sched: allow cpuacct stats to be reset

Currently the schedstats implementation does not allow the statistics
to be reset. This patch aims to allow that.

  echo 0 > cpuacct.usage

resets the usage. Any other value is not allowed and returns -EINVAL.

Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index e2f85c7a7476291fb2f3228ecf13897dad359449..e4bf4477aee5e823837a8fb234b19df18df1dc8b 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8381,10 +8381,34 @@ static u64 cpuusage_read(struct cgroup *cgrp, struct cftype *cft)
        return totalcpuusage;
 }
 
+static int cpuusage_write(struct cgroup *cgrp, struct cftype *cftype,
+                                                               u64 reset)
+{
+       struct cpuacct *ca = cgroup_ca(cgrp);
+       int err = 0;
+       int i;
+
+       if (reset) {
+               err = -EINVAL;
+               goto out;
+       }
+
+       for_each_possible_cpu(i) {
+               u64 *cpuusage = percpu_ptr(ca->cpuusage, i);
+
+               spin_lock_irq(&cpu_rq(i)->lock);
+               *cpuusage = 0;
+               spin_unlock_irq(&cpu_rq(i)->lock);
+       }
+out:
+       return err;
+}
+
 static struct cftype files[] = {
        {
                .name = "usage",
                .read_uint = cpuusage_read,
+               .write_uint = cpuusage_write,
        },
 };