[PATCH 1/4] wifi: ath12k: Decrease ath12k_mac_op_remain_on_channel() stack usage

Kalle Valo
2024-12-17T20:26:24Z

Building the ath12k driver with llvm-18.1.7-x86_64 produces the warning:

drivers/net/wireless/ath/ath12k/mac.c:10028:12: warning: stack frame size (1080) exceeds limit (1024) in 'ath12k_mac_op_remain_on_channel' [-Wframe-larger-than]

A major contributor to the stack usage in this function is:

struct ath12k_wmi_scan_req_arg arg;

Avoid the excess stack usage by dynamically allocating arg instead of
declaring it on the stack. As part of the effort use __free() for both
this new allocation as well as the existing chan_list allocation, and
since then no central cleanup is required, replace all cleanup gotos
with returns.

Tested-on: QCN9274 hw2.0 PCI WLAN.WBE.1.3.1-00173-QCAHKSWPL_SILICONZ-1
Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
---
drivers/net/wireless/ath/ath12k/mac.c | 76 ++++++++++++---------------
1 file changed, 33 insertions(+), 43 deletions(-)

diff --git a/drivers/net/wireless/ath/ath12k/mac.c b/drivers/net/wireless/ath/ath12k/mac.c
index 186765fa95f5..05d2c75e5df2 100644
--- a/drivers/net/wireless/ath/ath12k/mac.c
+++ b/drivers/net/wireless/ath/ath12k/mac.c
@@ -10054,7 +10054,6 @@ static int ath12k_mac_op_remain_on_channel(struct ieee80211_hw *hw,
{
struct ath12k_vif *ahvif = ath12k_vif_to_ahvif(vif);
struct ath12k_hw *ah = ath12k_hw_to_ah(hw);
- struct ath12k_wmi_scan_req_arg arg;
struct ath12k_link_vif *arvif;
struct ath12k *ar;
u32 scan_time_msec;
@@ -10065,10 +10064,8 @@ static int ath12k_mac_op_remain_on_channel(struct ieee80211_hw *hw,
lockdep_assert_wiphy(hw->wiphy);

ar = ath12k_mac_select_scan_device(hw, vif, chan->center_freq);
- if (!ar) {
- ret = -EINVAL;
- goto exit;
- }
+ if (!ar)
+ return -EINVAL;

/* check if any of the links of ML VIF is already started on
* radio(ar) correpsondig to given scan frequency and use it,
@@ -10087,15 +10084,11 @@ static int ath12k_mac_op_remain_on_channel(struct ieee80211_hw *hw,
* always on the same band for the vif
*/
if (arvif->is_created) {
- if (WARN_ON(!arvif->ar)) {
- ret = -EINVAL;
- goto exit;
- }
+ if (WARN_ON(!arvif->ar))
+ return -EINVAL;

- if (ar != arvif->ar && arvif->is_started) {
- ret = -EBUSY;
- goto exit;
- }
+ if (ar != arvif->ar && arvif->is_started)
+ return -EBUSY;

if (ar != arvif->ar) {
ath12k_mac_remove_link_interface(hw, arvif);
@@ -10112,7 +10105,7 @@ static int ath12k_mac_op_remain_on_channel(struct ieee80211_hw *hw,
if (ret) {
ath12k_warn(ar->ab, "unable to create scan vdev for roc: %d\n",
ret);
- goto exit;
+ return ret;
}
}

@@ -10140,37 +10133,41 @@ static int ath12k_mac_op_remain_on_channel(struct ieee80211_hw *hw,
spin_unlock_bh(&ar->data_lock);

if (ret)
- goto exit;
+ return ret;

scan_time_msec = hw->wiphy->max_remain_on_channel_duration * 2;

- memset(&arg, 0, sizeof(arg));
- ath12k_wmi_start_scan_init(ar, &arg);
- arg.num_chan = 1;
- arg.chan_list = kcalloc(arg.num_chan, sizeof(*arg.chan_list),
- GFP_KERNEL);
- if (!arg.chan_list) {
- ret = -ENOMEM;
- goto exit;
- }
+ struct ath12k_wmi_scan_req_arg *arg __free(kfree) =
+ kzalloc(sizeof(*arg), GFP_KERNEL);
+ if (!arg)
+ return -ENOMEM;

- arg.vdev_id = arvif->vdev_id;
- arg.scan_id = ATH12K_SCAN_ID;
- arg.chan_list[0] = chan->center_freq;
- arg.dwell_time_active = scan_time_msec;
- arg.dwell_time_passive = scan_time_msec;
- arg.max_scan_time = scan_time_msec;
- arg.scan_f_passive = 1;
- arg.burst_duration = duration;
+ ath12k_wmi_start_scan_init(ar, arg);
+ arg->num_chan = 1;

- ret = ath12k_start_scan(ar, &arg);
+ u32 *chan_list __free(kfree) = kcalloc(arg->num_chan, sizeof(*chan_list),
+ GFP_KERNEL);
+ if (!chan_list)
+ return -ENOMEM;
+
+ arg->chan_list = chan_list;
+ arg->vdev_id = arvif->vdev_id;
+ arg->scan_id = ATH12K_SCAN_ID;
+ arg->chan_list[0] = chan->center_freq;
+ arg->dwell_time_active = scan_time_msec;
+ arg->dwell_time_passive = scan_time_msec;
+ arg->max_scan_time = scan_time_msec;
+ arg->scan_f_passive = 1;
+ arg->burst_duration = duration;
+
+ ret = ath12k_start_scan(ar, arg);
if (ret) {
ath12k_warn(ar->ab, "failed to start roc scan: %d\n", ret);

spin_lock_bh(&ar->data_lock);
ar->scan.state = ATH12K_SCAN_IDLE;
spin_unlock_bh(&ar->data_lock);
- goto free_chan_list;
+ return ret;
}

ret = wait_for_completion_timeout(&ar->scan.on_channel, 3 * HZ);
@@ -10179,20 +10176,13 @@ static int ath12k_mac_op_remain_on_channel(struct ieee80211_hw *hw,
ret = ath12k_scan_stop(ar);
if (ret)
ath12k_warn(ar->ab, "failed to stop scan: %d\n", ret);
- ret = -ETIMEDOUT;
- goto free_chan_list;
+ return -ETIMEDOUT;
}

ieee80211_queue_delayed_work(hw, &ar->scan.timeout,
msecs_to_jiffies(duration));

- ret = 0;
-
-free_chan_list:
- kfree(arg.chan_list);
-
-exit:
- return ret;
+ return 0;
}

static void ath12k_mac_op_set_rekey_data(struct ieee80211_hw *hw,
--
2.39.5