sched: Move SCHED_RESET_ON_FORK into attr::sched_flags

I noticed the new sched_{set,get}attr() calls didn't properly deal
with the SCHED_RESET_ON_FORK hack.

Instead of propagating the flags in high bits nonsense use the brand
spanking new attr::sched_flags field.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Dario Faggioli <raistlin@linux.it>
Link: http://lkml.kernel.org/r/20140115162242.GJ31570@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
index 2d5e49a..34f9d73 100644 (file)
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -40,8 +40,13 @@
 /* SCHED_ISO: reserved but not implemented yet */
 #define SCHED_IDLE             5
 #define SCHED_DEADLINE         6
+
 /* Can be ORed in to make sure the process is reverted back to SCHED_NORMAL on fork */
 #define SCHED_RESET_ON_FORK     0x40000000
 
+/*
+ * For the sched_{set,get}attr() calls
+ */
+#define SCHED_FLAG_RESET_ON_FORK       0x01
 
 #endif /* _UAPI_LINUX_SCHED_H */

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5a6ccdf..93a2836 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3267,8 +3267,7 @@ recheck:
                reset_on_fork = p->sched_reset_on_fork;
                policy = oldpolicy = p->policy;
        } else {
-               reset_on_fork = !!(policy & SCHED_RESET_ON_FORK);
-               policy &= ~SCHED_RESET_ON_FORK;
+               reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
 
                if (policy != SCHED_DEADLINE &&
                                policy != SCHED_FIFO && policy != SCHED_RR &&
@@ -3277,6 +3276,9 @@ recheck:
                        return -EINVAL;
        }
 
+       if (attr->sched_flags & ~(SCHED_FLAG_RESET_ON_FORK))
+               return -EINVAL;
+
        /*
         * Valid priorities for SCHED_FIFO and SCHED_RR are
         * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
@@ -3443,6 +3445,26 @@ change:
        return 0;
 }
 
+static int _sched_setscheduler(struct task_struct *p, int policy,
+                              const struct sched_param *param, bool check)
+{
+       struct sched_attr attr = {
+               .sched_policy   = policy,
+               .sched_priority = param->sched_priority,
+               .sched_nice     = PRIO_TO_NICE(p->static_prio),
+       };
+
+       /*
+        * Fixup the legacy SCHED_RESET_ON_FORK hack
+        */
+       if (policy & SCHED_RESET_ON_FORK) {
+               attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
+               policy &= ~SCHED_RESET_ON_FORK;
+               attr.sched_policy = policy;
+       }
+
+       return __sched_setscheduler(p, &attr, check);
+}
 /**
  * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
  * @p: the task in question.
@@ -3456,12 +3478,7 @@ change:
 int sched_setscheduler(struct task_struct *p, int policy,
                       const struct sched_param *param)
 {
-       struct sched_attr attr = {
-               .sched_policy   = policy,
-               .sched_priority = param->sched_priority,
-               .sched_nice     = PRIO_TO_NICE(p->static_prio),
-       };
-       return __sched_setscheduler(p, &attr, true);
+       return _sched_setscheduler(p, policy, param, true);
 }
 EXPORT_SYMBOL_GPL(sched_setscheduler);
 
@@ -3487,12 +3504,7 @@ EXPORT_SYMBOL_GPL(sched_setattr);
 int sched_setscheduler_nocheck(struct task_struct *p, int policy,
                               const struct sched_param *param)
 {
-       struct sched_attr attr = {
-               .sched_policy   = policy,
-               .sched_priority = param->sched_priority,
-               .sched_nice     = PRIO_TO_NICE(p->static_prio),
-       };
-       return __sched_setscheduler(p, &attr, false);
+       return _sched_setscheduler(p, policy, param, false);
 }
 
 static int
@@ -3792,6 +3804,8 @@ SYSCALL_DEFINE3(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
                goto out_unlock;
 
        attr.sched_policy = p->policy;
+       if (p->sched_reset_on_fork)
+               attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
        if (task_has_dl_policy(p))
                __getparam_dl(p, &attr);
        else if (task_has_rt_policy(p))