linux-kernel - [PATCH v6 0/3] ratelimit: Add tests for lib/ratelimit.c

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Message-ID: <d1007957-97ff-4f6f-92ac-606f68c65dfa@paulmck-laptop>
Date: Wed, 9 Jul 2025 11:00:49 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Kuniyuki Iwashima <kuniyu@...zon.com>,
	Mateusz Guzik <mjguzik@...il.com>, Petr Mladek <pmladek@...e.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	John Ogness <john.ogness@...utronix.de>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Jon Pan-Doh <pandoh@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Karolina Stolarek <karolina.stolarek@...cle.com>
Subject: [PATCH v6 0/3] ratelimit: Add tests for lib/ratelimit.c

Hello!

This v6 series adds a simple "smoke" test along with a simple stress test:

1.	Add trivial kunit test for ratelimit.

2.	Make the ratelimit test more reliable, courtesy of Petr Mladek.

3.	Add stress test for ratelimit.

							Thanx, Paul

Changes since v5:

o	Drop patches that have since been accepted into mainline.

o	Add Petr Mladek's patch improving the reliability of the simple
	test.

Changes since v4:

o	Add a simple stress test.

o	Move the tests to the end of the series for bisectability.

o	Add Reviewed-by tags.

Changes since v3:

o	Correctly handle zero-initialized ratelimit_state structures,
	being careful to avoid acquiring the uninitialized ->lock.

o	Remove redundant checks of the "burst" local variable.

o	Add Reviewed-by tags.

Changes since v2:

o	Apply feedback from Bert Karwatzki, Srikanth Aithal, and Mark
	Brown, fixing a hang that happened on some systems.

o	Applied Reviewed-by tags and added links.

o	Added a prototype patch from Petr Mladek that splats if either
	interval or burst are negative.

o	Added several commits that simplify the code.

Changes since v1 (RFC):

o	Switch from lockless fastpath to carrying out needed updates
	upon trylock failure, per Petr Mladek feedback.  This greatly
	simplifies the code and is a much smaller change from the
	current code.  There is a small performance penalty compared to
	the lockless fastpath, but not enough to matter.

o	Never unconditionally acquire the lock, again per Petr Mladek
	feedback.

o	Better define effects of non-positive burst values (always
	ratelimit) and non-positive interval values (never ratelimit
	when the burst value is positive).

o	The changes from Petr's original are supplied as five incremental
	patches, but could easily be folded into Petr's original if
	desired.  (Left to my lazy self, they stay as-is.)

------------------------------------------------------------------------

 b/lib/Kconfig.debug          |   11 +++++
 b/lib/tests/Makefile         |    1 
 b/lib/tests/test_ratelimit.c |   79 +++++++++++++++++++++++++++++++++++++++++++
 lib/tests/test_ratelimit.c   |   77 ++++++++++++++++++++++++++++++++++++++---
 4 files changed, 162 insertions(+), 6 deletions(-)