sched: rt-group: fixup schedulability constraints calculation

it was only possible to configure the rt-group scheduling parameters
beyond the default value in a very small range.

that's because div64_64() has a different calling convention than
do_div() :/

fix a few untidies while we are 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@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 5b13e4b..b8ee864 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7726,9 +7726,7 @@ static unsigned long to_ratio(u64 period, u64 runtime)
        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)
@@ -7757,18 +7755,16 @@ int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
        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);