linux-kernel - [PATCH printk v1 0/2] Fix ABBA deadlock for legacy printing with cpu

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Message-Id: <20241209111746.192559-1-john.ogness@linutronix.de>
Date: Mon,  9 Dec 2024 12:23:44 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org,
	Rik van Riel <riel@...riel.com>,
	Omar Sandoval <osandov@...a.com>
Subject: [PATCH printk v1 0/2] Fix ABBA deadlock for legacy printing with cpu_sync

Hi,

An RFC patch [0] was posted to fix an ABBA deadlock related to
nmi_backtrace() and dump_stack_lvl(). However, the underlying
problem was trying to perform legacy printing while holding the
printk_cpu_sync.

This series causes legacy printing to defer when holding the
printk_cpu_sync.

The first patch in the series is not necessary for the deadlock
fix, but was a redundancy I noticed while working on the series.

John Ogness

[0] https://lore.kernel.org/lkml/20240715232052.73eb7fb1@imladris.surriel.com

John Ogness (2):
  printk: Remove redundant deferred check in vprintk()
  printk: Defer legacy printing when holding printk_cpu_sync

 kernel/printk/internal.h    |  6 ++++++
 kernel/printk/printk.c      |  5 +++++
 kernel/printk/printk_safe.c | 16 ++++++----------
 3 files changed, 17 insertions(+), 10 deletions(-)

base-commit: 4022ef25504db2fb79a2acac0afe9bac934f8dd6
-- 
2.39.5