linux-kernel - [PATCH] kernel: timer.c: Small improvement in apply

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Date:	Mon, 28 Jul 2014 16:48:45 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel@...r.kernel.org,
	Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH] kernel: timer.c: Small improvement in apply_slack()

In apply_slack(), find_last_bit() is applied to a bitmask consisting
of precisely BITS_PER_LONG bits. Since mask is non-zero, we might as
well eliminate the function call and use __fls() directly. On x86_64,
this shaves 22 bytes of the only caller, mod_timer().

Found through Coverity CID 1192106, but that is a false positive,
since Coverity is not aware that mask != 0 implies that find_last_bit
will not return BITS_PER_LONG.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 kernel/timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/timer.c b/kernel/timer.c
index 3bb01a3..b7d1a1e 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -836,7 +836,7 @@ unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
 	if (mask == 0)
 		return expires;
 
-	bit = find_last_bit(&mask, BITS_PER_LONG);
+	bit = __fls(mask);
 
 	mask = (1UL << bit) - 1;
 
-- 
1.9.2

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