linux-kernel - [PATCH v2 ratelimit 11/14] ratelimit: Force re-initialization when rate-limiting re-enabled

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Message-Id: <20250418171359.1187719-11-paulmck@kernel.org>
Date: Fri, 18 Apr 2025 10:13:56 -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 v2 ratelimit 11/14] 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.

Additionally, interpret non-positive ->burst to unconditionally force
rate limiting.  When ->burst is positive, interpret non-positive interval
to unconditionally disable rate limiting.

Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: Mateusz Guzik <mjguzik@...il.com>
Cc: Petr Mladek <pmladek@...e.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: John Ogness <john.ogness@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>
---
 lib/ratelimit.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/lib/ratelimit.c b/lib/ratelimit.c
index 04f16b8e24575..6c639ab6489d5 100644
--- a/lib/ratelimit.c
+++ b/lib/ratelimit.c
@@ -35,8 +35,20 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func)
 	unsigned long flags;
 	int ret;
 
-	if (!interval || !burst)
-		return 1;
+	/*
+	 * Non-positive burst says always limit, otherwise, non-positive
+	 * interval says never limit.
+	 */
+	if (interval <= 0 || burst <= 0) {
+		ret = burst > 0;
+		if (!(READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED) ||
+		    !raw_spin_trylock_irqsave(&rs->lock, flags))
+			return ret;
+		
+		/* Force re-initialization once re-enabled. */
+		rs->flags &= ~RATELIMIT_INITIALIZED;
+		goto unlock_ret;
+	}
 
 	/*
 	 * If we contend on this state's lock then just check if
-- 
2.40.1