Hi Jan,

running the attached test case for the native skin, you will get an ugly
lock-up on probably all Xenomai versions. Granted, this code is a bit
synthetic. I originally thought I could trigger the bug also via
timeouts when waiting on mutexes, but this scenario is safe (the timeout
is cleared before being able to cause harm).

just in order to educate me as probably I might have got something
wrong at the first glance :)

if we take this one:

--- mutex.c     2006-02-27 15:34:58.000000000 +0100
+++ mutex-NEW.c 2006-05-10 11:55:25.000000000 +0200
@@ -391,7 +391,7 @@ int rt_mutex_lock (RT_MUTEX *mutex,
        err = -EIDRM; /* Mutex deleted while pending. */
    else if (xnthread_test_flags(&task->thread_base,XNTIMEO))
        err = -ETIMEDOUT; /* Timeout.*/
-    else if (xnthread_test_flags(&task->thread_base,XNBREAK))
+    else if (xnthread_test_flags(&task->thread_base,XNBREAK) &&
mutex->owner != task)
        err = -EINTR; /* Unblocked.*/


As I understand task2 has a lower prio and that's why

[task1] rt_mutex_unlock
[task 1] rt_task_unblock(task1)

are called in a row.

ok, task2 wakes up in rt_mutex_unlock() (when task1 is blocked on
rt_mutex_lock()) and finds XNBREAK flag but,

[doc] -EINTR is returned if rt_task_unblock() has been called for the
waiting task (1) before the mutex has become available (2).

(1) it's true, task2 was still waiting at that time;
(2) it's wrong, task2 was already the owner.

So why just not to bail out XNBREAK and continue task2 as it has a
mutex (as shown above) ?

Best regards,
Dmitry Adamushko

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