staging: wfx: fix potential deadlock in wfx_tx_flush()

wfx_tx_flush() wait there are no more frame in device buffer. However,
this event may never happens since wfx_tx_flush() don't forbid to
enqueue new frames.

Note that wfx_tx_flush() should only ensure that all frames currently in
hardware queues are sent. So the current code is more restrictive that
it should.

Note that wfx_tx_flush() release the lock before to return while
wfx_tx_lock_flush() keep the lock.

Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200401110405.80282-31-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/wfx/queue.c b/drivers/staging/wfx/queue.c
index d4302a30dc41c7ba84cf840b0c665c659f5dee9b..e6d7d0e45156ecdc8c9ba6717e4dd8a2feba1ca5 100644 (file)
--- a/drivers/staging/wfx/queue.c
+++ b/drivers/staging/wfx/queue.c
@@ -36,6 +36,7 @@ void wfx_tx_flush(struct wfx_dev *wdev)
        if (wdev->chip_frozen)
                return;
 
+       wfx_tx_lock(wdev);
        mutex_lock(&wdev->hif_cmd.lock);
        ret = wait_event_timeout(wdev->hif.tx_buffers_empty,
                                 !wdev->hif.tx_buffers_used,
@@ -54,6 +55,7 @@ void wfx_tx_flush(struct wfx_dev *wdev)
                wdev->chip_frozen = 1;
        }
        mutex_unlock(&wdev->hif_cmd.lock);
+       wfx_tx_unlock(wdev);
 }
 
 void wfx_tx_lock_flush(struct wfx_dev *wdev)