Re: [PATCH] Bluetooth: btusb: Prevent autosuspend when le_scan_disable work is pending
From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date: 2025-10-31 14:35:37
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Subsystem:
bluetooth subsystem, the rest · Maintainers:
Marcel Holtmann, Luiz Augusto von Dentz, Linus Torvalds
Hi, On Fri, Oct 31, 2025 at 4:15 AM Linmao Li [off-list ref] wrote:
When USB autosuspend occurs while le_scan_disable work is scheduled,
HCI commands sent by the work fail with timeout, leaving LE scan in
an inconsistent state.
Scenario:
T=0: LE scan starts, le_scan_disable work queued (+10240ms)
T=8s: Autosuspend check: tx_in_flight=0, suspend proceeds
T=10s: le_scan_disable work executes on suspended device
→ HCI command 0x2042 times out
The tx_in_flight check only protects actively transmitted URBs, missing
the window where work is queued but hasn't submitted its URB yet.
Fix by checking delayed_work_pending(&hdev->le_scan_disable) during
autosuspend. Return -EBUSY if pending to block suspend until work
completes. Only set BTUSB_SUSPENDING after all checks pass to avoid
leaving the flag set if suspend is aborted.Hmm, we could also just cancel the work then, in face we do have hci_suspend_sync->hci_stop_discovery_sync->cancel_delayed_work(&hdev->le_scan_disable); but perhaps it is not being called always because HCI_LE_SCAN is not enabled, so I wonder if we should do something like:
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 1cbdd2ce03f2..59618fde7bcb 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c@@ -5464,6 +5464,11 @@ int hci_stop_discovery_sync(struct hci_dev *hdev) bt_dev_dbg(hdev, "state %u", hdev->discovery.state); + /* Always stop le_scan_disable since that works as discovery timer for + * the rounds of discovery irrespective of the discovery type. + */ + cancel_delayed_work(&hdev->le_scan_disable); + if (d->state == DISCOVERY_FINDING || d->state == DISCOVERY_STOPPING) { if (test_bit(HCI_INQUIRY, &hdev->flags)) { err = __hci_cmd_sync_status(hdev, HCI_OP_INQUIRY_CANCEL,
@@ -5472,14 +5477,9 @@ int hci_stop_discovery_sync(struct hci_dev *hdev) return err; } - if (hci_dev_test_flag(hdev, HCI_LE_SCAN)) { - cancel_delayed_work(&hdev->le_scan_disable); - - err = hci_scan_disable_sync(hdev); - if (err) - return err; - } - + err = hci_scan_disable_sync(hdev); + if (err) + return err; } else { err = hci_scan_disable_sync(hdev); if (err)
We may as well rename/reworkd le_scan_disable to discovery.work since that acts as I commented above it works as discovery timer not just le_scan_disable.
quoted hunk ↗ jump to hunk
Signed-off-by: Linmao Li <redacted> --- drivers/bluetooth/btusb.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c index 5e9ebf0c5312..a344ea1dc466 100644 --- a/drivers/bluetooth/btusb.c +++ b/drivers/bluetooth/btusb.c@@ -4389,6 +4389,7 @@ static void btusb_disconnect(struct usb_interface *intf) static int btusb_suspend(struct usb_interface *intf, pm_message_t message) { struct btusb_data *data = usb_get_intfdata(intf); + struct hci_dev *hdev = data->hdev; BT_DBG("intf %p", intf);@@ -4402,14 +4403,19 @@ static int btusb_suspend(struct usb_interface *intf, pm_message_t message) return 0; spin_lock_irq(&data->txlock); - if (!(PMSG_IS_AUTO(message) && data->tx_in_flight)) { - set_bit(BTUSB_SUSPENDING, &data->flags); - spin_unlock_irq(&data->txlock); - } else { + if (PMSG_IS_AUTO(message) && data->tx_in_flight) { spin_unlock_irq(&data->txlock); data->suspend_count--; return -EBUSY; } + spin_unlock_irq(&data->txlock); + + if (PMSG_IS_AUTO(message) && delayed_work_pending(&hdev->le_scan_disable)) { + data->suspend_count--; + return -EBUSY; + }
+
+ set_bit(BTUSB_SUSPENDING, &data->flags);
cancel_work_sync(&data->work);
--
2.25.1-- Luiz Augusto von Dentz