linux-kernel - [PATCH v3 19/20] ratelimit: Use nolock_ret restructuring to collapse common case code

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Message-Id: <20250425002826.3431914-19-paulmck@kernel.org>
Date: Thu, 24 Apr 2025 17:28:25 -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 19/20] ratelimit: Use nolock_ret restructuring to collapse common case code

Now that unlock_ret releases the lock, then falls into nolock_ret, which
handles ->missed based on the value of ret, the common-case lock-held
code can be collapsed into a single "if" statement with a single-statement
"then" clause.

Yes, we could go further and just assign the "if" condition to ret,
but in the immortal words of MSDOS, "Are you sure?".

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 | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/lib/ratelimit.c b/lib/ratelimit.c
index 7bbc270b88e21..768f26790ea9a 100644
--- a/lib/ratelimit.c
+++ b/lib/ratelimit.c
@@ -88,17 +88,10 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func)
 			}
 		}
 	}
-	if (burst) {
-		int n_left = atomic_read(&rs->rs_n_left);
 
-		/* The burst might have been taken by a parallel call. */
-
-		if (n_left > 0) {
-			n_left = atomic_dec_return(&rs->rs_n_left);
-			if (n_left >= 0)
-				ret = 1;
-		}
-	}
+	/* Note that the burst might be taken by a parallel call. */
+	if (burst && atomic_read(&rs->rs_n_left) > 0 && atomic_dec_return(&rs->rs_n_left) >= 0)
+		ret = 1;
 
 unlock_ret:
 	raw_spin_unlock_irqrestore(&rs->lock, flags);
-- 
2.40.1