[RFC][PATCHv2 0/4] less deadlock prone serial consoles

[Sergey Senozhatsky]

	Hello,


	RFC


	The patch set reduces the number of ways serial consoles
can deadlock the system, including the recently reported deadlock
in panic().

The test scenario I ran on my x86_64 box:
- panic() the system while one of the CPUs holds 8250's
  uart_port->lock.

Test results:

	base		|	patched
	-----------------------------------------
	deadlock	|	flush logbuf
			|	reboot the system

To keep the cover letter short, please find full description in
commit messages.

P.S. since this is RFC I modify only 8250 serial driver.

Sergey Senozhatsky (4):
  panic: avoid deadlocks in re-entrant console drivers
  printk: move printk_safe macros to printk header
  seial: introduce uart_port locking helpers
  tty: 8250: switch to uart_port locking helpers

 drivers/tty/serial/8250/8250_core.c |  8 +--
 drivers/tty/serial/8250/8250_dma.c  |  4 +-
 drivers/tty/serial/8250/8250_port.c | 81 +++++++++++++----------------
 include/linux/printk.h              | 40 ++++++++++++++
 include/linux/serial_core.h         | 48 +++++++++++++++++
 kernel/panic.c                      |  6 +++
 kernel/printk/internal.h            | 37 -------------
 kernel/printk/printk_safe.c         |  6 ++-
 8 files changed, 141 insertions(+), 89 deletions(-)

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2.19.1