[PATCH printk v8 00/35] wire up write_atomic() printing

From: John Ogness
Date: Tue Aug 20 2024 - 02:30:32 EST


Hi,

This is v8 of a series to wire up the nbcon consoles so that
they actually perform printing using their write_atomic()
callback. v7 is here [0]. For information about the motivation
of the atomic consoles, please read the cover letter of v1 [1].

The main focus of this series:

- For nbcon consoles, always call write_atomic() directly from
printk() caller context for the panic CPU.

- For nbcon consoles, call write_atomic() when unlocking the
console lock.

- Only perform the console lock/unlock dance if legacy or boot
consoles are registered.

- For legacy consoles, if nbcon consoles are registered, do not
attempt to print from printk() caller context for the panic
CPU until nbcon consoles have had a chance to print the most
significant messages.

- Mark emergency sections. In these sections, every printk()
call will attempt to directly flush to the consoles using the
EMERGENCY priority.

This series does _not_ include threaded printing or nbcon
drivers. Those features will be added in separate follow-up
series.

The changes since v7:

- Change printk_get_console_flush_type() to set preferred flush
types.

- Change printk_get_console_flush_type() to also check for
legacy consoles before seting @legacy_direct.

- Change vprintk_emit() to hack the struct console_flush_type
for LOGLEVEL_SCHED rather than using local variables.

- Change console_cpu_notify() to also flush nbcon atomic
consoles.

- Remove unnecessary flush type check in
nbcon_atomic_flush_pending_con(). It is not needed until the
threaded series.

- Fix compiling issues related to @legacy_allow_panic_sync for
!CONFIG_PRINTK.

John Ogness

[0] https://lore.kernel.org/lkml/20240804005138.3722656-1-john.ogness@xxxxxxxxxxxxx
[1] https://lore.kernel.org/lkml/20230302195618.156940-1-john.ogness@xxxxxxxxxxxxx

John Ogness (30):
printk: Add notation to console_srcu locking
printk: nbcon: Consolidate alloc() and init()
printk: nbcon: Clarify rules of the owner/waiter matching
printk: nbcon: Remove return value for write_atomic()
printk: nbcon: Add detailed doc for write_atomic()
printk: nbcon: Add callbacks to synchronize with driver
printk: nbcon: Use driver synchronization while (un)registering
serial: core: Provide low-level functions to lock port
serial: core: Introduce wrapper to set @uart_port->cons
console: Improve console_srcu_read_flags() comments
nbcon: Add API to acquire context for non-printing operations
serial: core: Acquire nbcon context in port->lock wrapper
printk: nbcon: Do not rely on proxy headers
printk: Make console_is_usable() available to nbcon.c
printk: Let console_is_usable() handle nbcon
printk: Add @flags argument for console_is_usable()
printk: nbcon: Add helper to assign priority based on CPU state
printk: Track registered boot consoles
printk: nbcon: Use nbcon consoles in console_flush_all()
printk: Add is_printk_legacy_deferred()
printk: nbcon: Flush new records on device_release()
printk: Flush nbcon consoles first on panic
printk: nbcon: Add unsafe flushing on panic
printk: Avoid console_lock dance if no legacy or boot consoles
printk: Track nbcon consoles
printk: Coordinate direct printing in panic
printk: Add helper for flush type logic
panic: Mark emergency section in oops
rcu: Mark emergency sections in rcu stalls
lockdep: Mark emergency sections in lockdep splats

Petr Mladek (1):
printk: Properly deal with nbcon consoles on seq init

Sebastian Andrzej Siewior (1):
printk: Check printk_deferred_enter()/_exit() usage

Thomas Gleixner (3):
printk: nbcon: Provide function to flush using write_atomic()
printk: nbcon: Implement emergency sections
panic: Mark emergency section in warn

drivers/tty/serial/8250/8250_core.c | 6 +-
drivers/tty/serial/amba-pl011.c | 2 +-
drivers/tty/serial/serial_core.c | 16 +-
include/linux/console.h | 110 +++++-
include/linux/printk.h | 33 +-
include/linux/serial_core.h | 117 +++++-
kernel/locking/lockdep.c | 83 ++++-
kernel/panic.c | 9 +
kernel/printk/internal.h | 137 ++++++-
kernel/printk/nbcon.c | 556 +++++++++++++++++++++++++---
kernel/printk/printk.c | 251 ++++++++++---
kernel/printk/printk_ringbuffer.h | 2 +
kernel/printk/printk_safe.c | 23 +-
kernel/rcu/tree_exp.h | 7 +
kernel/rcu/tree_stall.h | 9 +
15 files changed, 1210 insertions(+), 151 deletions(-)


base-commit: bcc954c6caba01fca143162d5fbb90e46aa1ad80
--
2.39.2