Re: [PATCH 1/3] serial: 8250: unlock port for uart_write_wakeup()

On 07/30/2015 06:54 PM, John Ogness wrote:
> uart_write_wakeup() should be called without holding the port lock.
> Otherwise a possible recursive spinlock issue can occur, such as
> the following callchain:
>
> 8250_core.c:serial8250_tx_chars() - called with port locked
> serial_core.c:uart_write_wakeup()
> tty_io.c:tty_wakeup()
> st_core.c:st_tty_wakeup()
> st_core.c:st_tx_wakeup()
> st_core.c:st_int_write()
> serial_core.c:uart_write() - locks port

NAK.

This is a bug in the N_TI_WL line discipline, specifically in the
st_tx_wakeup() function, which cannot perform the write synchronously.

This is a common line discipline bug, and typically fixed by performing
the wakeup operations from a kworker instead.

Regards,
Peter Hurley
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