linux-kernel - [RFC 18/60] sched: Fix return value of SCHED_WARN

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Message-Id: <20180907214047.26914-19-jschoenh@amazon.de>
Date:   Fri,  7 Sep 2018 23:40:05 +0200
From:   Jan H. Schönherr <jschoenh@...zon.de>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Jan H. Schönherr <jschoenh@...zon.de>,
        linux-kernel@...r.kernel.org
Subject: [RFC 18/60] sched: Fix return value of SCHED_WARN_ON()

SCHED_WARN_ON() is conditionally compiled depending on CONFIG_SCHED_DEBUG.
WARN_ON() and variants can be used in if() statements to take an action
in the unlikely case that the WARN_ON condition is true. This is supposed
to work independently of whether the warning is actually printed. However,
without CONFIG_SCHED_DEBUG, SCHED_WARN_ON() evaluates to false
unconditionally.

Change SCHED_WARN_ON() to not discard the WARN_ON condition, even without
CONFIG_SCHED_DEBUG, so that it can be used within if() statements as
expected.

Signed-off-by: Jan H. Schönherr <jschoenh@...zon.de>
---
 kernel/sched/sched.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 9ecbb57049a2..3e0ad36938fb 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -76,7 +76,7 @@
 #ifdef CONFIG_SCHED_DEBUG
 # define SCHED_WARN_ON(x)	WARN_ONCE(x, #x)
 #else
-# define SCHED_WARN_ON(x)	({ (void)(x), 0; })
+# define SCHED_WARN_ON(x)	({ unlikely(!!(x)); })
 #endif

 struct rq;
-- 
2.9.3.1.gcba166c.dirty