linux-kernel - [PATCH v3 11/20] ratelimit: Force re-initialization when rate-limiting re-enabled

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Message-Id: <20250425002826.3431914-11-paulmck@kernel.org>
Date: Thu, 24 Apr 2025 17:28:17 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: kernel-team@...a.com,
	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>,
	"Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH v3 11/20] ratelimit: Force re-initialization when rate-limiting re-enabled

Currently, rate limiting being disabled results in an immediate early
return with no state changes.  This can result in false-positive drops
when re-enabling rate limiting.  Therefore, mark the ratelimit_state
structure "uninitialized" when rate limiting is disabled.

Link: https://lore.kernel.org/all/fbe93a52-365e-47fe-93a4-44a44547d601@paulmck-laptop/
Link: https://lore.kernel.org/all/20250423115409.3425-1-spasswolf@web.de/
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Petr Mladek <pmladek@...e.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: Mateusz Guzik <mjguzik@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: John Ogness <john.ogness@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>
---
 lib/ratelimit.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/ratelimit.c b/lib/ratelimit.c
index 7a7ba4835639f..52aab9229ca50 100644
--- a/lib/ratelimit.c
+++ b/lib/ratelimit.c
@@ -35,11 +35,24 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func)
 	unsigned long flags;
 	int ret;
 
+	/*
+	 * Zero interval says never limit, otherwise, non-positive burst
+	 * says always limit.
+	 */
 	if (interval <= 0 || burst <= 0) {
 		ret = interval == 0 || burst > 0;
+		if (!(READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED) ||
+		    !raw_spin_trylock_irqsave(&rs->lock, flags)) {
+			if (!ret)
+				ratelimit_state_inc_miss(rs);
+			return ret;
+		}
+
+		/* Force re-initialization once re-enabled. */
+		rs->flags &= ~RATELIMIT_INITIALIZED;
 		if (!ret)
 			ratelimit_state_inc_miss(rs);
-		return ret;
+		goto unlock_ret;
 	}
 
 	/*
-- 
2.40.1