[Xenomai-core] [PATCH v2 1/4] POSIX: Fix SCHED_RR thread creation

[Jan Kiszka <jan.kiszka@domain.hid>]

SCHED_RR threads created via pthread_create do not receive the
round-robin property at kernel side. Fix this by pushing the policy as
an additional argument to __pse51_thread_create down to the kernel.
Moreover, enforce SCHED_FIFO for the Linux part of those threads.

Signed-off-by: Jan Kiszka <jan.kiszka@domain.hid>
---

 ksrc/skins/posix/syscall.c |    4 ++--
 src/skins/posix/thread.c   |   11 ++++++-----
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/ksrc/skins/posix/syscall.c b/ksrc/skins/posix/syscall.c
index 99c2a16..3480142 100644
--- a/ksrc/skins/posix/syscall.c
+++ b/ksrc/skins/posix/syscall.c
@@ -167,7 +167,7 @@ static int __pthread_create(struct pt_regs *regs)
 	   calling context. */
 
 	pthread_attr_init(&attr);
-	attr.policy = p->policy;
+	attr.policy = __xn_reg_arg2(regs);
 	attr.detachstate = PTHREAD_CREATE_DETACHED;
 	attr.schedparam_ex.sched_priority = p->rt_priority;
 	attr.fp = 1;
@@ -179,7 +179,7 @@ static int __pthread_create(struct pt_regs *regs)
 		return -err;	/* Conventionally, our error codes are negative. */
 
 	err = xnshadow_map(&k_tid->threadbase, NULL,
-			   (unsigned long __user *)__xn_reg_arg2(regs));
+			   (unsigned long __user *)__xn_reg_arg3(regs));
 
 	if (!err && !__pthread_hash(&hkey, k_tid))
 		err = -ENOMEM;
diff --git a/src/skins/posix/thread.c b/src/skins/posix/thread.c
index f32c7e1..4cf4e1c 100644
--- a/src/skins/posix/thread.c
+++ b/src/skins/posix/thread.c
@@ -192,6 +192,9 @@ static void *__pthread_trampoline(void *arg)
 
 	param.sched_priority = iargs->prio;
 	policy = iargs->policy;
+	if (policy == SCHED_RR)
+		/* Restrict round-robin scheduling to the Xenomai domain. */
+		policy = SCHED_FIFO;
 	parent_prio = iargs->parent_prio;
 	mode_buf = xeno_init_current_mode();
 
@@ -203,8 +206,8 @@ static void *__pthread_trampoline(void *arg)
 
 	/* Do _not_ inline the call to pthread_self() in the syscall
 	   macro: this trashes the syscall regs on some archs. */
-	err = XENOMAI_SKINCALL2(__pse51_muxid, __pse51_thread_create, tid,
-				mode_buf);
+	err = XENOMAI_SKINCALL3(__pse51_muxid, __pse51_thread_create, tid,
+				iargs->policy, mode_buf);
 	iargs->ret = -err;
 
 	/* We must save anything we'll need to use from *iargs on our own
@@ -221,9 +224,7 @@ static void *__pthread_trampoline(void *arg)
 	__real_sem_post(&iargs->sync);
 
 	if (!err) {
-		/* Broken pthread libs ignore some of the thread attribute specs
-		   passed to pthread_create(3), so we force the scheduling policy
-		   once again here. */
+		/* Adjust to final Linux policy and priority. */
 		__real_pthread_setschedparam(tid, policy, &param);
 
 		/* If the thread running pthread_create runs with the same