Re: [Xenomai-help] cannot make system() calls anymore

[Jan Kiszka <jan.kiszka@domain.hid>]

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Jerome Pasquero wrote:
> Hi,
> 
> I recently upgraded from xenomai 2.3.0 under linux 2.6.17.14 to the latest
> stable version of xenomai 2.4.1 under linux 2.6.23.12.
> Everything seems to be working just fine, except that I seem to  no longer
> be able to make system calls inside a real-time task. It simply freezes
> everything and I need to restart my computer.
> I don't know if it was just a fluke that it was working with 2.3.0 and that
> I am not supposed to do that at all. Could it be that I forgot to include an
> option when recompiling the kernel?

A system freeze is not a valid reaction of Xenomai on invalid user 
activity - unless that freeze just means one of your high-prio tasks 
decided to enter an endless loop. Have you already tried to enable the 
Xenomai watchdog?

> 
> Note that I have no problem making system calls from outside a real time
> task (for instance, right before a rt_task_shadow() call).
> Also, it seems that the problem only occurs when other libraries are used.
> For instance, if one compiles the code below with no other libraries than
> the xenomai libs (and stdc++), it works just fine:
> gcc  `/usr/xenomai/bin/xeno-config --xeno-cflags`
> `/usr/xenomai/bin/xeno-config --xeno-ldflags` -lstdc++ -lnative main.cpp
> 
> However, as soon as I add the libxml2 library, it crashes:
> gcc  -D_GNU_SOURCE -D_REENTRANT -D__XENO__  -I/usr/include/libxml2
> -I/usr/xenomai-2.4.1/include  -L/usr/local/lib -L/usr/xenomai-2.4.1/lib
> -lxml2 -lnative -lpthread `/usr/xenomai/bin/xeno-config --xeno-cflags`
> `/usr/xenomai/bin/xeno-config --xeno-ldflags` -lstdc++ -lnative main.cp
> 
> This is true with other libraries as well (e.g. gsl lib) but not of all
> libraries (for instance, it seems to work with the math library i.e. -lm)
> 
> Am I doing something wrong?
> In case you were wondering, I want to be able to make system calls from
> inside real time threads cause I want to load/unload realtime modules
> directly from my application. In the code snippet below, I am simply trying
> to do a  'ls'  command to keep it as simple as possible.

Thanks for the demo. This one already bricks your box? But only when 
linked against libxml?

> 
> Thanks for your help in advance.
> 
> 
> #include <iostream>
> #include <sys/mman.h>
> #include <signal.h>
> #include <native/mutex.h>
> #include <native/timer.h>
> #include <native/task.h>
> 
> void cleanup(int unused)
> {
>     // delete current task
>     rt_task_delete(NULL);
> }
> 
> int main(int argc, char *argv[])
> {
>     signal(SIGABRT, cleanup);
>     signal(SIGKILL, cleanup);
>     signal(SIGINT, cleanup);
>     signal(SIGTERM, cleanup);
>     signal(SIGHUP, cleanup);
>     signal(SIGALRM, cleanup);
> 
> 
>     RT_TASK mainTask;
> 
>     mlockall(MCL_CURRENT | MCL_FUTURE);
>     rt_task_shadow(&mainTask, "gui", 50, T_FPU);
> 
>     rt_task_sleep((RTIME) 1E9);
> 
>     system("ls"); // this is what causes the problem...

Ah, you mean "system" with system call - or actually any call of 
Standard-Linux kernel services?

In any case, let's first check for runaway threads with the watchdog.

Jan


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