[PATCH] kernel: time: timer.c: use __fls in apply_slack()

From	Rasmus Villemoes <linux@rasmusvillemoes.dk>
Newsgroups	linux.kernel
Subject	[PATCH] kernel: time: timer.c: use __fls in apply_slack()
Date	2015-10-02 09:50 +0200
Message-ID	<qf3gm-5mM-21@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

Show all headers | View raw

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 23 bytes of the only caller, mod_timer().

This also gets rid of Coverity CID 1192106, but that is a false
positive: Coverity is not aware that mask != 0 implies that
find_last_bit will not return BITS_PER_LONG.

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

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 84190f02b521..71eb089d1030 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -867,7 +867,7 @@ 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;
 
-- 
2.1.3

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[PATCH] kernel: time: timer.c: use __fls in apply_slack() Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2015-10-02 09:50 +0200

csiph-web