[Xenomai-core] [RFC][PATCH 1/2] rework shadow CPU affinity

[Xenomai-core] [RFC][PATCH 1/2] rework shadow CPU affinity

[Jan Kiszka]

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Picking up the earlier discussion of CPU affinity of shadow threads,
this patch now opens the possibility to assign a CPU mask on
xnshadow_map. It cleans up the related nucleus code and updates all
callers of xnshadow_map appropriately.

Be warned, it's only tested on (q)emulated SMP. Comments and test
reports on real hardware are welcome.

Jan


PS: I would consider these patches for 2.4.

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---
 include/asm-generic/system.h |    1 -
 include/nucleus/pod.h        |    3 +++
 include/nucleus/shadow.h     |    4 +++-
 ksrc/nucleus/shadow.c        |   43 ++++++++++++++++++-------------------------
 ksrc/skins/native/syscall.c  |    3 ++-
 ksrc/skins/posix/syscall.c   |    4 ++--
 ksrc/skins/psos+/syscall.c   |    3 ++-
 ksrc/skins/vrtx/syscall.c    |    3 ++-
 ksrc/skins/vxworks/syscall.c |    3 ++-
 9 files changed, 34 insertions(+), 33 deletions(-)

Index: xenomai/include/asm-generic/system.h
===================================================================
--- xenomai.orig/include/asm-generic/system.h
+++ xenomai/include/asm-generic/system.h
@@ -38,7 +38,6 @@
 #include <asm/ptrace.h>
 #include <asm/xenomai/hal.h>
 #include <asm/xenomai/atomic.h>
-#include <nucleus/shadow.h>
 
 /* Tracer interface */
 #define xnarch_trace_max_begin(v)		rthal_trace_max_begin(v)
Index: xenomai/include/nucleus/shadow.h
===================================================================
--- xenomai.orig/include/nucleus/shadow.h
+++ xenomai/include/nucleus/shadow.h
@@ -22,6 +22,7 @@
 
 #include <asm/xenomai/atomic.h>
 #include <asm/xenomai/syscall.h>
+#include <asm/xenomai/system.h>
 #ifdef CONFIG_PROC_FS
 #include <linux/proc_fs.h>
 #endif /* CONFIG_PROC_FS */
@@ -65,7 +66,8 @@ void xnshadow_grab_events(void);
 void xnshadow_release_events(void);
 
 int xnshadow_map(struct xnthread *thread,
-		 xncompletion_t __user *u_completion);
+		 xncompletion_t __user *u_completion,
+		 xnarch_cpumask_t affinity);
 
 void xnshadow_unmap(struct xnthread *thread);
 
Index: xenomai/ksrc/nucleus/shadow.c
===================================================================
--- xenomai.orig/ksrc/nucleus/shadow.c
+++ xenomai/ksrc/nucleus/shadow.c
@@ -409,18 +409,6 @@ static void lostage_handler(void *cookie
 		xnltt_log_event(xeno_ev_lohandler, reqnum, p->comm, p->pid);
 
 		switch (rq->req[reqnum].type) {
-		case LO_START_REQ:
-
-#ifdef CONFIG_SMP
-			if (xnshadow_thread(p))
-				/* Set up the initial task affinity using the
-				   information passed to xnpod_start_thread(). */
-				set_cpus_allowed(p,
-						 xnshadow_thread(p)->affinity);
-#endif /* CONFIG_SMP */
-
-			goto do_wakeup;
-
 		case LO_WAKEUP_REQ:
 
 #ifdef CONFIG_SMP
@@ -443,7 +431,9 @@ static void lostage_handler(void *cookie
 			if (!xnshadow_thread(current))
 				xnpod_renice_root(XNPOD_ROOT_PRIO_BASE);
 #endif /* CONFIG_XENO_OPT_RPIDISABLE */
-		      do_wakeup:
+
+			/* fall through */
+		case LO_START_REQ:
 
 #ifdef CONFIG_XENO_OPT_ISHIELD
 			if (xnshadow_thread(p) &&
@@ -752,7 +742,8 @@ void xnshadow_exit(void)
 }
 
 /*!
- * \fn int xnshadow_map(xnthread_t *thread, xncompletion_t __user *u_completion)
+ * \fn int xnshadow_map(xnthread_t *thread, xncompletion_t __user *u_completion,
+ *                      xnarch_cpumask_t affinity)
  * @internal
  * \brief Create a shadow thread context.
  *
@@ -781,6 +772,9 @@ void xnshadow_exit(void)
  * immediately started and "current" immediately resumes in the Xenomai
  * domain from this service.
  *
+ * @param affinity The processor affinity of this thread. Passing
+ * XNPOD_ALL_CPUS or an empty affinity set means "any cpu".
+ *
  * @return 0 is returned on success. Otherwise:
  *
  * - -ERESTARTSYS is returned if the current Linux task has received a
@@ -803,9 +797,9 @@ void xnshadow_exit(void)
  *
  */
 
-int xnshadow_map(xnthread_t *thread, xncompletion_t __user * u_completion)
+int xnshadow_map(xnthread_t *thread, xncompletion_t __user * u_completion,
+		 xnarch_cpumask_t affinity)
 {
-	xnarch_cpumask_t affinity;
 	unsigned muxid, magic;
 	int mode, prio, err;
 
@@ -853,22 +847,21 @@ int xnshadow_map(xnthread_t *thread, xnc
 	xnshadow_thrptd(current) = thread;
 	xnpod_suspend_thread(thread, XNRELAX, XN_INFINITE, NULL);
 
+	/* Apply provided cpumask on the Linux task. */
+	set_cpus_allowed(current, affinity);
+
 	if (u_completion) {
 		xnshadow_signal_completion(u_completion, 0);
 		return 0;
 	}
 
-	/* Nobody waits for us, so we may start the shadow immediately
-	   after having forced the CPU affinity to the current
-	   processor. Note that we don't use smp_processor_id() to prevent
-	   kernel debug stuff to yell at us for calling it in a preemptible
-	   section of code. */
-
-	affinity = xnarch_cpumask_of_cpu(rthal_processor_id());
-	set_cpus_allowed(current, affinity);
+	/* Nobody waits for us, so we may start the shadow immediately. */
 
 	mode = thread->rrperiod != XN_INFINITE ? XNRRB : 0;
-	xnpod_start_thread(thread, mode, 0, affinity, NULL, NULL);
+	err = xnpod_start_thread(thread, mode, 0, affinity, NULL, NULL);
+
+	if (err)
+		return err;
 
 	err = xnshadow_harden();
 
Index: xenomai/include/nucleus/pod.h
===================================================================
--- xenomai.orig/include/nucleus/pod.h
+++ xenomai/include/nucleus/pod.h
@@ -33,6 +33,9 @@
 
 #include <nucleus/thread.h>
 #include <nucleus/intr.h>
+#if defined(__KERNEL__) && defined(CONFIG_XENO_OPT_PERVASIVE)
+#include <nucleus/shadow.h>
+#endif /* __KERNEL__  && CONFIG_XENO_OPT_PERVASIVE */
 
 /* Creation flags */
 #define XNREUSE  0x00000001     /* Reuse pod with identical properties */
Index: xenomai/ksrc/skins/native/syscall.c
===================================================================
--- xenomai.orig/ksrc/skins/native/syscall.c
+++ xenomai/ksrc/skins/native/syscall.c
@@ -173,7 +173,8 @@ static int __rt_task_create(struct task_
 		ph.opaque2 = bulk.a5;	/* hidden pthread_t identifier. */
 		__xn_copy_to_user(curr, (void __user *)bulk.a1, &ph,
 				  sizeof(ph));
-		err = xnshadow_map(&task->thread_base, u_completion);
+		err = xnshadow_map(&task->thread_base, u_completion,
+				   task->affinity);
 	} else {
 		xnfree(task);
 		/* Unblock and pass back error code. */
Index: xenomai/ksrc/skins/posix/syscall.c
===================================================================
--- xenomai.orig/ksrc/skins/posix/syscall.c
+++ xenomai/ksrc/skins/posix/syscall.c
@@ -174,7 +174,7 @@ static int __pthread_create(struct task_
 	if (err)
 		return -err;	/* Conventionally, our error codes are negative. */
 
-	err = xnshadow_map(&k_tid->threadbase, NULL);
+	err = xnshadow_map(&k_tid->threadbase, NULL, XNPOD_ALL_CPUS);
 
 	if (!err && !__pthread_hash(&hkey, k_tid))
 		err = -ENOMEM;
@@ -205,7 +205,7 @@ static pthread_t __pthread_shadow(struct
 	if (err)
 		return ERR_PTR(-err);
 
-	err = xnshadow_map(&k_tid->threadbase, NULL);
+	err = xnshadow_map(&k_tid->threadbase, NULL, XNPOD_ALL_CPUS);
 
 	if (!err && !__pthread_hash(hkey, k_tid))
 		err = -EAGAIN;
Index: xenomai/ksrc/skins/psos+/syscall.c
===================================================================
--- xenomai.orig/ksrc/skins/psos+/syscall.c
+++ xenomai/ksrc/skins/psos+/syscall.c
@@ -98,7 +98,8 @@ static int __t_create(struct task_struct
 		tid = xnthread_handle(&task->threadbase);
 		__xn_copy_to_user(curr, (void __user *)__xn_reg_arg4(regs), &tid,
 				  sizeof(tid));
-		err = xnshadow_map(&task->threadbase, u_completion);
+		err = xnshadow_map(&task->threadbase, u_completion,
+				   XNPOD_ALL_CPUS);
 	} else {
 		/* Unblock and pass back error code. */
 
Index: xenomai/ksrc/skins/vrtx/syscall.c
===================================================================
--- xenomai.orig/ksrc/skins/vrtx/syscall.c
+++ xenomai/ksrc/skins/vrtx/syscall.c
@@ -95,7 +95,8 @@ static int __sc_tecreate(struct task_str
 	} else {
 		__xn_copy_to_user(curr, (void __user *)__xn_reg_arg2(regs),
 				  &tid, sizeof(tid));
-		err = xnshadow_map(&task->threadbase, u_completion);
+		err = xnshadow_map(&task->threadbase, u_completion,
+				   XNPOD_ALL_CPUS);
 	}
 
 	if (err)
Index: xenomai/ksrc/skins/vxworks/syscall.c
===================================================================
--- xenomai.orig/ksrc/skins/vxworks/syscall.c
+++ xenomai/ksrc/skins/vxworks/syscall.c
@@ -122,7 +122,8 @@ static int __wind_task_init(struct task_
 		ph.handle = xnthread_handle(&task->threadbase);
 		__xn_copy_to_user(curr, (void __user *)__xn_reg_arg2(regs), &ph,
 				  sizeof(ph));
-		err = xnshadow_map(&task->threadbase, u_completion);
+		err = xnshadow_map(&task->threadbase, u_completion,
+				   XNPOD_ALL_CPUS);
 	} else {
 		/* Unblock and pass back error code. */
 

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[Xenomai-core] Re: [RFC][PATCH 1/2] rework shadow CPU affinity

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> Picking up the earlier discussion of CPU affinity of shadow threads,
> this patch now opens the possibility to assign a CPU mask on
> xnshadow_map. It cleans up the related nucleus code and updates all
> callers of xnshadow_map appropriately.
> 
> Be warned, it's only tested on (q)emulated SMP. Comments and test
> reports on real hardware are welcome.

It is only possible to set the affinity of a user-space thread, why
adding another way to do it ?

-- 
                                                 Gilles Chanteperdrix

Re: [Xenomai-core] Re: [RFC][PATCH 1/2] rework shadow CPU affinity

[Jan Kiszka]

Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Picking up the earlier discussion of CPU affinity of shadow threads,
>> this patch now opens the possibility to assign a CPU mask on
>> xnshadow_map. It cleans up the related nucleus code and updates all
>> callers of xnshadow_map appropriately.
>>
>> Be warned, it's only tested on (q)emulated SMP. Comments and test
>> reports on real hardware are welcome.
> 
> It is only possible to set the affinity of a user-space thread, why
> adding another way to do it ?
> 

I'm not yet completely understanding what you mean.

So far the affinity was indirectly assigned to some xnthread by the CPU
the caller of xnshadow_map happened to run on. Now this is done
explicitly, thus in a more robust way (there was an undefined path in
the old code) and without duplicating code (/wrt skins).

Jan

Re: [Xenomai-core] Re: [RFC][PATCH 1/2] rework shadow CPU affinity

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
> 
>>Jan Kiszka wrote:
>>
>>>Picking up the earlier discussion of CPU affinity of shadow threads,
>>>this patch now opens the possibility to assign a CPU mask on
>>>xnshadow_map. It cleans up the related nucleus code and updates all
>>>callers of xnshadow_map appropriately.
>>>
>>>Be warned, it's only tested on (q)emulated SMP. Comments and test
>>>reports on real hardware are welcome.
>>
>>It is only possible to set the affinity of a user-space thread, why
>>adding another way to do it ?
>>
> 
> 
> I'm not yet completely understanding what you mean.
> 
> So far the affinity was indirectly assigned to some xnthread by the CPU
> the caller of xnshadow_map happened to run on. Now this is done
> explicitly, thus in a more robust way (there was an undefined path in
> the old code) and without duplicating code (/wrt skins).

I meant "already" instead of "only", it is already possible to set the
affinity of a user-space thread with sched_setaffinity.

-- 
                                                 Gilles Chanteperdrix

Re: [Xenomai-core] Re: [RFC][PATCH 1/2] rework shadow CPU affinity

[Jan Kiszka]

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Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> Gilles Chanteperdrix wrote:
>>
>>> Jan Kiszka wrote:
>>>
>>>> Picking up the earlier discussion of CPU affinity of shadow threads,
>>>> this patch now opens the possibility to assign a CPU mask on
>>>> xnshadow_map. It cleans up the related nucleus code and updates all
>>>> callers of xnshadow_map appropriately.
>>>>
>>>> Be warned, it's only tested on (q)emulated SMP. Comments and test
>>>> reports on real hardware are welcome.
>>> It is only possible to set the affinity of a user-space thread, why
>>> adding another way to do it ?
>>>
>>
>> I'm not yet completely understanding what you mean.
>>
>> So far the affinity was indirectly assigned to some xnthread by the CPU
>> the caller of xnshadow_map happened to run on. Now this is done
>> explicitly, thus in a more robust way (there was an undefined path in
>> the old code) and without duplicating code (/wrt skins).
> 
> I meant "already" instead of "only", it is already possible to set the
> affinity of a user-space thread with sched_setaffinity.
> 

OK. So you are suggesting to read out the affinity mask from task_struct
instead of passing it as an additional argument?


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Re: [Xenomai-core] Re: [RFC][PATCH 1/2] rework shadow CPU affinity

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> OK. So you are suggesting to read out the affinity mask from task_struct
> instead of passing it as an additional argument?
> 

Unless I am wrong, it is the way it currently works.

-- 
                                                 Gilles Chanteperdrix

Re: [Xenomai-core] Re: [RFC][PATCH 1/2] rework shadow CPU affinity

[Jan Kiszka]

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Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
>> OK. So you are suggesting to read out the affinity mask from task_struct
>> instead of passing it as an additional argument?
>>
> 
> Unless I am wrong, it is the way it currently works.
> 

Yes, for the posix skin. But native is different due to the spilt-up
create/start and its own affinity API. And that caused problems when
applying nkaffinity.

Nevertheless, I should try to combine the cleanup of xnshadow_map with
passing the mask ALWAYS in task_struct. Let's see how this works out,
most likely with less patching.


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Re: [Xenomai-core] Re: [RFC][PATCH 1/2] rework shadow CPU affinity

[Jan Kiszka]

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Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> OK. So you are suggesting to read out the affinity mask from task_struct
>>> instead of passing it as an additional argument?
>>>
>> Unless I am wrong, it is the way it currently works.
>>
> 
> Yes, for the posix skin. But native is different due to the spilt-up
> create/start and its own affinity API. And that caused problems when
> applying nkaffinity.
> 
> Nevertheless, I should try to combine the cleanup of xnshadow_map with
> passing the mask ALWAYS in task_struct. Let's see how this works out,
> most likely with less patching.

sched_setaffinity is 2.6 only. So we would have to push the mask
application into kernel space for the native skin anyway. Hmm.

What are posix skin users supposed to do over 2.4? Upgrade to 2.6? BTW,
do you plan to support pthread_attr_setaffinity_np somehow?

Jan


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Re: [Xenomai-core] Re: [RFC][PATCH 1/2] rework shadow CPU affinity

[Gilles Chanteperdrix]

Jan Kiszka wrote:
> Jan Kiszka wrote:
> 
>>Gilles Chanteperdrix wrote:
>>
>>>Jan Kiszka wrote:
>>>
>>>>OK. So you are suggesting to read out the affinity mask from task_struct
>>>>instead of passing it as an additional argument?
>>>>
>>>
>>>Unless I am wrong, it is the way it currently works.
>>>
>>
>>Yes, for the posix skin. But native is different due to the spilt-up
>>create/start and its own affinity API. And that caused problems when
>>applying nkaffinity.
>>
>>Nevertheless, I should try to combine the cleanup of xnshadow_map with
>>passing the mask ALWAYS in task_struct. Let's see how this works out,
>>most likely with less patching.
> 
> 
> sched_setaffinity is 2.6 only. So we would have to push the mask
> application into kernel space for the native skin anyway. Hmm.
> 
> What are posix skin users supposed to do over 2.4?


Right, I did not think about the 2.4 kernel, but I am not sure there are
many people using the 2.4 kernel on SMP machines anyway.

As for the native skin, it already allows to pass the affinity to
rt_task_create, using T_CPU.


> Upgrade to 2.6? BTW, do you plan to support pthread_attr_setaffinity_np somehow?

pthread_attr_setaffinity_np is implemented in kernel space, and the
pthread_attr_t is passed unchanged by __wrap_pthread_create to
__real_pthread_create. So pthread_attr_setaffinity_np should be already
working provided that you use a libc that supports it.

> 
> Jan
> 


-- 
                                                 Gilles Chanteperdrix

Re: [Xenomai-core] Re: [RFC][PATCH 1/2] rework shadow CPU affinity

[Philippe Gerum]

On Wed, 2006-11-29 at 11:54 +0100, Gilles Chanteperdrix wrote:
> Jan Kiszka wrote:
> > Jan Kiszka wrote:
> > 
> >>Gilles Chanteperdrix wrote:
> >>
> >>>Jan Kiszka wrote:
> >>>
> >>>>OK. So you are suggesting to read out the affinity mask from task_struct
> >>>>instead of passing it as an additional argument?
> >>>>
> >>>
> >>>Unless I am wrong, it is the way it currently works.
> >>>
> >>
> >>Yes, for the posix skin. But native is different due to the spilt-up
> >>create/start and its own affinity API. And that caused problems when
> >>applying nkaffinity.
> >>
> >>Nevertheless, I should try to combine the cleanup of xnshadow_map with
> >>passing the mask ALWAYS in task_struct. Let's see how this works out,
> >>most likely with less patching.
> > 
> > 
> > sched_setaffinity is 2.6 only. So we would have to push the mask
> > application into kernel space for the native skin anyway. Hmm.
> > 
> > What are posix skin users supposed to do over 2.4?
> 
> 
> Right, I did not think about the 2.4 kernel, but I am not sure there are
> many people using the 2.4 kernel on SMP machines anyway.

Ack. 2.4 backports are provided to help people who do not want to double
jump from <some-rtos> to Xenomai _and_ from 2.4 to 2.6 in the same move
for upgrading some embedded setup; they can move to Xenomai keeping
their good old system software if they wish, then move to 2.6 if they
wish so later, once the dust has settled. People interested by
multi-cores and/or big irons of some sort should obviously go for 2.6.

> 
> As for the native skin, it already allows to pass the affinity to
> rt_task_create, using T_CPU.
> 
> 
> > Upgrade to 2.6? BTW, do you plan to support pthread_attr_setaffinity_np somehow?
> 
> pthread_attr_setaffinity_np is implemented in kernel space, and the
> pthread_attr_t is passed unchanged by __wrap_pthread_create to
> __real_pthread_create. So pthread_attr_setaffinity_np should be already
> working provided that you use a libc that supports it.
> 
> > 
> > Jan
> > 
> 
> 
-- 
Philippe.

Re: [Xenomai-core] [RFC][PATCH 1/2] rework shadow CPU affinity

[Jan Kiszka]

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Second try of this patch, now consequently basing the affinity API for
xnshadow_map on current->cpus_allowed (affects the native skin). Just
like the current code does, this patch restricts a shadow thread to a
single (the first) CPU of its affinity mask.

Jan

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---
 ksrc/nucleus/shadow.c       |   35 +++++++++++++----------------------
 ksrc/skins/native/syscall.c |    3 +++
 2 files changed, 16 insertions(+), 22 deletions(-)

Index: xenomai/ksrc/nucleus/shadow.c
===================================================================
--- xenomai.orig/ksrc/nucleus/shadow.c
+++ xenomai/ksrc/nucleus/shadow.c
@@ -409,18 +409,6 @@ static void lostage_handler(void *cookie
 		xnltt_log_event(xeno_ev_lohandler, reqnum, p->comm, p->pid);
 
 		switch (rq->req[reqnum].type) {
-		case LO_START_REQ:
-
-#ifdef CONFIG_SMP
-			if (xnshadow_thread(p))
-				/* Set up the initial task affinity using the
-				   information passed to xnpod_start_thread(). */
-				set_cpus_allowed(p,
-						 xnshadow_thread(p)->affinity);
-#endif /* CONFIG_SMP */
-
-			goto do_wakeup;
-
 		case LO_WAKEUP_REQ:
 
 #ifdef CONFIG_SMP
@@ -443,7 +431,9 @@ static void lostage_handler(void *cookie
 			if (!xnshadow_thread(current))
 				xnpod_renice_root(XNPOD_ROOT_PRIO_BASE);
 #endif /* CONFIG_XENO_OPT_RPIDISABLE */
-		      do_wakeup:
+
+			/* fall through */
+		case LO_START_REQ:
 
 #ifdef CONFIG_XENO_OPT_ISHIELD
 			if (xnshadow_thread(p) &&
@@ -853,22 +843,23 @@ int xnshadow_map(xnthread_t *thread, xnc
 	xnshadow_thrptd(current) = thread;
 	xnpod_suspend_thread(thread, XNRELAX, XN_INFINITE, NULL);
 
+	/* Restrict affinity to a single CPU of the current set */
+	affinity = xnarch_cpumask_of_cpu(
+		xnarch_first_cpu(current->cpus_allowed));
+	set_cpus_allowed(current, affinity);
+
 	if (u_completion) {
 		xnshadow_signal_completion(u_completion, 0);
 		return 0;
 	}
 
-	/* Nobody waits for us, so we may start the shadow immediately
-	   after having forced the CPU affinity to the current
-	   processor. Note that we don't use smp_processor_id() to prevent
-	   kernel debug stuff to yell at us for calling it in a preemptible
-	   section of code. */
-
-	affinity = xnarch_cpumask_of_cpu(rthal_processor_id());
-	set_cpus_allowed(current, affinity);
+	/* Nobody waits for us, so we may start the shadow immediately. */
 
 	mode = thread->rrperiod != XN_INFINITE ? XNRRB : 0;
-	xnpod_start_thread(thread, mode, 0, affinity, NULL, NULL);
+	err = xnpod_start_thread(thread, mode, 0, affinity, NULL, NULL);
+
+	if (err)
+		return err;
 
 	err = xnshadow_harden();
 
Index: xenomai/ksrc/skins/native/syscall.c
===================================================================
--- xenomai.orig/ksrc/skins/native/syscall.c
+++ xenomai/ksrc/skins/native/syscall.c
@@ -168,6 +168,9 @@ static int __rt_task_create(struct task_
 	err = rt_task_create(task, name, 0, prio, XNFPU | XNSHADOW | mode);
 
 	if (err == 0) {
+		/* Apply CPU affinity */
+		set_cpus_allowed(current, task->affinity);
+
 		/* Copy back the registry handle to the ph struct. */
 		ph.opaque = xnthread_handle(&task->thread_base);
 		ph.opaque2 = bulk.a5;	/* hidden pthread_t identifier. */

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