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printk: Update the printk series to 6.6-rt-stable

Derek Barbosa requested to merge debarbos/centos-stream-9:andrew_tty into main

Upstream Status: https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git/

JIRA: https://issues.redhat.com/browse/RHEL-3987

JIRA: https://issues.redhat.com/browse/RHEL-24205

This series updates the CentOS Stream 9 Kernels TTY Layer to 6.7, and updates printk to 6.6-stable-rt.

After a series of introduced regressions with the older printk NOBKL atomic console implementation (circa LPC-dublin) [0][1][2], the KRTS team has been targeting the the newer NBCON atomic console printk rewrite, which aims to resolve the problems introduced from other implementations. Mainly, NBCON addresses the issue of deadlocks introduced from unsafe contexts, panics, nested NMIs, and other oddities caused by console lock contention.

However, as the newer upstream nbcon implementation is dependent on newer additions to the TTY subsystem, such as updates to UART port lock wrappers, 8250 changes, and additions to serial_core, the printk update requires a substantial update to the TTY layer.

This MR will also facilitate TTY, nbcon and printk updates for the foreseeable future, as newer changes will be based on the current UART Port lock wrappers present in 6.6+ kernels.

This MR effectively undoes the TTY/printk PREEMPT_RT bits responsible for the older printk implementation, pulls up the TTY layer to 6.7, and applies the 6.6-stable-rt (as 6.7.y-rt is now considered 'stale') printk changes (with some minor hunks brought in for panic.c, RCU, and lockdep).

[0] https://issues.redhat.com/browse/RHEL-9380

[1] https://issues.redhat.com/browse/RHEL-15897

[2] https://issues.redhat.com/browse/RHEL-17709

Signed-off-by: Andrew Halaney ahalaney@redhat.com

Signed-off-by: Derek Barbosa debarbos@redhat.com

Edited by Derek Barbosa

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