Hi, This is v2 of a series to implement threaded console printing as well as some other minor pieces (such as proc and sysfs support). This series is only a subset of the original v1 [0]. In particular, this series represents patches 11, 12, 15 of the v1 series. For information about the motivation of the nbcon consoles, please read the cover letter of v1. 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 "threadprintk" boot argument to force threading of legacy consoles. - Implement nbcon support for proc and sysfs console-related files. - Provide a new helper function nbcon_reacquire() 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. Also note that the first 3 patches of the series are either already mainline or are queued for 6.11. They are included in this series for completeness when applied to the printk for-next branch. Much has changed since v1 and the patches no longer correlate 1:1. Here is an attempt to list the changes: - Implement a special dedicated thread to force threading of legacy console drivers. - Add "threadprintk" boot argument to force threading of legacy console drivers. (For PREEMPT_RT, this is automatically enabled.) - Add sparse notation for console_srcu_read_lock/unlock(). - Define a dedicated wait queue for the legacy thread. - Stop threads on shutdown/reboot for a clean transition to atomic printing. - Print a replay message when a higher priority printer context takes over another printer context. - Reset lockdep context for legacy printing on !PREEMPT_RT to avoid false positive lockdep splats. - Use write_thread() callback if printing from console_flush_all() and @do_cond_resched is 1. - Do not allocate separate pbufs for printing threads. Use the same pbufs that the atomic printer uses. - Wake printing threads without considering nbcon lock state. - Implement rcuwait_has_sleeper() to check for waiting tasks instead of using a custom atomic variable @kthread_waiting. John Ogness [0] https://lore.kernel.org/lkml/20230302195618.156940-1-john.ogness@xxxxxxxxxxxxx John Ogness (13): printk: Atomic print in printk context on shutdown printk: nbcon: Add context to console_is_usable() printk: nbcon: Stop threads on shutdown/reboot printk: nbcon: Start printing threads printk: Provide helper for message prepending printk: nbcon: Show replay message on takeover printk: Add kthread for all legacy consoles proc: consoles: Add notation to c_start/c_stop proc: Add nbcon support for /proc/consoles tty: sysfs: Add nbcon support for 'active' printk: Provide threadprintk boot argument printk: Avoid false positive lockdep report for legacy printing printk: nbcon: Add function for printers to reacquire ownership Sreenath Vijayan (3): printk: Add function to replay kernel log on consoles tty/sysrq: Replay kernel log messages on consoles via sysrq printk: Rename console_replay_all() and update context Thomas Gleixner (2): printk: nbcon: Introduce printing kthreads printk: nbcon: Add printer thread wakeups .../admin-guide/kernel-parameters.txt | 12 + Documentation/admin-guide/sysrq.rst | 9 + drivers/tty/sysrq.c | 13 +- drivers/tty/tty_io.c | 9 +- fs/proc/consoles.c | 16 +- include/linux/console.h | 38 ++ include/linux/printk.h | 6 +- kernel/printk/internal.h | 55 +- kernel/printk/nbcon.c | 421 ++++++++++++++- kernel/printk/printk.c | 482 +++++++++++++++--- 10 files changed, 945 insertions(+), 116 deletions(-) base-commit: f3760c80d06a838495185c0fe341c043e6495142 -- 2.39.2
