linux-kernel - [PATCH] ratelimit: fix WARN_ON

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Message-Id: <20161215093224.23126-1-jslaby@suse.cz>
Date:   Thu, 15 Dec 2016 10:32:24 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH] ratelimit: fix WARN_ON_RATELIMIT return value

The macro is to be used similarly as WARN_ON as:
  if (WARN_ON_RATELIMIT(condition, state))
	do_something();

One would expect only 'condition' to affect the 'if', but
WARN_ON_RATELIMIT does internally only:
  WARN_ON((condition) && __ratelimit(state))

So the 'if' is affected by the ratelimiting state too. Fix this by
returning 'condition' in any case.

Note that nobody uses WARN_ON_RATELIMIT yet, so there is nothing to
worry about. But I was about to use it and was a bit surprised.

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 include/linux/ratelimit.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/ratelimit.h b/include/linux/ratelimit.h
index 57c9e0622a38..56375edf2ed2 100644
--- a/include/linux/ratelimit.h
+++ b/include/linux/ratelimit.h
@@ -77,8 +77,11 @@ extern int ___ratelimit(struct ratelimit_state *rs, const char *func);
 
 #ifdef CONFIG_PRINTK
 
-#define WARN_ON_RATELIMIT(condition, state)			\
-		WARN_ON((condition) && __ratelimit(state))
+#define WARN_ON_RATELIMIT(condition, state)	({		\
+	bool __rtn_cond = !!(condition);			\
+	WARN_ON(__rtn_cond && __ratelimit(state));		\
+	__rtn_cond;						\
+})
 
 #define WARN_RATELIMIT(condition, format, ...)			\
 ({								\
-- 
2.11.0