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 <abrodkin@synopsys.com> Cc: Jiri Slaby <jslaby@suse.com> Cc: Peter Hurley <peter@hurleysoftware.com> Cc: Phillip Raffeck <phillip.raffeck@fau.de> Cc: Anton Wuerfel <anton.wuerfel@fau.de> Cc: "Matwey V. Kornilov" <matwey@sai.msu.ru> Cc: Yegor Yefremov <yegorslists@googlemail.com> Cc: Thor Thayer <tthayer@opensource.altera.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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