serial: 8250_port: Remove dangerous pr_debug()

With CONFIG_DYNAMIC_DEBUG if dyndbg enables debug output in
8250_port.c deadlock happens inevitably on UART IRQ handling.

That's the problematic execution path:
---------------------------->8------------------------
UART IRQ:
  serial8250_interrupt() ->
    serial8250_handle_irq(): lock "port->lock" ->
      pr_debug() ->
        serial8250_console_write(): bump in locked "port->lock".

      OR (if above pr_debug() gets removed):
      serial8250_tx_chars() ->
        pr_debug() ->
          serial8250_console_write(): bump in locked "port->lock".
---------------------------->8------------------------

So let's get rid of those not that much useful debug entries.

Discussed problem could be easily reproduced with QEMU for x86_64.
As well as this fix could be mimicked with muting of dynamic debug for
the problematic lines as simple as:
---------------------------->8------------------------
dyndbg="+p; file 8250_port.c line 1756 -p; file 8250_port.c line 1822 -p"
---------------------------->8------------------------

Signed-off-by: Alexey Brodkin <[email protected]>
Cc: Jiri Slaby <[email protected]>
Cc: Peter Hurley <[email protected]>
Cc: Phillip Raffeck <[email protected]>
Cc: Anton Wuerfel <[email protected]>
Cc: "Matwey V. Kornilov" <[email protected]>
Cc: Yegor Yefremov <[email protected]>
Cc: Thor Thayer <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions