Hi,
This is v4 of a series to implement threaded console printing
as well as some other minor pieces (such as proc and sysfs
recognition of nbcon consoles). v3 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 v3:
- In nbcon_enter_unsafe()/nbcon_exit_unsafe(), clear the write
context buffer if ownership was lost.
- In nbcon_emit_next_record(), add a comment that lost
ownership is detected when entering unsafe.
- For patch 02/17 ("printk: Fail pr_flush() if before
SYSTEM_SCHEDULING"), update commit message as requested.
- For patch 04/17 ("printk: nbcon: Add context to usable() and
emit()"), remove redundant error checking from
nbcon_emit_next_record().
- In nbcon_alloc(), initialize @nbcon_seq to the highest
possible value to avoid printing until the correct value is
known.
- In nbcon_emit_next_record(), add a comment reminding that
write_thread() is mandatory and already checked.
- In nbcon_alloc(), use WARN_ON() instead of a custom error
message.
- Relocate nbcon_atomic_emit_one() above nbcon_kthread_func()
so that it can be shared.
- Rename nbcon_wake_kthreads() to nbcon_kthreads_wake().
- Move device_lock()/device_unlock() usage inside
nbcon_emit_one().
- Use nbcon_emit_one() for nbcon_legacy_emit_next_record() and
nbcon_kthread_func().
- For patch 08/17 ("printk: nbcon: Use thread callback if in
task context for legacy"), mention in the commit message
about consolidating legacy and kthread printing.
- In console_is_usable(), add a comment explaining why
@printk_kthreads_running is not checked for !use_atomic.
- In nbcon_atomic_flush_pending_con() and
nbcon_device_release(), check for !ft.nbcon_offload to
continue flushing.
- In console_start(), find out if it is an nbcon console while
holding the console_list_lock. This avoids the need to take
the console_srcu_read_unlock later in the function.
- In is_printk_deferred(), check force_legacy_kthread().
John Ogness
[0] https://lore.kernel.org/lkml/20240722171939.3349410-1-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 | 497 +++++++++++++++++++++++++-----
kernel/printk/printk.c | 467 ++++++++++++++++++++++++----
kernel/printk/printk_ringbuffer.h | 2 +
kernel/printk/printk_safe.c | 4 +-
8 files changed, 976 insertions(+), 133 deletions(-)
base-commit: 59cd94ef80094857f0d0085daa2e32badc4cddf4
--
2.39.2
