[PATCH v2 05/33] staging: wfx: avoid possible lock-up during scan

Jerome Pouiller
2021-09-13T08:32:21Z

If the environment is noisy, the device may take time to send scan
requests. Thus, scan requests durations > 5s have already been observed.
During the scan, traffic is neither received, neither sent. From the
user point-of-view, the traffic is frozen for a long time.

This patch reworks the scan processing. It gives to the device a smaller
time budget than previously. However, it does not expect the scan to be
complete and it is able to send another scan request to finish the work.

A big part of the patch aims to avoid an infinite loop if the device
goes crazy.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
---
drivers/staging/wfx/hif_rx.c | 3 ++-
drivers/staging/wfx/scan.c | 48 ++++++++++++++++++++++--------------
drivers/staging/wfx/scan.h | 2 +-
drivers/staging/wfx/wfx.h | 1 +
4 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/drivers/staging/wfx/hif_rx.c b/drivers/staging/wfx/hif_rx.c
index 9fca7f26372a..a60c4a4ba935 100644
--- a/drivers/staging/wfx/hif_rx.c
+++ b/drivers/staging/wfx/hif_rx.c
@@ -175,13 +175,14 @@ static int hif_scan_complete_indication(struct wfx_dev *wdev,
const void *buf)
{
struct wfx_vif *wvif = wdev_to_wvif(wdev, hif->interface);
+ const struct hif_ind_scan_cmpl *body = buf;

if (!wvif) {
dev_warn(wdev->dev, "%s: received event for non-existent vif\n", __func__);
return -EIO;
}

- wfx_scan_complete(wvif);
+ wfx_scan_complete(wvif, body->num_channels_completed);

return 0;
}
diff --git a/drivers/staging/wfx/scan.c b/drivers/staging/wfx/scan.c
index 1e03b130049b..695b06974194 100644
--- a/drivers/staging/wfx/scan.c
+++ b/drivers/staging/wfx/scan.c
@@ -41,7 +41,7 @@ static int update_probe_tmpl(struct wfx_vif *wvif,
static int send_scan_req(struct wfx_vif *wvif,
struct cfg80211_scan_request *req, int start_idx)
{
- int i, ret, timeout;
+ int i, ret;
struct ieee80211_channel *ch_start, *ch_cur;

for (i = start_idx; i < req->n_channels; i++) {
@@ -56,31 +56,31 @@ static int send_scan_req(struct wfx_vif *wvif,
wfx_tx_lock_flush(wvif->wdev);
wvif->scan_abort = false;
reinit_completion(&wvif->scan_complete);
- ret = hif_scan(wvif, req, start_idx, i - start_idx, &timeout);
+ ret = hif_scan(wvif, req, start_idx, i - start_idx, NULL);
if (ret) {
- ret = -EIO;
- goto err_scan_start;
+ wfx_tx_unlock(wvif->wdev);
+ return -EIO;
}
- ret = wait_for_completion_timeout(&wvif->scan_complete, timeout);
+ ret = wait_for_completion_timeout(&wvif->scan_complete, 1 * HZ);
if (!ret) {
- dev_notice(wvif->wdev->dev, "scan timeout\n");
hif_stop_scan(wvif);
ret = wait_for_completion_timeout(&wvif->scan_complete, 1 * HZ);
- if (!ret)
- dev_err(wvif->wdev->dev, "scan didn't stop\n");
+ dev_dbg(wvif->wdev->dev, "scan timeout (%d channels done)\n",
+ wvif->scan_nb_chan_done);
+ }
+ if (!ret) {
+ dev_err(wvif->wdev->dev, "scan didn't stop\n");
ret = -ETIMEDOUT;
- goto err_timeout;
- }
- if (wvif->scan_abort) {
+ } else if (wvif->scan_abort) {
dev_notice(wvif->wdev->dev, "scan abort\n");
ret = -ECONNABORTED;
- goto err_timeout;
+ } else if (wvif->scan_nb_chan_done > i - start_idx) {
+ ret = -EIO;
+ } else {
+ ret = wvif->scan_nb_chan_done;
}
- ret = i - start_idx;
-err_timeout:
if (req->channels[start_idx]->max_power != wvif->vif->bss_conf.txpower)
hif_set_output_power(wvif, wvif->vif->bss_conf.txpower);
-err_scan_start:
wfx_tx_unlock(wvif->wdev);
return ret;
}
@@ -94,7 +94,7 @@ void wfx_hw_scan_work(struct work_struct *work)
{
struct wfx_vif *wvif = container_of(work, struct wfx_vif, scan_work);
struct ieee80211_scan_request *hw_req = wvif->scan_req;
- int chan_cur, ret;
+ int chan_cur, ret, err;

mutex_lock(&wvif->wdev->conf_mutex);
mutex_lock(&wvif->scan_lock);
@@ -105,11 +105,20 @@ void wfx_hw_scan_work(struct work_struct *work)
}
update_probe_tmpl(wvif, &hw_req->req);
chan_cur = 0;
+ err = 0;
do {
ret = send_scan_req(wvif, &hw_req->req, chan_cur);
- if (ret > 0)
+ if (ret > 0) {
chan_cur += ret;
- } while (ret > 0 && chan_cur < hw_req->req.n_channels);
+ err = 0;
+ }
+ if (!ret)
+ err++;
+ if (err > 2) {
+ dev_err(wvif->wdev->dev, "scan has not been able to start\n");
+ ret = -ETIMEDOUT;
+ }
+ } while (ret >= 0 && chan_cur < hw_req->req.n_channels);
mutex_unlock(&wvif->scan_lock);
mutex_unlock(&wvif->wdev->conf_mutex);
__ieee80211_scan_completed_compat(wvif->wdev->hw, ret < 0);
@@ -134,7 +143,8 @@ void wfx_cancel_hw_scan(struct ieee80211_hw *hw, struct ieee80211_vif *vif)
hif_stop_scan(wvif);
}

-void wfx_scan_complete(struct wfx_vif *wvif)
+void wfx_scan_complete(struct wfx_vif *wvif, int nb_chan_done)
{
+ wvif->scan_nb_chan_done = nb_chan_done;
complete(&wvif->scan_complete);
}
diff --git a/drivers/staging/wfx/scan.h b/drivers/staging/wfx/scan.h
index c7496a766478..562ca1321daf 100644
--- a/drivers/staging/wfx/scan.h
+++ b/drivers/staging/wfx/scan.h
@@ -17,6 +17,6 @@ void wfx_hw_scan_work(struct work_struct *work);
int wfx_hw_scan(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
struct ieee80211_scan_request *req);
void wfx_cancel_hw_scan(struct ieee80211_hw *hw, struct ieee80211_vif *vif);
-void wfx_scan_complete(struct wfx_vif *wvif);
+void wfx_scan_complete(struct wfx_vif *wvif, int nb_chan_done);

#endif /* WFX_SCAN_H */
diff --git a/drivers/staging/wfx/wfx.h b/drivers/staging/wfx/wfx.h
index 94898680ccde..56f1e4bb0b57 100644
--- a/drivers/staging/wfx/wfx.h
+++ b/drivers/staging/wfx/wfx.h
@@ -85,6 +85,7 @@ struct wfx_vif {
struct mutex scan_lock;
struct work_struct scan_work;
struct completion scan_complete;
+ int scan_nb_chan_done;
bool scan_abort;
struct ieee80211_scan_request *scan_req;

--
2.33.0