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>

1 files changed, 3 insertions, 7 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 5b13e4b0e009..b8ee864c7481 100644
--- 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);