linux-kernel - [PATCH] sched: rt-group: fixup schedulability constraints calculation

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Date:	Wed, 27 Feb 2008 12:00:46 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] sched: rt-group: fixup schedulability constraints
	calculation

Subject: sched: rt-group: fixup schedulability constraints calculation

div64_64() has a different calling convention than do_div() :/

fix a few untidies while were here; sysctl_sched_rt_period may overflow
due to that multiplication, so cast to u64 first. Also that RUNTIME_INF
juggling makes little sense although its an effective NOP.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 kernel/sched.c |   10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -7934,9 +7934,7 @@ static unsigned long to_ratio(u64 period
 	if (runtime == RUNTIME_INF)
 		return 1ULL << 16;
 
-	runtime *= (1ULL << 16);
-	div64_64(runtime, period);
-	return runtime;
+	return div64_64(runtime << 16, period);
 }
 
 static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
@@ -7965,18 +7963,16 @@ int sched_group_set_rt_runtime(struct ta
 	u64 rt_runtime, rt_period;
 	int err = 0;
 
-	rt_period = sysctl_sched_rt_period * NSEC_PER_USEC;
+	rt_period = (u64)sysctl_sched_rt_period * NSEC_PER_USEC;
 	rt_runtime = (u64)rt_runtime_us * NSEC_PER_USEC;
 	if (rt_runtime_us == -1)
-		rt_runtime = rt_period;
+		rt_runtime = RUNTIME_INF;
 
 	mutex_lock(&rt_constraints_mutex);
 	if (!__rt_schedulable(tg, rt_period, rt_runtime)) {
 		err = -EINVAL;
 		goto unlock;
 	}
-	if (rt_runtime_us == -1)
-		rt_runtime = RUNTIME_INF;
 	tg->rt_runtime = rt_runtime;
  unlock:
 	mutex_unlock(&rt_constraints_mutex);


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