[PATCH printk v5 00/17] add threaded printing + the rest

[John Ogness]

Hi,

This is v5 of a series to implement threaded console printing
as well as some other minor pieces (such as proc and sysfs
recognition of nbcon consoles). v4 is here [0].

For information about the motivation of the nbcon consoles,
please read the cover letter of the original v1 [1].

This series provides the remaining pieces of the printk
rework. All other components are either already mainline or are
currently in linux-next. In particular this series does:

- Implement dedicated printing threads per nbcon console.

- Implement forced threading of legacy consoles for PREEMPT_RT.

- Implement nbcon support for proc and sysfs console-related
  files.

- Provide a new helper function nbcon_reacquire_nobuf() to
  allow nbcon console drivers to reacquire ownership.

Note that this series does *not* provide an nbcon console
driver. That will come in a follow-up series.

Here are the changes since v4:

- For nbcon_kthread_create(), add more explanations about the
  context and rules to the kerneldoc.

- In nbcon_alloc(), clear con->pbufs on failure.

- Remove legacy_kthread_wake() and add its functionality to
  wake_up_klogd_work_func() since it was the only call site.

- In console_start(), allow triggering the legacy loop if it is
  an nbcon. There might be a registered boot console.

- In __pr_flush(), add atomic flushing before wait loop.

- In console_try_replay_all(), add atomic flushing.

John Ogness

[0] https://lore.kernel.org/lkml/20240827044333.88596-1-john.ogness@xxxxxxxxxxxxx

[1] https://lore.kernel.org/lkml/20230302195618.156940-1-john.ogness@xxxxxxxxxxxxx

John Ogness (16):
  printk: nbcon: Add function for printers to reacquire ownership
  printk: Fail pr_flush() if before SYSTEM_SCHEDULING
  printk: Flush console on unregister_console()
  printk: nbcon: Add context to usable() and emit()
  printk: nbcon: Init @nbcon_seq to highest possible
  printk: nbcon: Relocate nbcon_atomic_emit_one()
  printk: nbcon: Use thread callback if in task context for legacy
  printk: nbcon: Rely on kthreads for normal operation
  printk: Provide helper for message prepending
  printk: nbcon: Show replay message on takeover
  proc: consoles: Add notation to c_start/c_stop
  proc: Add nbcon support for /proc/consoles
  tty: sysfs: Add nbcon support for 'active'
  printk: Implement legacy printer kthread for PREEMPT_RT
  printk: nbcon: Assign nice -20 for printing threads
  printk: Avoid false positive lockdep report for legacy printing

Thomas Gleixner (1):
  printk: nbcon: Introduce printer kthreads

 drivers/tty/tty_io.c              |   2 +-
 fs/proc/consoles.c                |   7 +-
 include/linux/console.h           |  48 +++
 kernel/printk/internal.h          |  82 ++++-
 kernel/printk/nbcon.c             | 504 +++++++++++++++++++++++++-----
 kernel/printk/printk.c            | 465 ++++++++++++++++++++++++---
 kernel/printk/printk_ringbuffer.h |   2 +
 kernel/printk/printk_safe.c       |   4 +-
 8 files changed, 981 insertions(+), 133 deletions(-)


base-commit: 59cd94ef80094857f0d0085daa2e32badc4cddf4
-- 
2.39.2