linux-kernel - [PATCH v2 0/2] printk: CPU backtrace not printing on panic

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Message-Id: <20240803080444.221427-1-takakura@valinux.co.jp>
Date: Sat,  3 Aug 2024 17:04:44 +0900
From: takakura@...inux.co.jp
To: pmladek@...e.com,
	rostedt@...dmis.org,
	john.ogness@...utronix.de,
	senozhatsky@...omium.org,
	akpm@...ux-foundation.org,
	bhe@...hat.com,
	lukas@...ner.de,
	wangkefeng.wang@...wei.com,
	ubizjak@...il.com,
	feng.tang@...el.com,
	j.granados@...sung.com,
	stephen.s.brennan@...cle.com
Cc: linux-kernel@...r.kernel.org,
	nishimura@...inux.co.jp,
	taka@...inux.co.jp,
	Ryo Takakura <takakura@...inux.co.jp>
Subject: [PATCH v2 0/2] printk: CPU backtrace not printing on panic

From: Ryo Takakura <takakura@...inux.co.jp>

Hi! 

This patchset fixes 2 issues on CPU backtrace during panic. The first 
issue was pointed out by John [1].

(1) The usual(non-panic context) flushing of backtraces written into 
ringbuffer does not work during panic as non-panicked CPUs can't do the 
flushing themselves.

(2) CPU backtrace triggered during panic has stopped working since the 
commit 779dbc2e78d7 ("printk: Avoid non-panic CPUs writing to ringbuffer") 
as it disabled non-panicked cpus writing into ringbuffer after panic.

Sincerely,
Ryo Takakura

---

Changes since V1:
[1] https://lore.kernel.org/all/20240729114601.176047-1-takakura@valinux.co.jp/T/

- Thanks for the feedbacks by Petr and John.
- Fix the issue (1) seperately from original patch.
- Fix the issue (2) by allowing non-panicked CPUs to write into ringbuffer 
while CPU backtrace is triggered as suggested by Petr.

---

Ryo Takakura (2):
  Handle flushing of CPU backtraces during panic
  Allow cpu backtraces to be written into ringbuffer during panic

 include/linux/panic.h  | 1 +
 kernel/panic.c         | 9 ++++++++-
 kernel/printk/printk.c | 2 +-
 3 files changed, 10 insertions(+), 2 deletions(-)

-- 
2.34.1