linux-kernel - [tip:timers/core] hrtimer: Update active_bases before calling hrtimer_force

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Date:	Wed, 22 Apr 2015 12:04:47 -0700
From:	tip-bot for Viresh Kumar <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	hpa@...or.com, peterz@...radead.org, fweisbec@...il.com,
	preeti@...ux.vnet.ibm.com, tglx@...utronix.de,
	viresh.kumar@...aro.org, mtosatti@...hat.com,
	linux-kernel@...r.kernel.org, mingo@...nel.org
Subject: [tip:timers/core] hrtimer:
  Update active_bases before calling hrtimer_force_reprogram()

Commit-ID:  d9f0acdeef48570c4e6159d3108f12b64571392e
Gitweb:     http://git.kernel.org/tip/d9f0acdeef48570c4e6159d3108f12b64571392e
Author:     Viresh Kumar <viresh.kumar@...aro.org>
AuthorDate: Tue, 14 Apr 2015 21:08:25 +0000
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Wed, 22 Apr 2015 17:06:48 +0200

hrtimer: Update active_bases before calling hrtimer_force_reprogram()

'active_bases' indicates which clock-base have active timer. The
intention of this bit field was to avoid evaluating inactive bases. It
was introduced with the introduction of the BOOTTIME and TAI clock
bases, but it was never brought into full use.

We want to use it now, but in __remove_hrtimer() the update happens
after the calling hrtimer_force_reprogram() which has to evaluate all
clock bases for the next expiring timer. So in case the last timer of
a clock base got removed we still see the active bit and therefor
evaluate the clock base for no value. There are further optimizations
possible when active_bases is updated in the right place.

Move the update before the call to hrtimer_force_reprogram()

[ tglx: Massaged changelog ]

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
Reviewed-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@...radead.org>
Cc: Marcelo Tosatti <mtosatti@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: linaro-kernel@...ts.linaro.org
Link: http://lkml.kernel.org/r/20150414203500.533438642@linutronix.de
Link: http://lkml.kernel.org/r/c7c8ebcd9ed88bb09d76059c745a1fafb48314e7.1428039899.git.viresh.kumar@linaro.org
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/time/hrtimer.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index b1a74ee..9abd50b 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -887,6 +887,9 @@ static void __remove_hrtimer(struct hrtimer *timer,
 
 	next_timer = timerqueue_getnext(&base->active);
 	timerqueue_del(&base->active, &timer->node);
+	if (!timerqueue_getnext(&base->active))
+		base->cpu_base->active_bases &= ~(1 << base->index);
+
 	if (&timer->node == next_timer) {
 #ifdef CONFIG_HIGH_RES_TIMERS
 		/* Reprogram the clock event device. if enabled */
@@ -900,8 +903,6 @@ static void __remove_hrtimer(struct hrtimer *timer,
 		}
 #endif
 	}
-	if (!timerqueue_getnext(&base->active))
-		base->cpu_base->active_bases &= ~(1 << base->index);
 out:
 	timer->state = newstate;
 }
--
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