Hi, This is v2 of a series to wire up the nbcon consoles so that they actually perform atomic printing. This series is only a subset of the original v1 [0]. In particular, this series represents patches 14 and 16-18 of the v1 series. For information about the motivation of the atomic consoles, please read the cover letter of v1. This series focuses on providing the functionality and marking of atomic printing sections as well as wiring up the nbcon atomic printing to the general console_flush_all() function. This series does _not_ include threaded printing or nbcon drivers. Those features will be added in separate follow-up series. Note that the behavior of atomic printing in priority-elevated atomic printing sections differs from the legacy consoles. With atomic printing, the full set of urgent messages (WARN/OOPS/PANIC) are first stored into the ringbuffer and then afterwards flushed. This makes sure the full backtraces are available in the ringbuffer, even if they do not make it out to the console(s). This is in accordance with what was discussed at LPC 2022 [1]. A lot has changed since v1 and the patches no longer correlate 1:1. Here is an attempt to list the changes: - Rather than flushing the full ringbuffer with one nbcon console before moving to the next nbcon console, adapt the same flushing strategy as the legacy consoles: rotation through the consoles, one record at a time. - Introduce nbcon_atomic_emit_one() to perform the "lock, emit one record, unlock" pattern. (This is only a helper function.) - Introduce nbcon_console_emit_next_record() to act as the nbcon variant of console_emit_next_record(). This allows straight forward integration of nbcon consoles into console_flush_all(). - nbcon_atomic_flush() no longer takes any arguments. These were awkward for the caller. The context object is now hidden from the caller. - Introduce __nbcon_atomic_flush_all() as an internal helper function in order to hide the ability to attempt unsafe hostile takeovers from outside nbcon.c. - For printk_trigger_flush(), migration is disabled instead of preemption. - Add atomic write enforcement to oops and lockdep. - Comments and kerneldoc updated. John Ogness [0] https://lore.kernel.org/lkml/20230302195618.156940-1-john.ogness@xxxxxxxxxxxxx [1] https://lore.kernel.org/lkml/875yheqh6v.fsf@xxxxxxxxxxxxxxxxxxxxx John Ogness (7): printk: Make console_is_usable() available to nbcon printk: Let console_is_usable() handle nbcon printk: Add @flags argument for console_is_usable() printk: nbcon: Wire up nbcon into console_flush_all() panic: Add atomic write enforcement to oops rcu: Add atomic write enforcement for rcu stalls lockdep: Add atomic write enforcement for lockdep splats Thomas Gleixner (4): printk: nbcon: Provide functions to mark atomic write sections printk: nbcon: Provide function for atomic flushing printk: nbcon: Wire up nbcon console atomic flushing panic: Add atomic write enforcement to warn/panic include/linux/console.h | 4 + include/linux/printk.h | 6 + kernel/locking/lockdep.c | 7 ++ kernel/panic.c | 66 +++++++++++ kernel/printk/internal.h | 37 ++++++ kernel/printk/nbcon.c | 246 ++++++++++++++++++++++++++++++++++++++- kernel/printk/printk.c | 67 +++++------ kernel/rcu/tree_stall.h | 6 + 8 files changed, 396 insertions(+), 43 deletions(-) base-commit: 9757acd0a700ba4a0d16dde4ba820eb052aba1a7 -- 2.39.2
