My customer managed to find another hidden door to Xenomai's hell:
Trying to create a Xenomai POSIX thread from within a native thread. A
think the other way around would "work" as well. The precise scenario
was native thread -> dlopen(libs that's linked against libpthread_rt) ->
__init_posix_interface -> __wrap_pthread_setschedparam -> oops. That
scenario revealed two more issues in fact.

Here is a patch to remove this hell gate by catching xnshadow_map
invocations from withing already mapped shadow thread.

Jan

---
 ChangeLog             |    5 +++++
 ksrc/nucleus/shadow.c |    5 +++++
 2 files changed, 10 insertions(+)

Index: xenomai/ksrc/nucleus/shadow.c
===================================================================
--- xenomai.orig/ksrc/nucleus/shadow.c
+++ xenomai/ksrc/nucleus/shadow.c
@@ -1334,6 +1334,8 @@ void xnshadow_exit(void)
  * - -EINVAL is returned if the thread control block does not bear the
  * XNSHADOW bit, or if the thread has already been mapped.
  *
+ * - -EBUSY is returned if the current Linux task is already mapped.
+ *
  * Environments:
  *
  * This service can be called from:
@@ -1351,6 +1353,9 @@ int xnshadow_map(xnthread_t *thread, xnc
        unsigned muxid, magic;
        int err;

+       if (xnshadow_thread(current))
+               return -EBUSY;
+
        if (!xnthread_test_state(thread, XNSHADOW))
                return -EINVAL;

Index: xenomai/ChangeLog
===================================================================
--- xenomai.orig/ChangeLog
+++ xenomai/ChangeLog
@@ -1,3 +1,8 @@
+2008-11-21  Jan Kiszka  <[EMAIL PROTECTED]>
+
+       * ksrc/nucleus/shadow.c (xnshadow_map): Reject already mapped
+       tasks with -EBUSY.
+
 2008-11-16  Philippe Gerum  <[EMAIL PROTECTED]>

        * ksrc/arch/blackfin/patches: Upgrade to to
-- 
Siemens AG, Corporate Technology, CT SE 2 ES-OS
Corporate Competence Center Embedded Linux

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