nci_close_device() flushes rx_wq and tx_wq while holding req_lock. This causes a circular locking dependency because nci_rx_work() running on rx_wq can end up taking req_lock too: nci_rx_work -> nci_rx_data_packet -> nci_data_exchange_complete -> __sk_destruct -> rawsock_destruct -> nfc_deactivate_target -> nci_deactivate_target -> nci_request -> mutex_lock(&ndev->req_lock) Move the flush of rx_wq after req_lock has been released. This should safe (I think) because NCI_UP has already been cleared and the transport is closed, so the work will see it and return -ENETDOWN. NIPA has been hitting this running the nci selftest with a debug kernel on roughly 4% of the runs. Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation") Signed-off-by: Jakub Kicinski --- CC: ian.ray@gehealthcare.com CC: ilane@ti.com CC: linville@tuxdriver.com --- net/nfc/nci/core.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/net/nfc/nci/core.c b/net/nfc/nci/core.c index 43d871525dbc..5f46c4b5720f 100644 --- a/net/nfc/nci/core.c +++ b/net/nfc/nci/core.c @@ -579,8 +579,7 @@ static int nci_close_device(struct nci_dev *ndev) skb_queue_purge(&ndev->rx_q); skb_queue_purge(&ndev->tx_q); - /* Flush RX and TX wq */ - flush_workqueue(ndev->rx_wq); + /* Flush TX wq, RX wq flush can't be under the lock */ flush_workqueue(ndev->tx_wq); /* Reset device */ @@ -592,13 +591,13 @@ static int nci_close_device(struct nci_dev *ndev) msecs_to_jiffies(NCI_RESET_TIMEOUT)); /* After this point our queues are empty - * and no works are scheduled. + * rx work may be running but will see that NCI_UP was cleared */ ndev->ops->close(ndev); clear_bit(NCI_INIT, &ndev->flags); - /* Flush cmd wq */ + /* Flush cmd and tx wq */ flush_workqueue(ndev->cmd_wq); timer_delete_sync(&ndev->cmd_timer); @@ -613,6 +612,9 @@ static int nci_close_device(struct nci_dev *ndev) mutex_unlock(&ndev->req_lock); + /* rx_work may take req_lock via nci_deactivate_target */ + flush_workqueue(ndev->rx_wq); + return 0; } -- 2.53.0