Re: [Xenomai-help] pthread_mutex_lock returns 1

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Landau, Bracha wrote:
> Thanks for your help.
> 
> I tried to put in "printk"s in the kernel implementation of the
> xenomai pthread_mutex_lock, and it did not work. Neither did
> xnprintf. I did this in order to find out what is the exact cause of
> the error; generally adding printk's in the kernel implementation of
> functions did work, but on this one it didn't.
> 
> Is there any way to discern what exactly the problem is? This code
> was working on earlier versions of Xenomai (2.2) and did not generate
> an error on this instance of calling pthread_mutex_lock.

Either your mutex is not process-shared and you try to use it from a
different process (if that is the case, that is easy to know, you did
not call pthread_mutexattr_setpshared, and you try to access the mutex
from a different process, because you called fork after
pthread_mutex_init for instance, see
http://www.xenomai.org/index.php/Porting_POSIX_applications_to_Xenomai#Mixing_fork_with_Xenomai_POSIX_skin_services.
)

Or you are trying to lock the mutex from a thread which is not a Xenomai
thread (that is, a thread created with __real_pthread_create, or in some
part of the code where pthread_create is not wrapped with Xenomai POSIX
skin's compilation flags).

You do not tell us with what version of Xenomai you have the problem. If
this is 2.5-rc2, it is normal that you do not see your printks: the
mutexes fast path is now handled in user-space (so, now that you mention
it, I wonder if the pshared attribute works, so, you may have
pthread_mutex_lock which does not fail when it is handled in user-space,
and which fails when it has to go through kernel-space).


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-- 
                                          Gilles