[PATCH] Bluetooth: btmtksdio: fix deadlock in close and reset paths

[ZhaoJinming]

btmtksdio_close() and btmtksdio_reset() call cancel_work_sync() on
bdev->txrx_work while holding the sdio host lock, which is also acquired
by btmtksdio_txrx_work().  If txrx_work is queued when close/reset runs,
a worker thread may start it after the host lock is taken and block in
sdio_claim_host(), while cancel_work_sync() waits for the work to
finish.  The host lock is only released after cancel_work_sync()
returns, so both sides wait forever, deadlocking close/reset.

Fix this by releasing the sdio host lock before calling
cancel_work_sync(), then re-acquiring it afterwards.  The interrupt is
already disabled (sdio_release_irq() in close, C_INT_EN_CLR in reset)
before the work is cancelled, so no new work can be scheduled and
cancel_work_sync() fully quiesces txrx_work before the device is torn
down.  This mirrors the pattern already used by btmtksdio_flush(),
which cancels the work without holding the host lock.

Signed-off-by: ZhaoJinming <zhaojinming at uniontech.com>
---
btmtksdio_close() and btmtksdio_reset() call cancel_work_sync() on
bdev->txrx_work while holding the sdio host lock that
btmtksdio_txrx_work() also acquires. If txrx_work is queued at that
point, a worker thread can start it and block in sdio_claim_host(),
while cancel_work_sync() waits for the work to finish and the host lock
is only released afterwards - a deadlock.

This series releases the host lock around cancel_work_sync() so the work
can always complete, mirroring the pattern already used by
btmtksdio_flush().
---

---
 drivers/bluetooth/btmtksdio.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/bluetooth/btmtksdio.c b/drivers/bluetooth/btmtksdio.c
index c6f80c419e901e71b21e550449250a5a6755d100..879d580226d25ad398105a158de1545dace33718 100644
--- a/drivers/bluetooth/btmtksdio.c
+++ b/drivers/bluetooth/btmtksdio.c
@@ -746,8 +746,16 @@ static int btmtksdio_close(struct hci_dev *hdev)
 
 	sdio_release_irq(bdev->func);
 
+	/* No new work can be scheduled after sdio_release_irq(), so cancel the
+	 * work outside the sdio host lock. btmtksdio_txrx_work() also claims
+	 * the host, so canceling it while holding the lock would deadlock.
+	 */
+	sdio_release_host(bdev->func);
+
 	cancel_work_sync(&bdev->txrx_work);
 
+	sdio_claim_host(bdev->func);
+
 	btmtksdio_fw_pmctrl(bdev);
 
 	clear_bit(BTMTKSDIO_FUNC_ENABLED, &bdev->tx_state);
@@ -1293,8 +1301,18 @@ static void btmtksdio_reset(struct hci_dev *hdev)
 
 	sdio_writel(bdev->func, C_INT_EN_CLR, MTK_REG_CHLPCR, NULL);
 	skb_queue_purge(&bdev->txq);
+
+	/* With the interrupt disabled, the SDIO IRQ handler can no longer
+	 * schedule txrx_work. Cancel the work outside the sdio host lock;
+	 * btmtksdio_txrx_work() also claims the host, so canceling it while
+	 * holding the lock would deadlock.
+	 */
+	sdio_release_host(bdev->func);
+
 	cancel_work_sync(&bdev->txrx_work);
 
+	sdio_claim_host(bdev->func);
+
 	gpiod_set_value_cansleep(bdev->reset, 1);
 	msleep(100);
 	gpiod_set_value_cansleep(bdev->reset, 0);

---
base-commit: 0d839570765118029aa8bf4a95444c6a11aacf85
change-id: 20260806-btmtksdio-deadlock-fix-f9421f1a7879

Best regards,
-- 
ZhaoJinming <zhaojinming at uniontech.com>