netdev - [PATCH v2] Bluetooth: Call shutdown for HCI_USER

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Date:   Mon, 26 Sep 2022 16:44:04 -0700
From:   Abhishek Pandit-Subedi <abhishekpandit@...gle.com>
To:     linux-bluetooth@...r.kernel.org
Cc:     Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH v2] Bluetooth: Call shutdown for HCI_USER_CHANNEL

From: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>

Some drivers depend on shutdown being called for proper operation.
Unset HCI_USER_CHANNEL and call the full close routine since shutdown is
complementary to setup.

Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
---

Using hci_qca, we can get the controller into a bad state simply by
trying to bind to userchannel twice (open+bind+close, then open+bind).
Without running the shutdown routine, the device seems to get into a bad
state. A similar bug also occurs with btmtksdio (using MT7921).

This change properly runs the shutdown routine, which should be
complementary to setup. The reason it unsets the HCI_USER_CHANNEL flag
is that some drivers have complex operations in their shutdown routine
(including sending hci packets) and we need to support the normal data
path for them (including cmd_timeout + recovery mechanisms).

Note for v2: I've gotten a chance to test this on more devices
and figure out why it wasn't working before in v1. I found two problems:
I had a signal pending (SIGTERM) that was messing things up in the
socket release function and the HCI_USER_CHANNEL flag was preventing
hci_sync from operating properly during shutdown on Intel chipsets
(which use the sync functions to send a reset command + other commands
sometimes).

This was tested with hci_qca (QCA6174-A-3), btmtksdio (MT7921-SDIO)
and btusb (with AX200).


Changes in v2:
- Clear HCI_USER_CHANNEL flag at start of close and restore at end.
- Add comment explaning why we need to clear flag and run shutdown.

 net/bluetooth/hci_sync.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 422f7c6911d9..f9591fcefb8d 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -4731,9 +4731,18 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 {
 	bool auto_off;
 	int err = 0;
+	bool was_userchannel;
 
 	bt_dev_dbg(hdev, "");
 
+	/* Similar to how we first do setup and then set the exclusive access
+	 * bit for userspace, we must first unset userchannel and then clean up.
+	 * Otherwise, the kernel can't properly use the hci channel to clean up
+	 * the controller (some shutdown routines require sending additional
+	 * commands to the controller for example).
+	 */
+	was_userchannel = hci_dev_test_and_clear_flag(hdev, HCI_USER_CHANNEL);
+
 	cancel_delayed_work(&hdev->power_off);
 	cancel_delayed_work(&hdev->ncmd_timer);
 	cancel_delayed_work(&hdev->le_scan_disable);
@@ -4747,7 +4756,6 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 	}
 
 	if (!hci_dev_test_flag(hdev, HCI_UNREGISTER) &&
-	    !hci_dev_test_flag(hdev, HCI_USER_CHANNEL) &&
 	    test_bit(HCI_UP, &hdev->flags)) {
 		/* Execute vendor specific shutdown routine */
 		if (hdev->shutdown)
@@ -4756,6 +4764,8 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 
 	if (!test_and_clear_bit(HCI_UP, &hdev->flags)) {
 		cancel_delayed_work_sync(&hdev->cmd_timer);
+		if (was_userchannel)
+			hci_dev_set_flag(hdev, HCI_USER_CHANNEL);
 		return err;
 	}
 
@@ -4795,7 +4805,7 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 	auto_off = hci_dev_test_and_clear_flag(hdev, HCI_AUTO_OFF);
 
 	if (!auto_off && hdev->dev_type == HCI_PRIMARY &&
-	    !hci_dev_test_flag(hdev, HCI_USER_CHANNEL) &&
+	    !was_userchannel &&
 	    hci_dev_test_flag(hdev, HCI_MGMT))
 		__mgmt_power_off(hdev);
 
@@ -4808,7 +4818,7 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 
 	hci_sock_dev_event(hdev, HCI_DEV_DOWN);
 
-	if (!hci_dev_test_flag(hdev, HCI_USER_CHANNEL)) {
+	if (!was_userchannel)
 		aosp_do_close(hdev);
 		msft_do_close(hdev);
 	}
@@ -4858,6 +4868,9 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 	memset(hdev->dev_class, 0, sizeof(hdev->dev_class));
 	bacpy(&hdev->random_addr, BDADDR_ANY);
 
+	if (was_userchannel)
+		hci_dev_set_flag(hdev, HCI_USER_CHANNEL);
+
 	hci_dev_put(hdev);
 	return err;
 }
-- 
2.37.3.998.g577e59143f-goog