sched: reintroduce the sched_min_granularity tunable

we lost the sched_min_granularity tunable to a clever optimization
that uses the sched_latency/min_granularity ratio - but the ratio
is quite unintuitive to users and can also crash the kernel if the
ratio is set to 0. So reintroduce the min_granularity tunable,
while keeping the ratio maintained internally.

no functionality changed.

[ mingo@elte.hu: some fixlets. ]

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 3b4efbe..6e3b63c 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -235,11 +235,14 @@
 #ifdef CONFIG_SCHED_DEBUG
 	{
 		.ctl_name	= CTL_UNNUMBERED,
-		.procname	= "sched_nr_latency",
-		.data		= &sysctl_sched_nr_latency,
+		.procname	= "sched_min_granularity_ns",
+		.data		= &sysctl_sched_min_granularity,
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
-		.proc_handler	= &proc_dointvec,
+		.proc_handler	= &sched_nr_latency_handler,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &min_sched_granularity_ns,
+		.extra2		= &max_sched_granularity_ns,
 	},
 	{
 		.ctl_name	= CTL_UNNUMBERED,
@@ -247,7 +250,7 @@
 		.data		= &sysctl_sched_latency,
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
-		.proc_handler	= &proc_dointvec_minmax,
+		.proc_handler	= &sched_nr_latency_handler,
 		.strategy	= &sysctl_intvec,
 		.extra1		= &min_sched_granularity_ns,
 		.extra2		= &max_sched_granularity_ns,