Hi all,

I'm having trouble trying to share a semaphore that is created in
user-space context with a rtdm-driver that runs in kernel-space. I was
hoping you could explain me what I'm doing wrong.

I'm using a posix-skin based user-space Xenomai application that runs
a loop which is triggered by a semaphore.
This semaphore is posted by a pthread that runs at a specific
frequency. However, I want to be able to synchronize this loop with an
external hardware trigger that is read out by a rtdm-driver. To do so,
I try to disable the semaphore-post in the user-mode pthread, and
re-use the existing semaphore in kernel-mode (the rtdm-driver).
Unfortunately, the rtdm-driver is not able to find the user-space
created semaphore.

I wrote a little test-program to explain the problem. If required, I
will post the complete test-program, but for now I will show some

In the user-space application a semphore is created using the sem_open sys-call:

  clockSem = sem_open(SEMNAME, O_CREAT, 0, 0);

clockSem, which is a pointer to sem_t returns an address (!= SEM_FAILED).
With an ioctl-call I try to open the same semaphore in kernel-mode:

  sem_p = sem_open(SEMNAME, 0);

This fails. sem_p equals SEM_FAILED, and errno is set to 2 (ENOENT).

I'm runing Linux x86 32bit, Xenomai 2.4.8, ipipe 2.4-01


Remco den Breeje

Xenomai-core mailing list

Reply via email to