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

[Luiz Augusto von Dentz]

Hi ZhaoJinming,

On Thu, Aug 6, 2026 at 2:36 AM ZhaoJinming <zhaojinming at uniontech.com> wrote:
>
> 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>

Sashiko found a problem:

https://sashiko.dev/#/patchset/FD5D03449312D17C%2B20260806-btmtksdio-deadlock-fix-v1-1-3a2d4392d117%40uniontech.com

-- 
Luiz Augusto von Dentz