[PATCH] Bluetooth: btmtksdio: fix infinite loop in btmtksdio_txrx_work()

[Sergey Senozhatsky]

Every once in a while we see a hung btmtksdio_flush() task:

 INFO: task kworker/u17:0:189 blocked for more than 122 seconds.
 __cancel_work_timer+0x3f4/0x460
 cancel_work_sync+0x1c/0x2c
 btmtksdio_flush+0x2c/0x40
 hci_dev_open_sync+0x10c4/0x2190
 [..]

It all boils down to incorrect time_is_before_jiffies() usage in
btmtksdio_txrx_work().  The btmtksdio_txrx_work() loop is expected
to be terminated if running for longer than 5*HZ.  However the
timeout check is twisted:  time_is_before_jiffies(old_jiffies + 5*HZ)
evaluates to true when old_jiffies + 5*HZ is in the past i.e. when a
timeout has occurred.  Using OR with time_is_before_jiffies(txrx_timeout)
means that:
- before the 5-second timeout: the condition is `int_status || false`,
  so it loops as long as there are pending interrupts.
- after the 5-second timeout: the condition becomes `int_status || true`,
  which is always true.

When the loop becomes infinite btmtksdio_txrx_work() loop never
terminates and never releases the SDIO host.

Fix loop termination condition to actually enforce a 5*HZ timeout.

Fixes: 26270bc189ea4 ("Bluetooth: btmtksdio: move interrupt service to work")
Cc: stable at vger.kernel.org
Signed-off-by: Sergey Senozhatsky <senozhatsky at chromium.org>
---
 drivers/bluetooth/btmtksdio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btmtksdio.c b/drivers/bluetooth/btmtksdio.c
index 5b0fab7b89b5..c6f80c419e90 100644
--- a/drivers/bluetooth/btmtksdio.c
+++ b/drivers/bluetooth/btmtksdio.c
@@ -620,7 +620,7 @@ static void btmtksdio_txrx_work(struct work_struct *work)
 			if (btmtksdio_rx_packet(bdev, rx_size) < 0)
 				bdev->hdev->stat.err_rx++;
 		}
-	} while (int_status || time_is_before_jiffies(txrx_timeout));
+	} while (int_status && time_is_after_jiffies(txrx_timeout));
 
 	/* Enable interrupt */
 	if (bdev->func->irq_handler)
-- 
2.54.0.1064.gd145956f57-goog