linux-kernel - [GIT PULL] printk for 6.9

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Date: Tue, 12 Mar 2024 15:54:57 +0100
From: Petr Mladek <pmladek@...e.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	John Ogness <john.ogness@...utronix.de>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Thomas Gleixner <tglx@...utronix.de>, Jan Kara <jack@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: [GIT PULL] printk for 6.9

Hi Linus,

please pull the latest printk changes from

  git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git tags/printk-for-6.9

========================================

Printk changes for 6.9 improve the behavior during panic. The issues were
found when testing the ongoing changes introducing atomic consoles and
printk kthreads.

- pr_flush() has to wait for the last reserved record instead
  of the last finalized one. Note that records are finalized
  in random order when generated by more CPUs in parallel.

- Ignore non-finalized records during panic(). Messages printed
  on panic-CPU are always finalized. Messages printed by other
  CPUs might never be finalized when the CPUs get stopped.

- Block new printk() calls on non-panic CPUs completely. Backtraces
  are printed before entering the panic mode. Later messages
  would just mess information printed by the panic CPU.

- Do not take console_lock in console_flush_on_panic() at all.
  The original code did try_lock()/console_unlock(). The unlock part
  might cause a deadlock when panic() happened in a scheduler code.

- Fix conversion of 64-bit sequence number for 32-bit atomic
  operations.

----------------------------------------------------------------
John Ogness (12):
      printk: nbcon: Relocate 32bit seq macros
      printk: Use prb_first_seq() as base for 32bit seq macros
      printk: ringbuffer: Do not skip non-finalized records with prb_next_seq()
      printk: ringbuffer: Clarify special lpos values
      printk: For @suppress_panic_printk check for other CPU in panic
      printk: Add this_cpu_in_panic()
      printk: ringbuffer: Cleanup reader terminology
      printk: Wait for all reserved records with pr_flush()
      printk: ringbuffer: Skip non-finalized records in panic
      printk: Avoid non-panic CPUs writing to ringbuffer
      panic: Flush kernel log buffer at the end
      dump_stack: Do not get cpu_sync for panic CPU

Petr Mladek (1):
      printk: Disable passing console lock owner completely during panic()

Sebastian Andrzej Siewior (1):
      printk: Adjust mapping for 32bit seq macros

 include/linux/printk.h            |   2 +
 kernel/panic.c                    |   8 +
 kernel/printk/nbcon.c             |  41 +----
 kernel/printk/printk.c            | 101 +++++++-----
 kernel/printk/printk_ringbuffer.c | 337 ++++++++++++++++++++++++++++++++------
 kernel/printk/printk_ringbuffer.h |  54 +++++-
 lib/dump_stack.c                  |  16 +-
 7 files changed, 420 insertions(+), 139 deletions(-)