[PATCH v5 0/4] kdb: Improve console handling

[Sumit Garg]

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 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   |  6 ++--
 drivers/usb/early/ehci-dbgp.c |  3 +-
 include/linux/kgdb.h          |  5 ++-
 kernel/debug/kdb/kdb_io.c     | 72 ++++++++++++++++++++++++++-----------------
 5 files changed, 51 insertions(+), 37 deletions(-)

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2.7.4