Re: [Xenomai] xenomai-3.0-rc5 : binding named semaphores from external process

[Philippe Gerum <rpm@xenomai.org>]

On 07/29/2015 01:48 PM, Frederik Bayart wrote:
>> On Wednesday, 29 July 2015, 12:12, Philippe Gerum <rpm@xenomai.org> wrote:
>>
>>
>> On 07/28/2015 05:19 PM, Frederik Bayart wrote:
>>>>> ./stest --session=foo 1
>>>>>
>>>>> The first process binds to the named semaphore which is not yet created. According to the description of rt_sem_bind,  if the object does not exist on entry, the caller may block until a semaphore of the given name is created.
>>>>>
>>>>> So based on this description, I would I expect that if the second process is started, the first process would bind and continue and blocks in the p operation. The same for the 2nd process. Is this correct ? At the moment, if I start the 2nd process, I get a segfault in rt_sem_create :
>>>>>
>>>>> [ 9758.887921] [Xenomai] switching main to secondary mode after exception #14 from user-space at 0x7f6ad8c4a43e (pid 9256)
>>>>> [ 9758.887930] main[9256]: segfault at 7f903bf6e038 ip 00007f6ad8c4a43e sp 00007fffbd2c2eb8 error 6 in libcobalt.so.2.0.0[7f6ad8c3d000+1e000]
>>>>>
>>>>
>>>> Looking at the copperplate code, yep, this definitely can't work. Ok,
>>>> queued.
>>>
>>> I noticed also :
>>>
>>>  ./stest --session=foo 1
>>>  ./stest --session=foo 0
>>>
>>> Both processes are waiting in rt_sem_p . The first process catches SIGINT, the second doesn't. If you press CTRL+C on the second process it stops but also the first process is falling through the rt_sem_p although no rt_sem_v is raised.
>>
>>
>> Spurious wake up in the Cobalt kernel when aborting a sem wait operation
>> due to a signal/unblock event, that is the reason why I could not see
>> this from a Mercury setup. This is fixed in the -next branch.
>>
>>> At that moment no process is pending on rt_sem_p anymore. But if you do then a rt_sem_inquire, nwaiters is still 1.
>>
>> I don't observe this one. Assuming you enabled the registry, what does
>> /var/run/xenomai/.../alchemy/semaphores/semtestsem tell you about the
>> sema4 value?
>>
> 
> When I start my processes, I don't see this alchemy directory in my registry. Any suggestion why ?
> 
> The output of 'xeno-config --info' is :
> 
> Xenomai version: Xenomai/cobalt v3.0-rc5 -- 
> Linux dev-x10sae 3.18.12-x86-64-xeno-3.0.rc5 #1 SMP PREEMPT Fri Jul 10 12:29:14 CEST 2015 x86_64 GNU/Linux
> Kernel parameters: BOOT_IMAGE=/boot/vmlinuz-3.18.12-x86-64-xeno-3.0.rc5 root=UUID=fc8ecefa-fc73-487f-a045-cffa99c38a11 ro quiet console=tty0 console=ttyS0,115200n8
> I-pipe release #1 detected
> Cobalt core 3.0-rc5 detected

You should be running -rc6.

> Compiler: gcc version 4.9.2 (Debian 4.9.2-10) 
> Build args: --prefix=/usr --includedir=/usr/include/xenomai --mandir=/usr/share/man --with-testdir=/usr/lib/xenomai/testsuite --with-core=cobalt --enable-smp --enable-pshared --enable-registry --build x86_64-linux-gnu build_alias=x86_64-linux-gnu
> 
> I have only this in the registery :
> 
> find /var/run/xenomai
> 
> /var/run/xenomai
> /var/run/xenomai/root
> /var/run/xenomai/root/foo
> /var/run/xenomai/root/foo/6210
> /var/run/xenomai/root/foo/6203
> /var/run/xenomai/root/foo/system
> 
> 

FUSE services do not seem to be enabled, those directories are the mount
points created by sysregd, over which fuse-managed fs should be mounted.

Are you sure those directories are not left overs from a previous run,
and that you are actually running an executable built over the
configuration settings above?

This would confirm it:

$ <your-app-executable> --dump-config|grep REGISTRY

-- 
Philippe.