netdev - [PATCH v3] Bluetooth: Call shutdown for HCI_USER

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Date:   Tue, 27 Sep 2022 13:17:20 -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 v3] 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 v3:
- Added hci_dev_shutdown to wrap disabling and re-enabling flag.

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 | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 422f7c6911d9..15c75ef4c271 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -4727,6 +4727,31 @@ static void hci_pend_le_actions_clear(struct hci_dev *hdev)
 	BT_DBG("All LE pending actions cleared");
 }

+static int hci_dev_shutdown(struct hci_dev *hdev)
+{
+	int err = 0;
+	/* 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).
+	 */
+	bool was_userchannel =
+		hci_dev_test_and_clear_flag(hdev, HCI_USER_CHANNEL);
+
+	if (!hci_dev_test_flag(hdev, HCI_UNREGISTER) &&
+	    test_bit(HCI_UP, &hdev->flags)) {
+		/* Execute vendor specific shutdown routine */
+		if (hdev->shutdown)
+			err = hdev->shutdown(hdev);
+	}
+
+	if (was_userchannel)
+		hci_dev_set_flag(hdev, HCI_USER_CHANNEL);
+
+	return err;
+}
+
 int hci_dev_close_sync(struct hci_dev *hdev)
 {
 	bool auto_off;
@@ -4746,13 +4771,7 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 		hdev->adv_instance_timeout = 0;
 	}

-	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)
-			err = hdev->shutdown(hdev);
-	}
+	err = hci_dev_shutdown(hdev);

 	if (!test_and_clear_bit(HCI_UP, &hdev->flags)) {
 		cancel_delayed_work_sync(&hdev->cmd_timer);
-- 
2.38.0.rc1.362.ged0d419d3c-goog