linux-kernel - [PATCH v3 0/2] Reduce CPU consumption after panic

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Message-ID: <20250429150638.1446781-1-carlos.bilbao@kernel.org>
Date: Tue, 29 Apr 2025 10:06:36 -0500
From: carlos.bilbao@...nel.org
To: tglx@...utronix.de,
	seanjc@...gle.com,
	jan.glauber@...il.com
Cc: bilbao@...edu,
	pmladek@...e.com,
	akpm@...ux-foundation.org,
	jani.nikula@...el.com,
	linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org,
	takakura@...inux.co.jp,
	john.ogness@...utronix.de,
	Carlos Bilbao <carlos.bilbao@...nel.org>
Subject: [PATCH v3 0/2] Reduce CPU consumption after panic

From: Carlos Bilbao <carlos.bilbao@...nel.org>

Provide a priority-based mechanism to set the behavior of the kernel at
the post-panic stage -- the current default is a waste of CPU except for
cases with console that generate insightful output.

In v1 cover letter [1], I illustrated the potential to reduce unnecessary
CPU resources with an experiment with VMs, reducing more than 70% of CPU
usage. The main delta of v2 [2] was that, instead of a weak function that
archs can overwrite, we provided a flexible priority-based mechanism
(following suggestions by Sean Christopherson), panic_set_handling().

Compared to v2 [2], the main changes in this third version are that (1) we
don't set a default function for panic_halt() and (2) we provide a comment
for the x86 implementation describing the check for console.

[1] https://lore.kernel.org/all/20250326151204.67898-1-carlos.bilbao@kernel.org/
[2] https://lore.kernel.org/all/20250428215952.1332985-1-carlos.bilbao@kernel.org/

Carlos:
  panic: Allow for dynamic custom behavior after panic
  x86/panic: Add x86_panic_handler as default post-panic behavior

---
 arch/x86/kernel/setup.c | 17 +++++++++++++++++
 include/linux/panic.h   |  2 ++
 kernel/panic.c          | 22 ++++++++++++++++++++++
 3 files changed, 41 insertions(+)