linux-kernel - [tip:timers/core] timers: Use __fls in apply

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Message-ID: <tip-9fc4468d546b6eb55b0aa5b04b0c36238ebf57e7@git.kernel.org>
Date:	Sun, 11 Oct 2015 13:15:52 -0700
From:	tip-bot for Rasmus Villemoes <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux@...musvillemoes.dk, mingo@...nel.org, hpa@...or.com,
	john.stultz@...aro.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de
Subject: [tip:timers/core] timers: Use __fls in apply_slack()

Commit-ID:  9fc4468d546b6eb55b0aa5b04b0c36238ebf57e7
Gitweb:     http://git.kernel.org/tip/9fc4468d546b6eb55b0aa5b04b0c36238ebf57e7
Author:     Rasmus Villemoes <linux@...musvillemoes.dk>
AuthorDate: Fri, 2 Oct 2015 09:45:30 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Sun, 11 Oct 2015 22:13:46 +0200

timers: Use __fls 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 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@...musvillemoes.dk>
Cc: John Stultz <john.stultz@...aro.org>
Link: http://lkml.kernel.org/r/1443771931-6284-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 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 d3f5e92..74591ba 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -874,7 +874,7 @@ 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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