[PATCH] kernel: timer.c: Small improvement in apply_slack()

From: Rasmus Villemoes
Date: Mon Jul 28 2014 - 10:49:20 EST

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@xxxxxxxxxxxxxxxxxx>
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;


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