[PATCH 3.14 34/78] sched/deadline: Change sched_getparam() behaviour vs SCHED_DEADLINE

[Greg Kroah-Hartman]

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>

commit ce5f7f8200ca2504f6f290044393d73ca314965a upstream.

The way we read POSIX one should only call sched_getparam() when
sched_getscheduler() returns either SCHED_FIFO or SCHED_RR.

Given that we currently return sched_param::sched_priority=0 for all
others, extend the same behaviour to SCHED_DEADLINE.

Requested-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Dario Faggioli <raistlin@xxxxxxxx>
Cc: linux-man <linux-man@xxxxxxxxxxxxxxx>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@xxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20140512205034.GH13467@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/sched/core.c |    9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3735,7 +3735,7 @@ SYSCALL_DEFINE1(sched_getscheduler, pid_
  */
 SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
 {
-	struct sched_param lp;
+	struct sched_param lp = { .sched_priority = 0 };
 	struct task_struct *p;
 	int retval;
 
@@ -3752,11 +3752,8 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, p
 	if (retval)
 		goto out_unlock;
 
-	if (task_has_dl_policy(p)) {
-		retval = -EINVAL;
-		goto out_unlock;
-	}
-	lp.sched_priority = p->rt_priority;
+	if (task_has_rt_policy(p))
+		lp.sched_priority = p->rt_priority;
 	rcu_read_unlock();
 
 	/*


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