&sysmon_lock);

@@ -500,7 +511,10 @@ static void sysmon_stop(struct rproc_subdev *subdev, bool crashed) .ssr_event = SSCTL_SSR_EVENT_BEFORE_SHUTDOWN };

• mutex_lock(&sysmon->state_lock);

• sysmon->state = SSCTL_SSR_EVENT_BEFORE_SHUTDOWN; blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)&event);

• mutex_unlock(&sysmon->state_lock);

  /* Don't request graceful shutdown if we've crashed */ if (crashed)

@@ -521,7 +535,10 @@ static void sysmon_unprepare(struct rproc_subdev *subdev) .ssr_event = SSCTL_SSR_EVENT_AFTER_SHUTDOWN };

• mutex_lock(&sysmon->state_lock);
• sysmon->state = SSCTL_SSR_EVENT_AFTER_SHUTDOWN; blocking_notifier_call_chain(&sysmon_notifiers, 0, (void *)&event);
• mutex_unlock(&sysmon->state_lock);

}

/** @@ -534,11 +551,10 @@ static int sysmon_notify(struct notifier_block *nb, unsigned long event, void *data) { struct qcom_sysmon *sysmon = container_of(nb, struct qcom_sysmon, nb);

• struct rproc *rproc = sysmon->rproc; struct sysmon_event *sysmon_event = data;

  /* Skip non-running rprocs and the originating instance */

• if (rproc->state != RPROC_RUNNING ||

• if (sysmon->state != SSCTL_SSR_EVENT_AFTER_POWERUP || !strcmp(sysmon_event->subsys_name, sysmon->name)) { dev_dbg(sysmon->dev, "not notifying %s\n", sysmon->name); return NOTIFY_DONE;

@@ -591,6 +607,7 @@ struct qcom_sysmon *qcom_add_sysmon_subdev(struct rproc *rproc, init_completion(&sysmon->ind_comp); init_completion(&sysmon->shutdown_comp); mutex_init(&sysmon->lock);

• mutex_init(&sysmon->state_lock);

  sysmon->shutdown_irq = of_irq_get_byname(sysmon->dev->of_node, "shutdown-ack");

Reviewed-by: Rishabh Bhatnagar rishabhb@codeaurora.org