sched/deadline: Change sched_getparam() behaviour vs SCHED_DEADLINE

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@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Dario Faggioli <raistlin@linux.it>
Cc: linux-man <linux-man@vger.kernel.org>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140512205034.GH13467@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 55dc803..9fd076a 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3735,7 +3735,7 @@ 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;
 
@@ -3752,11 +3752,8 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
        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();
 
        /*