[PATCH 3.8 46/65] sched/deadline: Change sched_getparam() behaviour vs SCHED_DEADLINE

[Kamal Mostafa]

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

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

From: Peter Zijlstra <peterz at infradead.org>

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 at gmail.com>
Signed-off-by: Peter Zijlstra <peterz at infradead.org>
Acked-by: Michael Kerrisk <mtk.manpages at gmail.com>
Cc: Dario Faggioli <raistlin at linux.it>
Cc: linux-man <linux-man at vger.kernel.org>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages at gmail.com>
Cc: Juri Lelli <juri.lelli at gmail.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Link: http://lkml.kernel.org/r/20140512205034.GH13467@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo at kernel.org>
[ kamal: backport to 3.8-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 kernel/sched/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5e2f7c3..8188769 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4039,7 +4039,7 @@ SYSCALL_DEFINE1(sched_getscheduler, pid_t, 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;
 
@@ -4056,7 +4056,8 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
 	if (retval)
 		goto out_unlock;
 
-	lp.sched_priority = p->rt_priority;
+	if (task_has_rt_policy(p))
+		lp.sched_priority = p->rt_priority;
 	rcu_read_unlock();
 
 	/*
-- 
1.9.1