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

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Message-Id: <20181016050428.17966-1-sergey.senozhatsky@gmail.com>
Date:   Tue, 16 Oct 2018 14:04:24 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Wang <wonderfly@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Jiri Slaby <jslaby@...e.com>,
        Peter Feiner <pfeiner@...gle.com>,
        linux-serial@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [RFC][PATCHv2 0/4] less deadlock prone serial consoles

	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(-)

-- 
2.19.1