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From:   Sumit Garg <sumit.garg@linaro.org>
To:     daniel.thompson@linaro.org
Cc:     kgdb-bugreport@lists.sourceforge.net, jason.wessel@windriver.com,
        dianders@chromium.org, pmladek@suse.com,
        sergey.senozhatsky@gmail.com, gregkh@linuxfoundation.org,
        jslaby@suse.com, linux-kernel@vger.kernel.org,
        Sumit Garg <sumit.garg@linaro.org>
Subject: [PATCH v6 0/4] kdb: Improve console handling
Date:   Thu,  4 Jun 2020 15:31:15 +0530
Message-Id: <1591264879-25920-1-git-send-email-sumit.garg@linaro.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

This patch-set is aimed to improve console handling especially when kdb
operates in NMI context.

Brief description of enhancements:
- Add status check for console prior to invoking corresponding handler.
- Fixup to avoid possible deadlock in NMI context due to usage of locks
  in the console handlers.
- Prefer usage of polling I/O driver mode (lockless APIs) over invocation
  of console handlers.

Changes in v6:
- Replace early_con -> kgdboc_earlycon_io_ops.cons.
- Added Petr's review tag on patch #1, #2 and #3.
- Drop Doug's review tag from patch #4 due to early_con changes which I
  think needs a re-review.

Changes in v5:
- Rebased on top of tags/kgdb-5.8-rc1.
- Get rid of kdb_io_write().
- Fixed issue reported by kbuild test robot.
- Remove is_console from kgdboc_earlycon_io_ops as well.
- Misc. comments.
- Added Doug's review tag.

Changes in v4:
- Use dbg_io_ops->write_char() directly instead of passing it as a
  function pointer.
- Use "struct console" rather than "struct tty_driver" for comparison.
- Make commit descriptions and comments more informative.
- Add review tag for patch #2.

Changes in v3:
- Split patch to have separate patch for console status check.
- New patch to re-factor kdb message emit code.
- New patch to prefer polling I/O over console mode.
- Add code comments to describe usage of oops_in_progress.

Changes in v2:
- Use oops_in_progress directly instead of bust_spinlocks().

Sumit Garg (4):
  kdb: Re-factor kdb_printf() message write code
  kdb: Check status of console prior to invoking handlers
  kdb: Make kdb_printf() console handling more robust
  kdb: Switch to use safer dbg_io_ops over console APIs

 drivers/tty/serial/kgdb_nmi.c |  2 +-
 drivers/tty/serial/kgdboc.c   | 32 +++++++++----------
 drivers/usb/early/ehci-dbgp.c |  3 +-
 include/linux/kgdb.h          |  5 ++-
 kernel/debug/kdb/kdb_io.c     | 72 ++++++++++++++++++++++++++-----------------
 5 files changed, 64 insertions(+), 50 deletions(-)

-- 
2.7.4